Table of contents

The International MEMS conference (iMEMS2006) organized by the Institute of Bioengineering and Nanotechnology and Nanyang Technological University aims to provide a platform for academicians, professionals and industrialists in various related fields from all over the world to share and learn from each other. Of great interest is the incorporation of the theme of life sciences application using MEMS. It is the desire of this conference to initiate collaboration and form network of cooperation. This has continued to be the objective of iMEMS since its inception in 1997.

The technological advance of MEMS over the past few decades has been truly exciting in terms of development and applications. In order to participate in this rapid development, a conference involving delegates from within the MEMS community and outside the community is very meaningful and timely. With the receipt of over 200 articles, delegates related to MEMS field from all over the world will share their perspectives on topics such as MEMS/MST Design, MEMS Teaching and Education, MEMS/MST Packaging, MEMS/MST Fabrication, Microsystems Applications, System Integration, Wearable Devices, MEMSWear and BioMEMS. Invited speakers and delegates from outside the field have also been involved to provide challenges, especially in the life sciences field, for the MEMS community to potentially address. The proceedings of the conference will be published as an issue in the online Journal of Physics: Conference Series and this can reach a wider audience and will facilitate the reference and citation of the work presented in the conference.

We wish to express our deep gratitude to the International Scientific Committee members and the organizing committee members for contributing to the success of this conference. We would like to thank all the delegates, speakers and sponsors from all over the world for presenting and sharing their perspectives on topics related to MEMS and the challenges that MEMS can potentially address.

In this contribution we present the development of three microfabricated devices for the study of neuronal and cellular networks. Together, these devices form an attractive toolbox, which is useful to stimulate and record signals of both electrical and chemical nature. One approach consist of microelectrode arrays for the study of neuronal networks, and allow for the electrical stimulation of individual cells in the network, while the other electrodes of the array record the electrical activity of the remaining cells of the network. We also present the use of micropipettes that can measure the extra- and intracellular concentrations of ions in cells cultures. A third approach exploits the laminar flows in a microfluidic device, to deliver minute amounts of drug to some cells in a cellular network. These three illustrations show that microfabricated platforms are appealing analytical tools in the context of cell biology.

The ability to use charge transporting proteins such as bacteriorhodopsin in the building of data storage and transmission devices for use in computer technology is explored. Designs of mutants that lead to proteins that are more stable thermally and more efficient at data processing requires knowledge of the elctrostatics/dynamics of the molecules. We find that both the motions and the electrostatics are strongly effected when the influence of neighbouring molecules in the assembly are included, underscoring the importance of inclusion of the assemblies explicitly in computer models.

SSLS' technology basis in micro/nanofabrication encompasses the full LIGA process in a class 1000 cleanroom. This technology is used for an R & D programme and for foundry-type work for commercial customers. R & D achievements include the development of the first electromagnetic metamaterials for the terahertz spectral range up to the near infrared. Complementing micro/nanofabrication, SSLS is exploiting its portfolio of synchrotron radiation methods for the characterisation of key properties of the micro/nanodevices as exemplified by the infrared spectroscopy of the THz electromagnetic metamaterials or of diffractive optical elements for Fourier transform spectroscopy.

The laser ablation is widely used for the formation of metal nanoparticles, nanorods, nanodisks, nano-networks and polymeric microchannels. This paper reviews the results obtained when using of the microablation of the gold layers that are tens of nanometer think deposited on various transparent surfaces, such as Poly(tert-butyl methacryalate), Poly(methyl methacrylate) -PMMA, Polydioxymethyl siloxane, PDMS, and glass, with a low power laser (low fluences of 4-500 µJ/cm2, 337nm wavelength and 4ns pulses). The microablation results in the preferential formation of gold wire-like nanostructures at the edges and across the ablated channels on PMMA and PTBMA; and of gold nanoparticles on glass and PDMS. This contrasting behavior is explained by the presence of gas-generating pyrolysis on PMMA or PTBMA as opposed to lack of it on glass and PDMS.

This paper presents a new electromagnetic modelling approach for the design of GaAs membrane supported monolithically integrated mm-wave receivers. The receivers structures are divided into membrane supported sections and bulk GaAs supported sections. Each block is modelled and designed using the full-wave electromagnetic simulation software Zeland IE3D. The Schottky diode is included in the model using the internal port feature. The design steps include the Schottky diode experimental characterization, design and measurements of membrane supported antenna demonstrators and linear/nonlinear simulations of the final receiver structures. The fabrication processes is based on GaAs micromachining. Two types of video detection receivers were designed, fabricated and tested: a 38 GHz double folded slot antenna receivers and a 45 GHz Yagi-Uda antenna receiver. Both circuits monolithically integrated the antenna with the Schottky diode on the same 2.2 µm thin semiinsulating GaAs membrane. The experimental results demonstrate an isotropic voltage sensitivity of 3000 mV/mW at 38 GHz and 6000 mV/mW at 45 GHz, respectively. The measurements validate the modelling approach and open a window of opportunity for the development of innovative RF MEMS architectures operating at higher frequency, up to the sub-millimetre wave frequency range.

The interest in micro- and nanotechnologies has grown rapidly in the last years. The applications are versatile and different techniques found its way into several research domains as optics, electronics, magnetism, fluidics, etc. In all of these fields integration of more and more functions on steadily decreasing device dimensions lead to an increase in structural density and feature size. Expensive and slow processes utilizing projection steppers or e-beam direct writer equipment are used to fabricate nm features today. A high throughput and cost effective method adapted on a standard mask aligner will be demonstrated, making features of below 300nm available on wafer-level. We will demonstrate results of 4 different resists exposed on a DUV proximity aligner and plasma etched for optical and biological applications in the sub-300nm range.

This paper reports on a new method for estimation and minimization of mechanical stress on MEMS sensor and actuator structures due to packaging processes based on flip chip technology. For studying mechanical stress a test chip with silicon membranes was fabricated. A network of piezo-resistive solid state resistors created by diffusion was used to measure the surface tension pattern between adjacent membranes. Finite element method simulation was used to calculate the stress profile and to determine the optimum positions for placing the resistive network.

This paper proposes a T-shaped micromixer featuring 45° parallelogram barriers within the mixing channel. The proposed device obtains a rapid mixing of two sample fluids by means of the electrokinetic instability induced by shedding effect which is produced as an appropriate intensity of DC electric field of is applied. The proposed device uses a single high-voltage power source to simultaneously drive and mix the sample fluids. The effectiveness of the mixer is characterized experimentally as a function of the applied electrical field intensity and the extent to which the parallelogram barriers obstruct the mixing channel. The experimental results indicate that the mixing performance reaches 91.2% at a cross-section located 2.3 mm downstream of the T-junction when the barriers obstruct four-fifths of the channel width and an electrical field of 300V/cm is applied. The micromixing method presented in this study provides a simple low-cost solution to mixing problems in lab-on-a-chip systems.

Using simple and reliable microfabrication techniques, this study develops a capillary electrophoresis (CE) microchip with 3-dimensional-structured (3D-structured) contactless capacitive detector electrodes mounted parallel to the separation channel. The offchannel electrodes are deposited by Au sputtering and patterned using a standard 'lift-off'' process. A vacuum fusion bonding process is employed to seal the lower substrate containing the microchannels and electrodes to an upper glass cover plate. The variation in the capacitance between the electrodes in the side channels is measured as different samples and ions pass through the detection region of the CE separation channel. Samples of Rhodamine B and a commercial sports drink are mixed in different buffer solutions and successfully separated and detected using the developed device. The 3D-structured contactless capacitive-type detection device has microscale dimensions and provides a valuable contribution to the realization of the lab-on-a-chip concept.

This paper describes a precision closed-loop driving scheme for Silicon Micromachined Vibratory Gyroscope (SMVG). It decouples the angle and gain of the selfoscillation- driven, optimizes the angle to reduce the relative difference between drive frequency and resonant frequency of the drive mode and achieves the closed-loop selfoscillation- driven by nonlinear relation between DC voltage using for control and drive force. The experiments show that the standard deviation of drive frequency is 0.009Hz, with relative drift 2.2ppm and the standard deviation of the amplitude is 0.0025mV, with relative drift 15ppm in one hour respectively. The closed-loop drive scheme improves the precision and stability of drive frequency and the amplitude of the gyroscope well. The paper analyses and tests the noise of the self-oscillation-driven. The result shows that the self-oscillation-driven has a rms noise below -100dB.

Nanoimprint Lithography is a well-acknowledged low cost, high resolution, large area 3D patterning process for polymers. It includes the most promising methods: high pressure hot embossing (HE) and UV-Nanoimprint Lithography (UV-NIL). Curing of the imprinted structures is either done by cooling down below the glass transition temperature of the thermoplastic polymer in case of HE or by subsequent UV-light exposure and cross-linking in case of UV-NIL. Both techniques allow rapid prototyping for high volume production of fully patterned substrates for a wide range of materials. The advantages of using polymer substrates over common Micro-Electro-Mechanical Systems (MEMS) processing materials like glass, silicon or quartz are: bio-compatible surfaces, easy manufacturability, low cost for high volume production, suitable for use in micro- and nano-fabrication, low conductivity, wide range of optical properties just to name a few. We will present experimental results on HE processes with PMMA as well as UV-NIL imprints in selected UV-curable resists.

In the second part of the work we will describe the bonding techniques for packaging of the micro or nano structures. Packaging of the imprinted features is a key technology for a wide variety of field of applications: µ-TAS, biochemistry, micro-mixers, micro-reactors, electrophoresis cells, life science, micro-optical and nano-optical applications (switches) nanofluidics, data storage, etc. for features down to sub-100 nm range. Most bonding techniques for polymer use adhesives as intermediate layers. We will demonstrate a promising technique for dense and very strong bonds using plasma activation of polymers and glass. This bonding technology allows for bonding at low temperatures well below the glass transition temperature of the polymers, which will ensure that the structures are not deformed.

This paper presents for the first time a design methodology for MEMS/NEMS based on haptic sensing technologies. The software tool created as a result of this methodology will enable designers to model and interact in real time with their virtual prototype. One of the main advantages of haptic sensing is the ability to bring unusual microscopic forces back to the designer's world. Other significant benefits for developing such a methodology include gain productivity and the capability to include manufacturing costs within the design cycle.

In this paper, we demonstrate a silicon-based packaging platform for a package component of Light Emitting Diode (LED) using silicon bulk micromachining technique and using the silicon substrate with embedded solder interconnections to dissipate heat and the match thermal expansion coefficient (CTE). The objective is to develop an LED package that can overcome life time, high operating voltage, package degradation and has the ability to drive the devices at higher power and higher brightness. The results reported in before show that the silicon substrate can enhance heat removal for safe junction temperature operation and minimize thermal stress caused by mismatch of CTE. Moreover, silicon-based packaging platform with embedded solder interconnections has been fabricated in this study, and this technique can be used for packaging conventional optoelectronic semiconductor devices such as laser diode or MEMS devices.

The purpose of this research was to model, design and fabricate a biodynamic analysis microsystem required for determination of various molecular transport properties of the biological fluids. In order to achieve this, a lab-on-a-chip device was fabricated. The microfluidic system developed satisfies the objectives for the study of microcirculation and characterization of cell rheological properties, functions and behaviour. The measurement principle of the viscosity of biological fluids is based on the detection of the rotation of a polysilicon gear-wheels system. The gear-wheels have external diameters of 250 µm, 200 µm, 160 µm and 3 µm thickness. The micromachining process combines the undercut and refill technique with pin-joint bearing permitting the fabrication of bushings that were used to elevate the rotor away from the silicon surface. The testing of the microfluidic dynamic system was performed using electromagnetic micropumps and magnetic controllers. Each device was fabricated by silicon micromachining technology and tested to obtain the specific characteristics.

Thermal dependency of material characteristics in micro electromechanical systems strongly affects their performance, design, and control. Hence, it is essential to understand and model that in MEMS devices to optimize their designs. A thermal phenomenon introduces two main effects: damping due to internal friction, and softening due to Young modulus temperature relation. Based on some reported theoretical and experimental results, we model the thermal phenomena and use two Lorentzian functions to describe the restoring and damping forces caused by thermal phenomena. In order to emphasize the thermal effects, a nonlinear model of the MEMS, by considering capacitor nonlinearity, have been used. The response of the system is developed by employing multiple time scales perturbation method on nondimensionalized form of equations. Frequency response, resonant frequency and peak amplitude are examined for variation of dynamic parameters involved.

This paper present a new type of electroplating Nickel micromachined probes with out-of-plane predeformation for the next generation integrated circuit (IC) chip testing probe card application. It was fabricated using silicon bulk etching, Ti deposition and Ni electroplating process. We use the residual stress effect of thin films deposition to cause the flexible micromachined probe with a large out-of-plane predeformation and combine postelectroplating technique to further increase beam's thickness and therefore enhance its stiffness. The typical micromachined probe had a thickness 5∼10 µm, a width of 20 µm, and a length of 100 µm. The maximum deflection of the fabricated Nickel probe beam was 28 µm. This micromachined probe is capable of providing a very larger number of testing probe card, including the array pad format, and this designed also to satisfy the requirements for high frequency, high resolution and low cost wafer-level testing...

The focus of this paper is to describe emerging techniques and methods for interface circuit design for frequency, period, duty-cycle or PWM output MEMS sensors. The designed module is intended for frequency-time parameters - to - digital conversion and communication functions and can be embedded into a SoC. The developed interface circuit provides technologies that both reduce the cost and time of SoC development and improve sensor system performance. Its revolutionary suite of technical products facilitates, for the first time, low-cost, time-efficient production of MEMS sensor applications. On the other hand the proposed design approach reduces the development time, risk and cost of sensor applications by to ten times.

This paper presents a numerical model for simulation of two-dimensional moving-interface flow of non-Newtonian fluid under non-isothermal conditions. The level-set method is used to capture the moving interface implicitly. The finite volume method is used to solve the governing equations and the level-set equations. The development of the moving interface is simulated successfully. The velocity and temperature profiles are also investigated.

A novel method to manufacture and assemble a microinductor that is based on flipchip bonding is described in this paper. The fabricated inductors have an inductance ranging from 0.3 µH to 180 µH. An optimum Q-factor of 14 was attained at 1MHz. Cobalt-Copper-iron cores maintained a constant inductance across a 1 kHz-1MHz bandwidth. The thin film laminate minimizes the eddy current loss and the hysteresis loss was negligible. Impedance increases linearly with frequency indicating that parasitic capacitance effects in this frequency range are negligible. The microinductor operated at an efficiency of 92% at 1MHz achieving a power density of 3.75 W/mm³.

This paper analyses the deformation of a double-walled nanotube-based nanoelectromechanical switch. The product of Young's modulus and moment of inertia of the tube is determined by a molecular dynamics simulation with a linear deflection approximation. The switch is simplified to a beam system, and the loading is calculated from three coupled energy domains: the electrostatic energy domain, the elastostatic energy domain, and the van der Waals energy domain. A meshless formulation is then used to discretize the switch to establish the non-linear system of equations for analysis. A parametric comparison with the results in the literature showed that the method developed in this paper is very effective.

Presented herein are the design, modelling, fabrication and testing of a MEMSbased capacitive bending strain sensor utilizing a comb drive. This sensor is designed to be integrated with a telemetry system that will monitor changes in bending strain to assist orthopaedic surgeons with the diagnosis of spinal fusion. ABAQUS/CAE version 6.5 finite element analysis (FEA) modelling software was used to predict sensor actuation, capacitance output and the avoidance of material failure. Highly doped boron silicon wafers with a low resistivity were fabricated into an interdigitated finger array employing deep reactive ion etching (DRIE) to create 150 µm sidewalls with 25 µm spacing between the adjacent fingers. For testing, the sensor was adhered to a steel beam, which was subjected to four-point bending. This mechanically changed the spacing between the interdigitated fingers as a function of strain. As expected, the capacitance output increased as an inverse function of the spacing between the interdigitated fingers, beginning with an initial capacitance of 7.56 pF at the unstrained state and increasing inversely to 17.04 pF at 1571 µε of bending strain. The FEA and analytical models were comparable with experimental data. The largest differential of 0.65 pF or 6.33% occurred at 1000 µε.

We have measured the flow field inside microdroplets formed by two immiscible fluids in a microchannel using micro particle image velocimetry (micro-PIV) technique. An aqueous liquid with fluorescent particles was injected in an immiscible carrier flow. Both velocity fields during the droplet formation process and during the passage in straight, rectangular microchannels were measured and evaluated. We observed that at a certain layer the direction of the outer circulation flow in the droplet is the same as that of the droplet motion. The results indicate that the immiscible carrier fluid flows through the gaps between the aqueous droplet and the rigid channel wall at a velocity faster than the droplet itself.

This paper reports an analytical model, the fabrication and the characterization of a polymeric micromixer based on Taylor dispersion. Due to the distributed velocity field over the channel cross section, the effective dispersion in axial direction in a microchannel is much stronger than the pure molecular diffusion. In our work, squential segmentation was used in the micromixer for improving mixing in a microchannel. The micromixer was designed and fabricated based on lamination of five 100-µm-thick polymer sheets. Rubber valve seats were embedded between the forth and the fifth layers. The polymer layers were machined using a CO₂ laser. The lamination of the five layers was carried out by a commercial hot laminator (Aurora LM-450HC). External solenoid actuators are used for closing the valves at the mixer inlets. The experimental results confirm the effect of Taylor dispersion. Mixing ratio can be adjusted by pulse width modulation of the control signal of the solenoids.

In this paper, performance evaluation of miniature heat pipes in LTCC was made by numerical analysis, and the optimum miniature heat pipe design was defined. The effect of the groove depth, width and vapor space on the heat transfer capacity of miniature heat pipes was analyzed. Prototypes of the miniature heat pipes in LTCC were fabricated. Preliminary charging, sealing and thermal measurement of the miniature heat pipes were performed, and the challenges were discussed.

The measurement of the rotation of rigid solids is of considerable interest in a number of areas. Rotation detectors are not only used in aircraft, missiles etc. military fields have also been developed for new civil fields such as automobile navigation, antenna stabilization, crane control, unmanned vehicle control, wind and renewable energy platform stabilization. In this paper, the fundamental operations of fiber-optic gyroscopes are reviewed. Performance-limiting phenomena are discussed along with methods to reduce their effect on the rotation-rate signal. Current technology and performance of new demodulate systems are presented applicable to MEMS technology. The FOG with scanning phase-shift demodulates technology based on anti-noise filter circuit improvement of DSP algorithm is proposed in this paper. New methods, which are used to fabricate the nanometer optical fiber, are discussed.

Oxygen plasma treatment has been used extensively to bond polydimethyl siloxane to polydimethyl siloxane or glass in the rapid prototyping of microfluidic devices. This study aimed to improve the bonding quality of polydimethyl siloxane to passivated silicon using oxygen plasma treatment, and also to evaluate the bonding quality. Four types of passivated silicon were used: phosphosilicate glass, undoped silicate glass, silicon nitride and thermally grown silicon dioxide. Bonding strength was evaluated qualitatively and quantitatively using manual peel and mechanical shear tests respectively. Through peel tests we found that the lowering of plasma pressure from 500 to 30 mTorr and using a plasma power between 20 to 60 W helped to improve the bond quality for the first three types of passivation. Detailed analysis and discussion were conducted to explain the discrepancy between the bonding strength results and peeling results. Our results suggested that polydimethyl siloxane can be effectively bonded to passivated silicon, just as to polydimethyl siloxane or glass.

In this paper we describe a robust design method for microelectromechanical systems (MEMS) subject to inherent geometric and material uncertainties. We propose to formulate the robust MEMS design with variability problem as a specific optimization problem, namely chance-constrained posynomial programming, in which the statistical variations of both the process parameters and design variables can be easily incorporated. Using such constrained optimization approach, automated robust design can be obtained with very suboptimal design cost, and parametric yield of each specification can be guaranteed. Finally, the method is illustrated by considering the example of a simple crab-leg resonator.

This paper reports a design to compensate overlapping area reduction in MEMS Micromirror. The electromechanical behavior of a 300x300 m mirror actuated by electrostatic comb drive is simulated by CoventorWare™. The interdigitated fingers are 240 µm long and 20 µm wide separated by 20 µm gap. The displacement of the mirror is compared when the frame of stator is released and fixed. The simulation shows that released-frame stator produces more displacement in z direction than fixed-frame stator by the factor of 3 when 50V DC voltage is applied. The improvement in micromirror actuation is as a result of the increase of overlapping area provided by curl compensation with released-frame approach. Therefore, the released-frame design is a promising method to reduce input voltage and enhance efficiency of electrostatic comb drive micromirror.

The nonlinear electrostatic pull-in behaviour of MEMS Switches in micro-electromechanical systems (MEMS) is investigated in this article. We used the distributed model when the electrostatic pressure didn't apply at the whole of the beam and applied only in the mid-part of the beam. In this part the electrostatic area is different from two other parts. The model uses Euler-Bernoulli beam theory for fixed-fixed end type beams. The finite difference method was used to solve the nonlinear equation. The proposed model includes the fringing effects of the electrical field, residual stress and varying electrostatic area effects. The numerical results reveal that the profile deflection of the MEMS Switch may not only influence the distribution of the electrostatic force but also considerably change the nonlinear pull-in voltage.

We report a novel fabrication method for the microneedle array with a 3-dimentional feature and its replication method; ''Hot-pressing'' process with bio-compatible material, PLLA (Poly L-LActide). Using inclined deep X-ray exposure technique, we fabricate a band type microneedle array with a single body on the same material basement. Since the single body feature does not make adhesion problem with the microneedle shank and basement during peel-off step of a mold, the PMMA (Poly-Methyl-MethAcrylate) microneedle array mold insert can be used for mold process which is used with the soft material mold, PDMS (Poly-Di- Methyl-Siloxane). The side inclined deep X-ray exposure also makes complex 3-dimentional features by the regions which are not exposed during twice successive exposure steps. In addition, the successive exposure does not need an additional mask alignment after the first side exposure. The fabricated band type microneedle array mold inserts are assembled for large area patch type out-of-plane microneedle array. The bio-compatible microneedle array can be fabricated to the laboratory scale mass production by the single body PMMA mold insert and ''Hot-pressing'' process.

The ''gold'' standard in the study of ionic currents across biological membranes is the Patch Clamp method. However, this is a slow, labor and skill intensive process. High throughput patch clamp devices are mainly chip-based. A major challenge in these miniaturized devices is the low rate of ''Gigaseal'' formation which is critical in the study of Single Channel effect. In a conventional patch clamp, a pipette moves and patches a fixed cell (cell-adhered patch) which is grown on the bottom of a Petri dish. In the chip-based case, the cells are in suspension and move towards the fixed patch clamp sites (cell-suspended patch). In this study, using the proven conventional patch clamp setup, we investigated the effect of the differences in the cell configurations between the convention patch clamp and cell-based patch clamp. It is shown that adhered cells (as used in the conventional setup) have a much higher rate of gigaseal formation as compared to the cells in suspension (as used in chip-based devices). We postulate that the arrangement of the cytoskeleton within the cell plays a major part in the formation of the gigaseal.

A Capacitive Micromachined Ultrasonic Transducers simulation database, based on electromechanical coupling theory, has been fully developed for versatile capacitive microtransducer design and analysis. Both arithmetic and graphic configurations are used to find optimal parameters based on serial coupling simulations. The key modeling parameters identified can improve microtransducer's character and reliability effectively. This method could be used to reduce design time and fabrication cost, eliminating trial-and-error procedures. Various microtransducers, with optimized characteristics, can be developed economically using the developed database. A simulation to design an ultrasonic microtransducer is completed as an executed example. The dependent relationship between membrane geometry, vibration displacement and output response is demonstrated. The electromechanical coupling effects, mechanical impedance and frequency response are also taken into consideration for optimal microstructures. The microdevice parameters with the best output signal response are predicted, and microfabrication processing constraints and realities are also taken into consideration.

Drug screening at cellular level has becomes an attractive field of research. Different researchers have tried to record cellular response to drugs by electrical or optical approach using both invasive and non-invasive methods. Silicon-based microelectrode integrated microchips are useful tools for in situ temporal recording of neurotransmitter releasing from neural cells. A microfabricated electrochemical biochip is presented in this paper. Using dopaminergic cells grown on the chip, the dopamine excytosis can be electrochemical amperomatric detected non-invasively from drug incubated dopaminegic cells by the microelectrode integrated on chip. This silicon-based electrochemical chip has been designed with an electrode array located on the cell culture chamber bottom. Each electrode is individually electrical controlled. MN9D and PC12 dopaminergic cell lines have been demonstrated on this chip for drug effects study. This silicon-based electrochemical microchip provides a non-invasive, in situ, temporal detection of dopamine exocytosis from dopaminegic cells, and holds the potential for applications in studying the mechanisms of dopamine exocytosis and drug screening. It is also extendable for other cell culture and drug effects study.

A label free and sensitive DNA/RNA silicon based electrochemical microsensor array was developed by using thin film of the conducting polymer polypyrrole doped with an oligonucleotide probe. The electrochemical potential pulse amperometry technique was used for a biowarfare pathogen target DNA detection. The electrical potential assistanted DNA hybridisation method was applied. The sensor signal was increased by increasing the electrical potential assistanted DNA hybridisation time. It was possible to detect 0.34pmol and 0.072fmol of complementary oligonucleotide target in 0.1ml in seconds by using unpolished and polished gold electrode respectively. The probe preparation was also in seconds time, comparing indirect electrochemical DNA sensor, it has a fast sensor preparation as well as sensor response and label free advantages. The silicon microfabrication technique was used for this sensor array fabrication, which holds the potential to integrate with sensor electrical circuits. The conducting polymer polypyrrole was electrochemically deposited on each electrode respectively which has a possibility to dope the different DNA probe into the individual electrode to form a sensor array.

In this paper we present the design and process optimization for fabricating piezoresitive pressure sensor and MOSFET Differential Amplifier simultaneously on the same chip. Silicon On Insulator approach has been used for realizing the membrane as well as the electronics on the same chip. The amplifier circuit has been configured in the common source connection and it has been designed with PSPICE simulation to achieve a voltage gain of about 5. In the initial set of experiments the Pressure sensor and the amplifier were fabricated on separate chips to optimize the process steps and tested in the hybrid mode. In the next set of experiments, SOI wafer having the SOI layer thickness of about 11 microns was used for realizing the membrane by anisotropic etching from the backside. The piezo-resistive pressure sensor was realized on this membrane by connecting the polysilicon resistors in the form of a Wheatstone bridge. The MOSFET source follower amplifier was also fabricated on the same SOI wafer by tailoring the process steps to suit the requirement of simultaneous fabrication of piezoresistors and the amplifier for achieving MOSFET Integrated Pressure Sensor. Reproducible results have been achieved on the SOI wafers, with the process steps developed in the laboratory. Sensitivity of 270 mV /Bar/10V, with the on chip amplifier gain of 4.5, has been achieved with this process.

It is generally accepted that the piezo-resistive coefficient in single crystal silicon is higher when P-type impurities such as boron are used for doping the resistors. In this paper we demonstrate that the sensitivity of polycrystalline silicon piezo-resistive pressure sensors can be enhanced considerably when phosphorus diffusion source is used instead of boron dopant for realizing the piezo-resistors. Pressure sensors have been designed and fabricated with the polycrystalline piezo-resistors connected in the form of a Wheatstone bridge and laid out on thermal oxide grown on membranes obtained with a Silicon On Insulator (SOI) approach. The SOI wafers required for this purpose have been realized in-house by Silicon Fusion Bonding (SFB) and etch back technique in our laboratory. This approach provides excellent isolation between the resistors and enables zero temperature coefficient of the polysilicon resistor. The results obtained in our laboratory have clearly demonstrated that by optimizing the phosphorus diffusion temperature and duration, it is possible to achieve sensitivities in excess of 20mV /Bar for bridge input voltage of 10V, with linearity within 1% over a differential pressure range up to 10Bar (10 ⁶Pascal), and burst pressure in excess of 50 Bar as compared to the 10mV /Bar sensitivity obtained with boron doped polysilicon piezo-resistors. This enhancement is attributed to grain boundary passivation by phosphorous atoms.

Thermal management modelling and simulations of a polymerase chain reaction (PCR) device to be integrated on a lab on chip (LOC) have been carried out and presented. A typical MEMS PCR in symmetrical configuration is the base model for this study. When the PCR device is integrated on a fluidic chip with many other bio-analysis components such as DNA extraction, RNA extraction, electro-chemical sensor, flow through components and channels etc., thermal symmetry required for uniform temperature across the PCR chamber is normally lost. In this paper, ANSYS 8.0 simulations in varying conditions and corresponding physical basis have been investigated and presented. Model optimizations are carried out when PCR chamber is placed, one, in the centre (symmetry) and two, in the corner (asymmetry) of the integrated chip. In both cases, temperature uniformity within ±0.5 °C variation is obtained.

This contribution presents a Distributed MEMS Transmission Line (DMTL) phase shifter designed for 24 GHz and fabricated in Silicon-Bulk Micromechanic Technology. Using this technology enables to commonly suspend all capacitive loads on one movable plate and allows full range analog and homogeneous gap adjustment. The first available prototypes of the phase shifter are characterized to provide 5.4 °/mm differential phase shift at 24 GHz and to show 0.1 dB/mm insertion loss. An asymmetric coplanar signal coupler with a center frequency of 24 GHz and 10% bandwidth is used to contact the signal through the substrate of the phase shifter chip and back to a supporting printed circuit board. The normalized measured insertion loss of the coupling structure after simulated optimization is 0.13 dB - 0.17 dB.

This paper presents a MEMS reliability study methodology based on the novel concept of 'virtual prototyping'. This methodology can be used for the development of reliable sensors or actuators and also to characterize their behaviour in specific use conditions and applications. The methodology is demonstrated on the U-shaped micro electro thermal actuator used as test vehicle. To demonstrate this approach, a 'virtual prototype' has been developed with the modeling tools MatLab and VHDL-AMS. A best practice FMEA (Failure Mode and Effect Analysis) is applied on the thermal MEMS to investigate and assess the failure mechanisms. Reliability study is performed by injecting the identified defaults into the 'virtual prototype'. The reliability characterization methodology predicts the evolution of the behavior of these MEMS as a function of the number of cycles of operation and specific operational conditions.

Bio-Micro Electro Mechanical Systems/Nano Electro Mechanical Systems include a wide variety of sensors, actuators, and complex micro/nano devices for biomedical applications. Recent advances in biosensors have shown that sensors based on bending of microfabricated cantilevers have potential advantages over earlier used detection methods. Thus, a simple cantilever beam can be used as a sensor for biomedical, chemical and environmental applications. Here, microfabricated multilayered cantilever beam is exposed to sensing environment. Lower layer being pure structural silicon or polymer and upper layer is of polymer with antigen/antibody immobilized in it. Obviously, it has an affinity towards its counterpart i.e. antibody/antigen. In the sensing environment, if counter elements exists, they get captured by this sensing beam head, and the cantilever beam deflects. This deflection can be sensed and the presence of counter elements in the environment can be predicted. In this work, a finite element model of a biosensor for sensing antibody/antigen reaction is developed and simulated using ANSYS/Multiphysics. The optimal dimensions of the microcantilever beam are selected based on permissible deflection range with the aid of MATLAB. In the model analysis, both weight and surface stress effects on the cantilever are considered. Approximate weights are taken into account because of counter elements, considering their molecular weight and possible number of elements required for sensing. The results obtained in terms of lateral deflection are presented.

Micro-Electro-Mechanical Systems (MEMS) technology has been identified as one of the most promising technologies in the 21st century. MEMS technology has opened up a wide array of unforeseen applications. Hence it is necessary to train the technocrats of tomorrow in this emerging field to meet the industrial/societal demands. The drive behind fostering of MEMS technology is the reduction in the cost, size, weight, and power consumption of the sensors, actuators, and associated electronics. MEMS is a multidisciplinary engineering and basic science area which includes electrical engineering, mechanical engineering, material science and biomedical engineering. Hence MEMS education needs a special approach to prepare the technocrats for a career in MEMS. The modern education methodology using computer based training systems (CBTS) with embedded modeling and simulation tools will help in this direction. The availability of computer based learning resources such as MATLAB, ANSYS/Multiphysics and rapid prototyping tools have contributed to proposition of an efficient teaching-learning framework for MEMS education presented in this paper. This paper proposes a conceptual framework for teaching/learning MEMS in the current technical education scenario.

This paper presents an approach for modeling and simulation of a new 2D acceleration sensor array using SystemC-AMS. The sensor array consists of six single acceleration sensors with different detection axes. These single sensors comprise of four capacitive segments and one mass segment, aligned in a semicircle. The redundant sensor information is used for offset correction.

Modeling of the single sensors is achieved using sensor structure simplification into 11 points and analytic equations for capacity changes, currents and torques. This model was expanded by a PWM feedback circuit to keep the sensor displacement in a linear region. In this paper the single sensor model is duplicated considering different positions of the seismic mass resulting in different detection axes for the single sensors. The measured accelerations of the sensors are merged with different weights depending on the orientation. This also reduces calculation effort.

Design, fabrication and preliminary testing of a flat pump with millimetre thickness are described in this paper. The pump is entirely made of polymer materials barring the magnet and copper coils used for electromagnetic actuation. The fabrication is carried out using widely available microelectronic packaging machinery and techniques. Therefore, the fabrication of the pump is straightforward and inexpensive. Two types of prototypes are designed and built. One consists of copper coils that are etched on an epoxy plate and the other has wound insulated wire of 90 µm diameter to serve as a coil. The overall size of the first pump is 25 mm × 25 mm × 3.6 mm including the 3.1 mm-thick NdFeB magnet of diameter 12 mm. It consists of a pump chamber of 20 mm × 20 mm × 0.8 mm with copper coils etched from a copper-clad epoxy plate using dry-film lithography and milled using a CNC milling machine, two passive valves and the pump-diaphragm made of Kapton film of 0.089 mm thickness. The second pump has an overall size of 35 mm × 35 mm × 4.4 mm including the magnet and the windings. A breadboard circuit and DC power supply are used to test the pump by applying an alternating square-wave voltage pulse. A water slug in a tube attached to the inlet is used to observe and measure the air-flow induced by the pump against atmospheric pressure. The maximum flow rate was found to be 15 ml/min for a voltage of 2.5 V and a current of 19 mA at 68 Hz.

In this paper, we present a novel analytical formulation for the coupled partial differential equations governing electrostatically actuated constrained elastic structures of inhomogeneous material composition. We also present a computationally efficient numerical framework for solving the coupled equations over a reference domain with a fixed finiteelement mesh. This serves two purposes: (i) a series of problems with varying geometries and piece-wise homogeneous and/or inhomogeneous material distribution can be solved with a single pre-processing step, (ii) topology optimization methods can be easily implemented by interpolating the material at each point in the reference domain from a void to a dielectric or a conductor. This is attained by considering the steady-state electrical current conduction equation with a 'leaky capacitor' model instead of the usual electrostatic equation. This formulation is amenable for both static and transient problems in the elastic domain coupled with the quasi-electrostatic electric field. The procedure is numerically implemented on the COMSOL Multiphysics® platform using the weak variational form of the governing equations. Examples have been presented to show the accuracy and versatility of the scheme. The accuracy of the scheme is validated for the special case of piece-wise homogeneous material in the limit of the leaky-capacitor model approaching the ideal case.

This paper is a brief report of plasma etching as applied to pattern transfer in silicon. It will focus more on concept overview and strategies for etching of tapered features of interest for MEMS and Wafer Level Packaging (WLP). The basis of plasma etching, the dry etching technique, is explained [1] and plasma configurations are described elsewhere [2][3]. An important feature of plasma etching is the possibility to achieve etch anisotropy. The plasma etch process is extremely sensitive to many variables such as mask material, mask openings and more important the plasma parameters.

This paper attempts to prove the feasibility of high temperature MEMS hot-wire anemometer for gas turbine environment. No such sensor exists at present. Based on the latest improvement in a new type of Polymer-Derived Ceramic (PDC) material, the authors present a Novel design, structural and thermal analysis of MEMS hot-wire anemometer (HWA) based on PDC material, and show that such a sensor is indeed feasible. This MEMS Sensor is microfabricated by using three types of PDC materials such as SiAlCN, SiCN (lightly doped) and SiCN (heavily doped) for sensing element (hot-wire), support prongs and connecting leads respectively. This novel hot wire anemometer can perform better than a conventional HWA in which the hot wire is made of tungsten or platinum-iridium. This type of PDC-HWA can be used in harsh environment due to its high temperature resistance, tensile strength and resistance to oxidation. This HWA is fabricated using microstereolithography as a novel microfabrication technique to manufacture the proposed MEMS Sensor.

Multi-liquid flow, such as one liquid displacing another liquid, is frequently encountered in practice. This can be achieved by electroosmotic (EO) pumping, which has its own unique characteristics and advantages. This investigation is on EO-driven, two-liquid displacement flow in a microcapillary. A theoretical model was developed to take into consideration the axial step change of velocity flow fields at the time-dependent liquid/liquid interface, continuity requirement, and induced local pressure gradients. The electrical current monitoring method was employed to measure the flowrate and subsequently determine the capillary zeta potentials which are required for the model prediction. The nonlinear change of the electrical current with time under a constant applied voltage was observed during the displacement process. The theoretical and experimental results validated the hypothesis that the non-uniform zeta potential and electric field induce local pressure gradients in the two different liquids. Our experimental results indicated that the time of displacement, and thus the flow velocity, is found to be dependent on the displacing flow direction, which has hitherto not been reported in the literature. The underlying mechanisms were postulated, but demand further investigation.

Numerical studies of subsonic gas flow through micro-thruster as no-slip benchmark problem and high speed gas flow through short micro-channel with slip and temperature jump correction have been carried out by solving two dimensional compressible Navier-Stokes (NS) system of equations. A 2-D explicit finite volume (FV) flow solver has been developed using modified advection upwind splitting methods (AUSM+) to achieve the solution of micro-scale gas flow having high resolution shock capturing ability. The results obtained are compared with published 1-D numerical, Direct Simulation Monte Carlo (DSMC) and 2-D Finite element (FEM) results. This study utilizes the robustness and accuracy of AUSM+ and FVM to predict the micro-scale gas flows with simple explicit time marching, ranging from subsonic to supersonic flow.

This paper aims at developing Parts Synthesis Approach (PSA) for three-dimensional integration of MEMS and Microsystems leading to System-On-Package (SOP). This eliminates the interconnection related problems that arise when MEMS and its associated circuitry are packaged separately. A gas sensor array microsystem illustrates this. The novelty is that the electronics block at room temperature and the sensor at sensing temperature (250° C - 550° C) coexist in the same SOP. Targeted specifications of the SOP are low power budget per sensor and low cost. Thermal and structural modelling and analysis has been done using ANSYS software. The SOP is modular in design and construction.

In PSA the six physical parts of the SOP are first designed, optimized and fabricated individually and then integrated to form the desired SOP. The substrate is an integral and active part of the SOP. Power management is done by reducing thermal mass of the hotplate, increasing thermal resistance between the hotplate and the rest of the substrate and using pulsed power operation. Designs of the cavity structure, the coverlid and the bottom support help in thermal management. This technique circumvents the difficulties of forming deep cavities in LTCC technology. Since the six different parts of the SOP are fabricated separately and then integrated together the final yield is high. Designing in parallel reduces required time and cost.

A low actuation voltage and no contact stiction are important factors in applying micro-electro-mechanical-system (MEMS) RF switches to mobile communication devices. Conventional electrostatic RF MEMS switches require several tens of voltages for actuation. In this paper we propose a piezoelectric actuated seesaw (PAS) RF MEMS switch which adopts Pb(Zr, Ti)O₃ (PZT) actuators and seesaw cantilevers to meet the above requirements. The fundamental structures of PAS RF MEMS switches were designed, optimized, and fabricated. Through the developed process of PAS single pole double through (SPDT), RF MEMS switches were successfully fabricated on a 4^'' wafer and they showed good electrical properties. The driving voltage was less than 5 volts and the insertion loss was −0.5dB and the isolation was −35dB at 5GHz. The maximum switching speed was about 5kHz. Thus these RF MEMS switches can be applicable to mobile communication devices or wireless multi-media devices at a frequency lower than 6GHz.

The paper investigated performance of air bearing system in a micro device. A parametric study is carried out. The dynamic performance of a very short journal bearing (L/D < 0.1) and thrust bearing is studied. The parameters that affect the performance of the air bearing are discussed. The optimum values of the important parameters are explored, and the stability of the thrust bearing is discussed. The prototype and test result are presented.

Micro turbine is one of the important components in a micro gas turbine engine. This paper reports on the development and investigations of a micro turbine device driven by compressed air, which consists of three layers of silicon wafers and two layers of acrylic plates. The rotor has an outer diameter of 8.4 mm with a thickness of 0.76 mm. The key challenges to develop a successful high-speed turbine device are geometry design and fabrication of micro blade profiles as well as air-bearings. The micro air bearings have been designed, and a deep reactive ion etching (DRIE) process has been used for fabricating micro journal bearings with high aspect ratio. The micro turbine has reached a rotating speed of 9,000 rpm during test.

Passivating behavior of Self-assembled monolayers (SAMs) of octadecyltrichlorosilane (OTS) on an n-type Si (100) electrode has been investigated with and without a redox species like ferrocene in polar non-aqueous medium. The electron transfer behavior of ferrocene is found to be drastically affected by the presence of monolayer and reasons for this are analyzed as a function of change in resistance, dielectric thickness and coverage of the monolayer. The thickness and the coverage of the monolayer are 2.17 nm and 99.8% respectively. Further contact angle measurements illustrate the change in hydrophobicity and homogeneity of the Si substrate after derivatived with SAM.

In this paper, we presents a novel and simple method to fabricate embedded micro channels. The method based on different light absorption properties of the SU-8 thick photoresist under different incident UV wavelengths. The channel structures are defined by the ordinary I-line, while the cover layer is patterned by the deep UV. Because the deep UV is obtained directly on the same aligner with a set of filter mirrors, the embedded channel can be easily produced without other rare facilities. Besides, the relationship between the thickness of the top layer and the exposure dose of the deep UV has been measured by an ingeniously designed experiment. The specific thickness of the top layer of the embedded micro channel can then be secured by the specific deep-UV exposure dose. Further more, many meaningful mechanical structures have been realized by this method, the material property of the top layer are also measured.

A new strain-sensing structure inspired from insect's (especially the Fly) propricoception sensor is devised. The campaniform sensillum is a strain-sensing microstructure with very high sensitivity despite its small dimension (diameter ∼10 µm in a relatively stiff material of insect's exocuticle (E = ∼10⁹ Pa). Previous work shows that the high sensitivity of this structure towards strain is due to its membrane-in-recess- and strainconcentrating- hole- features. Based on this inspiration, we built similar structure using silicon micromachining technology. Then a simple characterisation setup was devised. Here, we present briefly, finite-element modeling and simulation based on this actual sample preparation for the characterisation. As comparison and also to understand mechanical features responsible for the strain-sensitivity, we performed the modeling on different mechanical structures: bulk chunk, blind-hole, thorugh-hole, surface membrane, and membrane-in-recess. The actual experimental characterisation was performed previously using optical technique to membranein- recess micromachined Si structure. The FEM simulation results confirm that the bending stress and strain are concentrated in the hole-vicinity. The membrane inside the hole acts as displacement transducer. The FEM is in conformity with previous analytical results, as well as the optical characterisation result. The end goal is to build a new type MEMS strain sensor.

Two novel mechanical coupling methods for synthesizing highly-integrated contour mode piezoelectric aluminum nitride (AlN) filters are introduced. While the underlying resonator technology remains the most viable candidate for realizing arrays of post-CMOS compatible filters at arbitrary frequencies with on-chip matching to 50 Ω, previously demonstrated mechanical coupling topologies do not scale well beyond 100 MHz. The current work focuses on design and fabrication techniques intended to extend the numerous inherent advantages of the AlN contour mode resonator technology to filters that are capable of higher center frequencies. The first design involves a series of alternating high and low acoustic impedance quarter wavelength sections that regulate the strength of the elastic coupling between resonators. The second approach relies on elastic coupling elements that are defined in the relatively compliant bottom metal electrode layer rather than the structural AlN film used by the actual resonators.

This paper presents the finite element analysis (FEA) simulation results and electrostatic characterizations of an uncooled MEMS capacitive IR detector. Thermal, thermalstructural and electrostatic-structural behaviors were simulated. The peak displacement sensitivities were calculated as 0.109nm/pW·µm⁻² and 0.029nm/pW·µm⁻² for 100µm and 50µm plates, respectively. Electrostatic-structural pull-in behaviors of the devices were tested and the results agreed with simulation well when second order mode pull-in was considered in the FEA model.

AC Electro-osmosis (ACEO) is a newly developed microfluidic mechanism, which can transport fluids and particles with low voltage that is suitable for integration with IC circuitry. We observed line formation of particles on electrodes by ACEO, leading to better understanding of ACEO microflows. Also by identifying a new ACEO mechanism from electrochemical reaction, we developed Asymmetric Polarization (A-P) ACEO technique, adding another dimension to ACEO. Both simulation and experiments have been performed to promote the understanding and optimization of ACEO devices. The experimental result of A-P ACEO is also presented in this paper.

This paper presents a self-actuating biosensor based on the piezoelectric cantilever optimized by Taguchi method for the label-free detection of specific biomoleculars. Until now, even though the optimisation of the cantilever-based biosensors have been performed by changing dimensions one by one, few researches have performed the geometric optimisation considering the overall configuration of the piezoelectric cantilever. This paper suggests a method of optimising the piezoelectric cantilever by the Taguchi method. The first resonance frequency, the separation factor, and the sensing signal of the piezoelectric cantilever were selected as the object functions. The resonator driving circuit will keep the cantilever resonance on the binding of the antigen with antibody. By real-time monitoring of the resonance frequency shift by the frequency sensing circuit, the effects of the protein binding on the change of the cantilever stiffness and mass will be investigated.

This research aims to develop capabilities in patterning micro-, nano- structures and devices using thermoplastics. Fundamental investigations are conducted using NEB-22 resist as the substrate material in the imprinting of micro- and nano- structures. Imprinting on 200 mm diameter wafers has been achieved with well acceptable uniformity. Features with linewidths down to 50 nm and uniformity with less than ±1% over an 8-inch wafer has been obtained. Micro gratings for optical sensing, nano-scaled channels and pillars for bio-related filtering have been manufactured.

We report on the development of a low cost, manufacturing process for a threedimensional network, microelectrofluidic platform. The platform consists of multiple levels of fluidic channels and electrical circuits. The inter-level channels and circuits are connected through via holes and conductor-filled via holes respectively. The medium surrounding these channels and circuits is a polymeric material, in this case, PMMA. In this research, 2 separate chips have been made: a multi-layer fluidic network and a multi-layer electrical interconnect. The future goal would be to integrate both chips into one. The process involves the hot embossing of channels on thin sheets of PMMA and the deposition of metal circuits using the conductive paste printing technique. Both processes are low cost in terms of capital investment and in terms of raw materials used to make the chips. Backend processes include multi-layer bonding, via drilling, dicing and final assembly. A 4-layer fluidic network and a 4-layer electrical interconnect based on the PMMA substrate have been fabricated through a cheap and simple process. Testing shows fluidic and electrical transmission through the multi-layer chips.

Valveless piezoelectric micropumps are in wide practical use due to their ability to conduct particles with absence of interior moving mechanical parts. In this paper, an extended numerical study on fluid flow through micropump chamber and diffuser valves is conducted to find out the optimum working conditions of micropump. In order to obtain maximum generality of the reported results, an analytical study along with a dimensional analysis is presented primarily, to investigate the main dimensionless groups of parameters affecting the micropump net flux. Consequently, the parameters appeared in the main dimensionless groups have been changed in order to understand how the pump rectification efficiency and optimum diffuser angle depend on these parameters. A set of characteristic curves are constructed which show these dependencies. The application of these curves would have far reaching implications for valveless micropumps design and selection purposes.

In electrokinetically-driven microfluidic applications, reservoirs are indispensable and have finite sizes. During operation processes, as the liquid level difference in reservoirs keeps changing as time elapses, the flow characteristics in a microchannel exhibit a combination of the electroosmotic flow and the time-dependent induced backpressure-driven flow. In this work, an assessment of the finite reservoir size effect on electroosmotic flows is presented theoretically and experimentally. A model is developed to describe the timedependent electrokinetic flow with finite reservoir size effects. The theoretical analysis shows that under certain conditions the finite reservoir size effect is significant. The important parameters that describe the effect of finite reservoir size on the flow characteristics are discussed. A new concept denoted as ''effective pumping period'' is introduced to characterize the reservoir size effect. The proposed model clearly identifies the mechanisms of the finitereservoir size effects and is further confirmed by using micro-PIV technique. The results of this study can be used for facilitating the design of microfluidic devices.

A capacitive absolute pressure sensor was fabricated using a large deflected diaphragm with a sealed vacuum cavity formed by removing handling silicon wafer and oxide layers from a SOI wafer after eutectic bonding of a silicon wafer to the SOI wafer. The deflected displacements of the diaphragm formed by the vacuum cavity in the fabricated sensor were similar to simulation results. Initial capacitance values were about 2.18pF and 3.65pF under normal atmosphere, where the thicknesses of the diaphragm used to fabricate the vacuum cavity were 20 µm and 30 µm, respectively. Also, it was confirmed that the differences of capacitance value from 1000hPa to 5hPa were about 2.57pF and 5.35pF, respectively.

We present the fabrication process and characteristics of a 3-axes flexible tactile sensor available for normal and shear mode fabricated using Si micromachining and packaging technologies. The fabrication processes for the 3 axes flexible tactile sensor were classified in the fabrication of sensor chips and their packaging on the flexible PCB. The variation rate of resistance was about 2.1%/N and 0.5%/N in applying normal and shear force, respectively. Because this tactile sensor can measure the variations of resistance of the semiconductor strain gauge for normal and shear force, it can be used to sense touch, pressure, hardness, and slip.

Wafer bonding or wafer fusion is a method of combining two same or dissimilar materials, either atomically or by means of adhesive. In this paper we report a new process to bond thin film Indium Phosphide (InP) to oxidized Silicon (100) substrates at low temperatures (>250°C). The treatment of InP epitaxial structures to oxygen plasma and the Si substrate to chemical treatment aids the substrates in contact bonding at room temperature. A thermal treatment at 220°C, completes the wafer fusion, with uniform bonding occurring along the length and breadth of the sample. The InP substrate is removed, resulting in a thin film of two micron InP bonded to oxidized Si. The InP thin film was studied for its structural and optical quality by high-resolution scanning electron microscopy, micro-PL and micro-Raman. The thin-film exhibited excellent quality and was patterned and released to form cantilever structures, showing the process capability of integrating free-standing III-V thin-films on Si platform.

This paper describes the development of a new MEMS-based optical mirror, which can perform optical switching (or scanning) function with discrete reflection angles in an outof- plane configuration. The device is fabricated through the Deep Reactive Ion Etching (DRIE) process on silicon-on-insulator (SOI) wafer, followed by wafer dicing and assembly with two metalised glass dies. The MEMS mirror can be tilted under electrostatic force between the opposite electrodes embedded on SOI and glass structures. The most outstanding feature of this MEMS mirror is the discrete and therefore, reliable tilting angles, which generated by its unique mechanical structural design and electrostatic-driven mechanism. In this paper, the concept of the new scanning mirror is presented, followed by the introduction of device design, mechanical simulation, microfabrication process, assembly solution, and some testing results. The potential applications of this new MEMS mirror include optical scanning, optical sensing (or detection), and optical switching.

A numerical model based on the total concentration of etchant is proposed to model the wet chemical etching through a circular hole. The reaction at the etchant-substrate interface is assumed to be infinitely fast i.e. etching is controlled by the diffusion of etchant to the interface. The proposed model is based on a fixed-grid approach analogous to the enthalpy method. The total concentration of etchant is the sum of the unreacted etchant concentration and the reacted etchant concentration. The reacted concentration of etchant is a measure of the etchfront position during etching. The governing mass diffusion equation based on the total concentration of etchant includes the interface condition. The etchfront position is found implicitly using the proposed approach. The computational domain is fixed, which includes the whole etchant and substrate domain including the mask region. For demonstration purposes, the finite volume method is used to solve the governing mass diffusion equation with prescribed initial and boundary conditions. The effect of mask thickness and initial etchant concentration on the shape evolution of etchfront is studied.

In recent years, highly sensitive and selective as well as cost-effective sensing and detection of biomolecules (e.g. virus, bacterial, DNA and protein) by MEMS/NEMS (Micro- /Nano Electro- Mechanical-System) structures have attracted extensive attention for its importance in clinical diagnostics, treatment, and various genome projects. Meanwhile, Substantial research efforts have been spent on the improvement of sensitivity of bioMEMS structures. Among a variety of methods that have been investigated, surface modification by nanoparticles (NPs) turns out to be an attractive way, which provides a platform for the enhancement of the sensitivity for biosensor devices. However, conventional applications for surface modification were mostly implemented on microelectrodes. Thus, in this paper, we demonstrate a new approach for surface enhancement on Au-coated silicon microcantilevers in micro-/nano-system. By self-assembly surface binding of multi-walled carbon nanotubes (MWCNTs) on the Au monolayer on top of the Si microcantilever surfaces, much larger surface area could be created for bio-molecular binding (such as antibodies or single DNA strands, which act as probes to capture target molecules). Therefore, this could enable specific interactions and selective binding to target biomolecules with a very low sample size, which greatly increases the sensitivity of detection. It should be noted that functionalization of MWCNTs with terminal carboxylic functionalities (in DCC solution) onto the Au surfaces of Si microchips have been introduced in our study. Further applications of MWCNTs functionalization are worth exploring in biomolecular detection for their exceptional mechanical and unique electronic properties. The successful binding of MWCNTs was testified as shown obviously on AFM image (Figure 1 and 2).

Micro-cantilevers are now gaining popularity in biomolecular sensing. Monitoring and mass detection of biological species can be accurately determined using the micro- or nano- scale cantilevers. The targeted biological molecules are first immobilized onto the microcantilever which is later determined through static or dynamic techniques. Optical detection method is employed to determine the deflection of the cantilever in static analysis or the shift of resonance frequency in dynamic analysis. Though both analyses using optical detection have been highly sensitive and produce accurate results, they required extensive and expensive experimental setup and are not practical for point-of-care application. Piezoresistive sensing has become an alternative approach in biological sensing as changes in mechanical properties can be converted to electrical output. This paper presents the design and simulation of a highly sensitivity piezoresistive based micro-cantilever for biomolecular detection. A series of holes are formed on the silicon based micro-cantilever. These discontinuities form the Stress Concentration Region (SCR) used to increase sensitivity for piezoresistive sensing. Finite Element Analysis (FEA) through ANSYS 8.0 was performed on the structural model to maximize the SCR so as to improve the sensitivity of the cantilever. The optimized number, geometry, radius, and the distance from the first hole to the root of these holes were discussed in this paper.

This paper presents the design and Finite Element Model (FEM) simulation of a novel electrothermal microactuators and arrays. It is a single material microactuator which deflects at its tips by differential thermal expansion of its constituent parts. The electrothermal actuator consists of three thin arms, three thin blades and two electrical connection pads. The goal of this coupled electrothermal actuator design was to multiply the force by adding the individual contributions of all the three actuators. The difference in magnitude of blade deflections depends on the geometrical characteristics of the actuators. The thermal deformation and thermal stability are easily controllable. The simulation employing ANSYS/Multiphysics software results include force, deflection, thermal stress, ideal electrothermal actuator and array geometries. The main advantage of this electrothermal actuator is large deflection of blades with very low actuation voltage in comparison with electrostatic actuators. A typical application in a micromirror is shown to illustrate the utility of these actuators and arrays.

This paper presents the overall design of an industrial vibration transmitter using Micro Electro Mechanical System (MEMS) capacitive accelerometer. It describes the accelerometer sensor interfacing circuit, rms-to-dc converter and voltage to current loop converter circuit design, calibration procedure and mounting methods. The industrial vibration transmitter output can be customized to obtain either acceleration or velocity with root mean square (rms) or peak (pk) value signal. The electronic circuit was designed to measure vibration in motion. The output of the transmitter is a current signal (4-20mA) which is proportional to input acceleration (0-10g rms). The AC coupling circuit for accelerometer sensor interfacing, RMS detector and industrial current loop converter circuit are implemented in a single printed circuit board. The prototype consists of 2 pin top connector for power input (24VDC), current output signal and stainless steel mechanical housing assembly with bottom thread connection for mounting. The loop powered acceleration vibration transmitter is employed for vibration monitoring and control applications. Keywords: Vibration transmitter, MEMS, capacitive accelerometer, AC coupling, RMS detector, current loop converter, condition monitoring.

This article investigates the motion of a cell in a carrier fluid flowing along a twodimensional channel. The cell, assumed elliptical, is modeled as a highly viscous fluid with rigid body motion. A fixed grid approach is used. A combined formulation with one set of governing equations to treat both phases is employed. The cell-fluid interface is tracked by a distance function. The finite volume method is employed to solve the governing equations. For demonstration purpose, the result for the flow of a single elliptical cell in an obstructed channel is presented.

Chemical and mechanical stability of FDTS (perfluorodecyltrichlorosilane) hydrophobic coatings was improved by using an oxide adhesion layer followed by an in-situ vapour deposition of the FDTS self-aligned monolayer. The use of silicon oxide base layer improves stability of the FDTS film and degradation of its hydrophobic properties resulting from a continuous immersion in water and other liquids. We ascribe the improved stability of the FDTS films grown on oxide to high density and uniformity of the surface hydroxyl groups required for FDTS attachment and the resulting high quality of the FDTS monolayer. This approach shows film property improvement over traditional substrates such as silicon and aluminium but may also be particularly useful in biochemistry and micro fluidics when films are deposited on substrates with lower density of the surface hydroxyl groups.

This paper attempts to prove the feasibility of a novel High Temperature Heat Flux (HTHF) sensor for gas turbine environment. Based on the latest improvement in a new type of Polymer-Derived Ceramic (PDC) material, the authors present the design and development of a HTHF sensor based on PDC material, and show that such a sensor is indeed feasible. The PDC-HTHF sensor is fabricated using newly developed polymer derived SiCN, whose conductivity is controlled by proper composition and treatment condition. Direct measurements and characterization of the relevant material properties are presented. Electrical conductivity can be varied from 0 (insulator) to 100 (ohm.cm)⁻¹; in addition a value of 4000 ppm/°C (at 600 K) is obtained for temperature coefficient of resistance. This novel sensor is found to perform quite satisfactorily at about 1400 °C for long term as compared to conventional heat flux sensors available commercially. This type of PDC-HTHF sensor can be used in harsh environments due to its high temperature resistance and resistance to oxidation. This paper also discusses lithography as a microfabrication technique to manufacture the proposed PDC-HTHF sensor. In our current design, the sensor dimensions are 2.5mm in diameter and 250 µm thickness.

This paper reports on a new decoupled micromachined gyroscope. The proposed sensor is a dual mass type, electrostatically driven to primary mode oscillation and senses, capacitively, the output signal. Full decoupling between drive and sense modes minimizes the mechanical crosstalk. Three different designs are introduced in this work. Drive and sense amplitudes, mechanical and electrical sensitivities, quality factors and approximate bandwidths are extracted analytically and the results are confirmed using finite element analysis. The first design shows drive and sense modes resonance frequencies of 4077 Hz and 4081 Hz respectively; with a frequency mismatch lower than 0.1%. The drive and sense capacitance are 0.213 pF and 0.142 pF respectively. The mechanical and electrical sensitivities are 0.011 µm/ (°/s) and 2.75 mV/ (°/s) respectively. The third design shows significantly improved mechanical and electrical sensitivities of 0.027 µm/ (°/s) and 6.85 mV/ (°/s) respectively.

This paper presents theoretical investigations of the pressure-driven two-liquid flow in microchannels with electroosmosis effect. For a fully developed, steady state, laminar flow of two liquids combined the pressure gradient and the electroosmotic effects, we have derived analytical solutions that relate the velocity profiles and flow rates to the liquid holdup, the aspect ratio of the microchannel, the viscosity ratio of the two liquids and the externally applied electric field.

Thick-film piezoelectric transducers have been produced and tested for implementation into a MEMS ultrasonic sensor array. The arrays are intended to be used for beam forming in sensing applications for fluidics in channels at millimeter or micrometer scale (e.g. flow rate measurement, detection of beads, bubbles). Stripe and matrix aligned elements have been fabricated for one-dimensional and two-dimensional beam steering, respectively. In this contribution we further concentrate on an improved Q-factor and PZT layer homogeneity as a major requirement for the transducer elements.

Emerging 3D-SiP technologies and high volume MEMS applications require high productivity mass production DRIE systems. The Alcatel DRIE product range has recently been optimised to reach the highest process and hardware production performances. A study based on sub-micron high aspect ratio structures encountered in the most stringent 3D-SiP has been carried out. The optimization of the Bosch process parameters has resulted in ultra high silicon etch rates, with unrivalled uniformity and repeatability leading to excellent process. In parallel, most recent hardware and proprietary design optimization including vacuum pumping lines, process chamber, wafer chucks, pressure control system, gas delivery are discussed. These improvements have been monitored in a mass production environment for a mobile phone application. Field data analysis shows a significant reduction of cost of ownership thanks to increased throughput and much lower running costs. These benefits are now available for all 3D-SiP and high volume MEMS applications. The typical etched patterns include tapered trenches for CMOS imagers, through silicon via holes for die stacking, well controlled profile angle for 3D high precision inertial sensors, and large exposed area features for inkjet printer heads and Silicon microphones.

Synthetic jets have been identified and utilized widely in flow control applications. The synthetic jets are usually created by a traditional PZT-driven actuator, which consists of a small cylindrical cavity that has an emitting orifice and a PZT-diaphragm or two PZTdiaphragms. A novel synthetic jet actuator is composed of two emitting slots, two sealed cavity bounded on one end by a single PZT diaphragm, and a slide block. The flow fields of the novel synthetic jet actuator in the quiescent air and the cross-flow conditions were simulated. The results show the slide block of the novel synthetic jet actuator has an important regulating function and a unique adjustable synthetic jet can be generated with slight modifications of the slide block. The adjustable synthetic jet may potentially replace the traditional synthetic jets in various applications, and also extend the applications of the synthetic jet to more flow control systems that can't be implemented by the traditional synthetic jets.

Sacrificial layer etching with different structures is studied in this work. It is found that the existed model doesn't match with the experimental data well. A modified model is proposed by considering the diffusion coefficient of HF as a function of temperature and concentration in the solution. In the modified model, the decrease of the HF concentration will cause the increase of the HF diffusion coefficient, which will partly compensate the decrease of the concentration caused by the long diffusion distance. In this way, the modified model matches with the experimental data very well both for channel structure and bubble structure. Combined structures are also studied in this work. Some interesting phenomena are observed during the etching of the combined structure, including the etching rate jumps down or up near the joint area. The proposed model can explain these phenomena well.

In the present work pull-in voltage of fixed-fixed end type MEMS switches with variative electrostatic area has been calculated using a distributed model and applying a full nonlinear finite difference discretizing method. The governing nonlinear differential equation has been derived using of the variational principle for multi domain electromechanical coupled system. The numerical results of the beam with variative electrostatic area with the results of Coupled-Domain Finite Element method have been compared and very good agreement has been achieved.

Imprint lithography has been gaining popularity as a new method to fabricate microelectro mechanical systems. The main advantages of the IL are its extremely low set-up cost, high replicating accuracy and extended fabricating critical dimension. Compare to traditional optical lithography, IL has the advantages of being able to fabricate complex pattern structure with high-aspect ratio. However, the thermal and loading errors can reduce pattern transferring fidelity. In this paper, UV curing method is used in IL process which can avoid the heat distortion of tools. Additionally, a six-step loading process for template pressing into resist film is developed. The performance of this process include: the loading locus is continuous with very high accuracy (10nm), the press releaseing control (accuracy up to 1 psi) can reduce and avoid the distortion of template structure and stage supports. This process can achieve a residual layer with thickness of 20nm and avoid the elastic stamp distorted (under 20nm) at the same time. The press force can reach up to 300 psi for 6 cm² pattern size but the friction force during demould process can be reduced to 30 psi. Experimental results reveal that it is a novel and robust process with high fidelity in micro/nano structures manufacturing.

The dry etching technology is one of the key process in the 3C-SiC MEMS fabrication. In this paper, the 3C-SiC ICP etching technology will be studied. The etching gas components we used include CHF₃, SF₆ and O₂. The polycrystal 3C-SiC films deposited on SiO₂ layer were etched in different condition. The effects of the key process parameters such as the etching gas component, the gas flow, the source power, the bias power and the etching pressure on the etch characteristics are studied detailedly. According to the results, the optimal process was obtained. Finally, we used the optimal ICP etching process to fabricate resonator successfully. The work is important and useful to fabricate the 3C-SiC MEMS devices.

There has been an increasing need for MEMS devices with composite films in recent years. This paper presents an improved model of pull-in voltage by finite-difference method (FDM) for a composite fixed-fixed beam, which takes influence of lateral residual stresses of each layer into account. Young's modulus and residual stresses of each layer for composite beam can then be extracted by these pull-in voltages. And fixed-fixed surface machined beams with multi-cup style anchor were fabricated to be suitable to the model of pull-in voltage. Validation and accuracy of the extracting method have been verified by FEM simulation and experiments.

Simulations of surface evolvement are performed using an ICP DRIE model, in which a new method is adopted for the material identification. The simulation and experimental results are shown in this paper, which indicate that the veracity provided by this modified model is satisfied. The high-efficiency of this model over other former ones are due to the ability of identification of different material by uniform algorithm, and accordingly, it has much shorter executing time. Further more, an approximate model is presented to simulate the footing effect in DRIE fabrications, with the simulation results of the surface affected by footing effect in accordance to the experiments.

We present a novel continuous electrodeless separation structure based on dielectrophoresis (DEP). The non-uniform electric field is generated by applying voltage over a circular channel. Driven by the electro-osmotic flow, the particles with different dielectric properties move continuously to the different location across the channel as they flow due to the different DEP force, thus continuously separated into the different outlets. The finite element modelling and simulation results show it can separate particles of different dielectric properties in both spatial and time domain. Compared with the previously reported dieletrophoretic separation using electrode arrays [1-10], this structure is more easily fabricated, mechanically robust and chemically inert. And compared with the previously reported electrodeless dielectrophoretic separation methods [11-14], this structure achieves higher throughput and continuous separation.

Today, semiconductor processing serves as the backbone for the bulk of micromachined devices. Precision lithography and etching technology used in the semiconductor industry are also leveraged by alternate techniques like electroforming and molding. The nature of such processing is complex, limited and expensive for any manufacturing foundry. This paper details the technology elements developed to manufacture cost effective and versatile microfluidic devices for applications ranging from medical diagnostics to characterization of bioassays. Two applications using multilayer ceramic technology to manufacture complex 3D microfluidic devices are discussed.

An improved model of the contact resistance in a MEMS DC-contact switch is presented and the sticking effect is included. In this model, the JKR theory is used to determine the sizes of contact spots and the electrical contact theory is used to estimate the contact resistance. The relationship between the contact resistance and the applied force has been investigated in different cases for a common Au-Au contact. The results suggest that the contact resistance is related to the applied force, the number of asperities, and the surface energies of contact materials. However, the height distribution of asperities has little influence on the contact resistance. The comparison between the improved model and the measurements that have been reported suggests the sticking contact model is more reasonable than the elastic contact model especially at low applied forces.

The theory, design, and fabrication of a novel structure for measuring power of microwave signals are presented. The novelty of this sensor is that it measures the microwave power with which is coupled from the CPW line by the MEMS membrane. In this method the signal is available during the power detection. The simulation and process of this sensor are given.

This paper presents a new micro-rotating structure for the local measurement of residual strain in thin films. Compared with a conventional rotating structure, the new structure doesn't have a rotating point, but has lower residual strain distribution after deformation, a more precise test model, and larger measurement range. An analytical expression to calculate the residual strain is given so that the residual strain can be easily evaluated from the deflection of the rotating beam. Finite-element method (FEM) was also used both to optimize the design and to calibrate the new structure. Residual strains in LPCVD polysilicon films were determined by the new structure and compared with measurements by the conventional rotating structure. The two methods lead to comparable results.

This paper introduces a novel method for the simulation and verification of the laterally-driven electrothermal microactuator. A nodal analysis model of the electrothermal microactuator was built without meshing. This model may simulate the static and dynamic behaviour of the electrothermal microactuators with variational thermal conductivity, electrical resistivity and thermal expansion coefficient. There are only three stages of ODEs in the model, but its static relative error is below 5% in comparison with the results of the nonlinear model of ANSYS with the nonlinear geometrical options turned on. The equivalent circuit was then built to present the capability of co-simulating with the control and feedback circuits.

A thermopnuematic peristaltic micropump for controlling micro litters of fluid was designed and fabricated from multi-stack PDMS structure on glass substrate. Pump structure consists of inlet and outlet, microchannel, three thermopneumatic actuation chambers, and three heaters. In microchannel, fluid is controlled and pumped by peristaltic motion of actuation diaphragm. Actuation diaphragm can bend up and down by exploiting air expansion that is induced by increasing heater temperature. The micropump characteristics were measured as a function of applied voltage and frequency. The flow rate was determined by periodically recording the motion of fluid at Nanoport output and computing flow volume from height difference between consecutive records. From the experiment, an optimum flow rate of 0.82 µl/min is obtained under 14 V three-phase input voltages at 0.033 Hz operating frequency.

Results from both experimental and numerical studies have already shown the significant package effects on the performance and the reliability of MEMS devices. To enable the theoretical predictions of these packaging effects, a compact joint model of an entire packaged MEMS device is established based on the Cell Library Concept and the Nodal Analysis Method. This modeling methodology greatly simplifies the package-device co-design work compared with the conventional numerical ways, and its precision is guaranteed due to its clarity in the physical nature.

While deep reactive ion etching (DRIE) has proven to be a boon for silicon micromachining applications, certain factors still exist which affect the satisfactory performance of DRIE. Some of the process limitations include bottom grass formation, RIE lag, loading and notching effects and aspect ratio dependent etching. This paper presents the effect of SF₆ flow rate and etching/passivation cycle time on the etched shape profile and bottom grass formation. Rectangular trenches of varying widths are etched using Alcatel etching system. Critical DRIE process parameters, such as SF₆ flow rate and ratio of etching and passivation cycle time, are varied to explore the dependence of etched shape profile on these parameters. It is found that low SF₆ flow rate, i.e. 250 sccm, results in relatively smooth bottom surface. As SF₆ flow rate is increased, bottom surface roughness increases and grass forms on the bottom of etched trenches. Shape of etched surface profile was found to be changed from positive profile to negative profile, when the SF₆ flow rate was increased. Ratio of etching/passivation cycle was also found to be critical for prevention of bottom grass formation. DRIE process parameters were optimised to get smooth and vertical sidewalls.

A dynamic behavior analysis of a compliant four-bar micromechanism is explored in this work. The Pseudo-Rigid-Body Model (PRBM) is used to model the compliant mechanism, and to analyze the large deflection of flexible segment. This model and Lagrange Equations are used to develop the dynamic equations. An example is given with all required parameters of a mechanism. The PRBM is also modelled in ADAMS, and the lagrangian model results are compared to the results obtained from ADAMS. Finally, a commercial finite element code capable of nonlinear analysis is used to model the mechanism with its flexible segment. By this way a comparison of PRB model and real model is proposed.

Recently AC electroosmosis has attracted research interests worldwide. This paper is the first to investigate particle line assembly/patterning by AC electroosmosis. Since AC electroosmotic force has no dependence on particle sizes, this technique is particularly useful for manipulating nanoscale substance, and hopefully constructs functional nanoscale devices. Two types of ACEO devices, in the configurations of planar interdigitated electrodes and parallel plate electrodes, and a biased ACEO technique are studied, which provides added flexibility in particle manipulation and line assembly. The paper also investigates the effects of electrical field distributions on generating microflows for particle assembly. The results are corroborated experimentally.

This work presents the modeling and analysis of CMUT using the MEMS simulation software, Coventorware. A rectangular membrane CMUT of area 40µm X 20µm with 0.2µm thickness of silicon nitride as the movable membrane was designed. To reduce the parasitic capacitance, silicon substrate with gold was used as the fixed bottom electrode, and the combination of aluminium and chromium were used as top electrode. The simulations were performed using Finite Element Modeling techniques. The various parameters greatly affecting the performance of CMUT such as resonant frequency, which decides the proper operation of CMUT as a transmitter or receiver and collapse voltage, the maximum voltage which the device can withstand are analyzed. It was also observed that the resonant frequency of the device decreases as the applied bias voltage increases. The changes were found due to the interesting effect known as electrostatic spring softening.

Modeling and simulation of MEMS devices are used to optimize the design, to improve the performance of the device, to reduce time to market, to minimize development time and cost by avoiding unnecessary design cycles and foundry runs. The major design objectives in any device design, is to meet the required functional parameters and the reliability of the device. The functional parameters depend on the geometry of the structure, material properties and process parameters. All model parameters act as input to optimize the functional parameters. The major difficulty the designer faces is the dimensions and properties used in the simulation of the MEMS devices can not be exactly followed during fabrication. In order to overcome this problem, the designer must test the device in simulation for bound of parameters involved in it. The paper demonstrates the use of interval methods to assess the electromechanical behaviour of micro electromechanical systems (MEMS) under the presence of manufacturing and process uncertainties. Interval method guides the design of pullin voltage analysis of fixed-fixed beam to achieve a robust and reliable design in a most efficient way. The methods are implemented numerically using Coventorware and analytically using Intlab.

In this paper, a complete nonlinear finite element model for coupled-domain MEMS devices with electrostatic actuation and squeeze film effect is developed. For this purpose, a corotational finite element formulation for the dynamic analysis of planer Euler beams is employed. In this method, the internal nodal forces due to deformation and intrinsic residual stresses, the inertial nodal forces, and the damping effect of squeezed air film are systematically derived by consistent linearization of the fully geometrically nonlinear beam theory using d'Alamber and virtual work principles. An incremental-iterative method based on the Newmark direct integration procedure and the Newton-Raphson algorithm is used to solve the nonlinear dynamic equilibrium equations. Numerical examples are presented and compared with experimental findings which indicate properly good agreement.

Thermal buckling behavior of line shape microactuators in a fully coupled field process is simulated. As a consequence of the miniaturizing, some effects belong to coupling of different physical fields appear, and some issues, which are minor at macroscopic scales, have to be taken into account. In order to have a robust design of these micro-systems, it is important to correctly analyze the coupling between electrical, thermal and mechanical fields. Rregarding effect of more physical aspects and ignoring the simplifying statements, the calculated results are consistent more with reported experimental measurements in the literature. recommended modifications not only improve the results to be consistent with experiments, but also play key roles for the development of MEMS actuators based on jouleheating effects such as Heactuators and Hexsil tweezers. While the simulation of micro actuators mostly consist of coupled field analyses, the results proves the requirement of transferring more detailed outputs from one field to another one as inputs.

Many Lab-on-Chip applications require sample pre-treatment systems. Using electric fields to perform cell lysis in bio-MEMS systems has provided a powerful tool which can be integrated into Lab-on-a- Chip platforms. The major design considerations for electro-lysis devices include optimal geometry and placement of micro-electrodes, cell concentration, flow rates, optimal electric field (e.g. pulsed DC vs. AC), etc. To avoid electrolysis of the flowing solution at the exposed electrode surfaces, magnitudes and the applied voltages and duration of the DC pulse, or the AC frequency of the AC, have to be optimized for a given configuration. Using simulation tools for calculation of electric fields has proved very useful, for exploring alternative configurations and operating conditions for achieving electro cell-lysis. To alleviate the problem associated with low electric fields within the microfluidics channel and the high voltage demand on the contact electrode strips, two ''control plates'' are added to the microfluidics configuration. The principle of placing the two controlling plate-electrodes is based on the electric fields generated by a combined insulator/dielectric (glass/water) media. Surface charges are established at the insulator/dielectric interface. This paper discusses the effects of this interface charge on the modification of the electric field of the flowing liquid/cell solution.

We examine various microfluidic channel designs for sample delivery to silicon nano-wire biosensors pertaining to the modeling and simulation. Nano-wires with its high sensitivity permits label free detection of bio-molecules. Without careful considerations to its fluidic delivery network, effects of detection can be limited. Different micro-channel designs of relatively larger width aid in fluid release and sensors are placed strategically to attain high efficiency in bio-sample delivery. One design establishes the viability of hydrodynamic focusing through splitting a single flow into two and permits focusing of bio-samples at the flow recombination region. It avoids the delicated fluidic delivery systems generally used in hydrodynamic focusing. A focusing effect of 71.3% based on the movement of a massless particle in the fluid is achieved using a straight channel design with a partition wall inside. Moreover, sample is focused in low velocity region which maintains minimal impact to nanowire sensor. This provides a simple and efficient delivery system for the nano-wire sensor upon integration.

The reattachment of separated air flows can be actively controlled by blowing oscillatory air jets in the boundary layer, through submillimetric holes situated near the separation edge. To achieve such pulsed jets, a high flow rate, high actuation frequency microvalve was designed, fabricated and characterized. The microvalve is fed by a pressurized source of air, and its inner channel is alternatively pinched by a PDMS polymer membrane, modulating the air flow which is addressed towards the separated surface. Magnetostatic actuation was chosen for its high stress, high displacement, and remote actuation capabilities. The actuation consists in coupling an inductive driving coil and a NdFeB permanent magnet situated on the PDMS flexible membrane. Characterization of the resonance frequency, and vibration amplitude are achieved by interferometric means. The output flow is characterized using strioscopy visualization and hot wire anemometry methods. The design and fabrication process of the microsystem, and the results of these characterizations are presented in this paper.

One motivating application of this technology is the development of a tactile display interface, where discrete mechanical actuators apply vibratory excitation at discrete locations on the skin. Specifically, this paper describes the development fabrication and characterization of a 4 x 4 micro-actuator array of vibrating pixels for fingertip tactile communication. The vibrting pixels are generated by using an electromagnetic microresonator. The fabrication sequence and the actuation performance of the array are also presented.

In this paper, we present the simulation results of a new MEMS micro-hotplate design for gas sensor applications. The structure is designed to be fabricated on a glass substrate by the low cost process including physical vapor deposition, photolithography, electroplating, and photoresist-sacrificed process. The electro-thermo-mechanical behaviors of the proposed structure have been simulated by CoventorWareTM. In the simulation, the effects of thickness of the NiCr heater layer temperature, mechanical deflection, stress, and power consumption are evaluated. The 3D simulation on results show that the temperature, displacement, stress and current density are pronounced at the center of the beam as desired. At the nominal sensor temperature of ∼400 °C, the power consumption and Mises stress are greatly reduced from 126 to 7 mW and 1280 to 472 MPa as the thickness decreases from 5 to 0.25 µm. In contrast, the compressive beam deflection is not monotonically increased as thickness increases and it is maximum at the thickness of ∼0.5 µm. Therefore, the simulation results indicate that the proposed design with 0.25 m-thick NiCr heater requires very low power consumption of 7 mW with low stress suitable and acceptable membrane deflection for gas sensor applications.

This study is about how to lower the driving voltage that enables to move the micro droplet by the EWOD (Electro Wetting On Dielectric) mechanism. EWOD is well known that it is used µ -TAS digital micro fluidics system. As voltages are applied to the device which is fabricated with dielectric layer between electrode and micro droplet, the hydrophobic surface is changed into the hydrophilic surface by its electrical property. EWOD induces the movement of micro droplet with reducing contact angle of micro droplet. Because the driving voltage depends on the dielectric constant of dielectric layer, it can be reduced by increase of dielectric constant. Typically, driving voltage of these devices was 30V∼100V and Teflon film was coated to provide hydrophobic surface. This high voltage induces many problems. In previous study, we used Ta₂O₅ as the dielectric layer and driving voltage was 23V that reduced 24 percent compared with SiO₂. In this study, we used BZN (Bi₂O₃-ZnO-Nb₂O₅) layer which had high dielectric constant. It operated the just on 12V. And micro droplet was moved within 1s on 14V. It reduced the voltage until 35 percents compared with Ta₂O₅ and 50 percents compared with SiO₂. The movement of micro droplet within 1s was achieved with BZN (ferroelectrics) just on 14V. Teflon film which is coated to provide hydrophobic surface is a very difficult to control accurate concentration, and unnecessary processes which uses metal as a protect layer in patterning should be added. So instead of Teflon coating, surface was treated to hydrophobic with R.F. atmospheric plasma.

Control of surface properties in microfluidics systems is an indispensable prerequisite for the success of bioanalytical applications. Poly(dimethylsiloxane) (PDMS) microfluidic devices are hampered from unwanted adsorption of biomolecules and the lack of methods to control electroosmotic flow(EOF). Among the various methods of hydrophilic treatment, a new cleaner technology was chosen to treat PDMS. By using atmospheric RF plasma, hydrophilic surfaces can be created. Thus, analysis was conducted with AFM, XPS, and contact angle before and after plasma treatment. Constructing hydrophilic surfaces without changing the true character of that surface has previously been costly and time consuming. But by using atmospheric plasma cost and time are both greatly reduced. There are many other benefits of hydrophilic surface treatment, including the capability to increase adhesion and capillary effects, etc. Also, with hydrophilic treatment of the micro channels on the PDMS surface, surface tension is reduced thus allowing fluids to move easily along those channels. However, the most important aim is to increase the capillary effects without any deposition or chemical treatment.

There are several application areas where the simultaneous measurement of rates of rotation about three mutually orthogonal axes is required. In this paper the principle features of a 3-axis vibrating ring gyroscope are described. The fabrication process for the gyroscope is presented and employs standard MEMS techniques. The modal properties for the ring are measured experimentally using laser vibrometry and electrostatic sensing and compared with the design predictions. In operation as a rate gyroscope it is necessary to excite the primary motion of the gyroscope and control is amplitude. As Q-factors of vibratory gyroscope are typically of the order 10³-10⁴ slight variations in environmental conditions will perturb the natural frequency of the primary mode significantly. To ensure the primary motion of the gyroscope is maintained with constant amplitude a control scheme employing both frequency tracking and amplitude control is required. An electronic control system using digital signal processing (DSP) has been developed to ensure excitation of the primary motion occurs at resonance with controlled amplitude. The control scheme employs an embedded processor to generate the drive frequency (via a D/A converter) and to monitor the primary vibration (via an A/D converter). Experimental results from the control scheme highlighting its effectiveness over conventional PLL approaches are presented.

A contribution to reliability studies of Solidly Mounted Resonators (SMR) submitted to harsh environments such as temperature and humidity is presented. Electrical, structural and chemical monitoring of representative parameters is performed by means of RF, DC characterizations and also X-ray diffraction coupled to X-fluorescence to assess aging in microstructures. Results indicate that humidity affects samples stronger than high temperature. From viewpoint of robustness, non-negligible effects of SiO₂ mass-loading on antiresonance and resonance frequencies are reported. Drifts of parameters for a lonely resonator and filter transmission are both in good accordance. Finally, the need of a full sheet passivation layer is demonstrated in order to protect metals and Aluminum Nitride (AlN) against oxidation and pollutant compounds respectively.

A 3-D simulator named SEAES has been presented for silicon anisotropic etching process simulation based on a novel 3-D continuous cellular automata (CA) model. The boundary conditions are greatly simplified in the top-most layer and high index planes such as <311> plane can be efficiently incorporated into the novel 3-D continuous CA model. The simulator is friendly and convenient for various users. The anisotropic etching can be efficiently simulated for different conditions such as etchant temperature, etchant concentration and substrate doping concentration, and the simulation results by SEAES are in good agreement with the experimental results.

A novel integrated spatial filtering detector chip was introduced in this paper through the comparison with the conventional spatial filtering detectors. We designed and fabricated a novel integrated spatial filtering detector chip with variable multi-valued weighting function using CMOS 0.35µm process. This chip has 7-bit signed weight values and a weighting control circuit though the external interface with the PC. The multiplication of the frequencies is available from the dividing the weighting function of the chip. In order to con.rm the validity of this chip, a simple velocity measurement was achieved. Experimental results show multiplied frequency ratio regarding to the reference frequency which are in proportion to the velocity of the measuring object.

This paper investigates the design constraints and possibilities given when designing a micromechanical band pass filter for intermediate frequencies (e.g. 10 MHz). The class of filters are based on coupled clamped-clamped beams constituting an H-shaped structure. A primary beam can electrostatically be activated in one of its different harmonic modes, setting the filter center frequency. The motion is transferred to an accompanying beam of equal dimensions by a mechanical coupling beam. The placement or coupling points of the quarterwavelength coupling beam which connects the vertically resonating beams is critical with respect to the bandwidth of the filters. Of special concern has been to investigate realistic dimensions allowing the filters to be processed by an actual foundry process and to find out how the choice of materials and actual dimensions would affect the performance.

In order to make a robust design of microsystems, it is important to analyze the electrical, thermal and mechanical fields including the actual input parameters. These microdevices, which typically are made of brittle materials such as polysilicon, show wide scatter (stochastic behavior) in properties as well as substantial uncertainty in the shape and geometry because of manufacturing processes. These behaviors necessitate either costly and time-consuming trial-and-error designs or, more efficiently, the development of a probabilistic design methodology for MEMS. Computer aided MEMS simulations regarding performance, power consumption, and reliability is an important design task due to high prototyping costs. Since microbeams have a wide range of applications in MEMS actuation mechanisms, analysis of the thermomechanical behavior of these actuators is very important. In the present work, assessing meaningful uncertainties involved in thermally driven microbeams, the stochastic finite element model (SFEM) is developed and implemented. The analysis shows a large deviation in buckling temperature and thermal stresses for reasonable probability density functions of characteristic parameters. Although computationally significantly more expensive than deterministic electromechanical simulation, the work illustrates the requirement of stochastic modeling for true estimation of microsystems' performance.

In this paper we present two different techniques for automated extraction of system models from FEA models. We discuss two different algorithms: for (i) automated N-DOF SME for electrostatically actuated MEMS and (ii) automated N-DOF SME for MEMS inertial sensors. We will present case studies for the two different algorithms presented.

This paper describes the concept of Electrohydrodynamic (EHD) pumping in microchannels and the study of EHD pumps in IntelliSuite's Microfluidic simulation module. The EHD pump study focuses on the factors influencing the velocity of fluid flow such as the conductivity of the fluid, the frequency of the driving AC voltage, the phase of the driving signal, the dimensions of the electrode, the gap between the electrodes and the number of driving electrodes. The results from the simulation will be used to characterize the presented design of the EHD pump. The presented design for the study of the EHD pump has a microchannel with a length of 0.2mm, width of 0.08mm and a thickness of 0.08mm. The width of the driving electrodes present at the bottom of the channel is 0.01mm and the gap between the electrodes is 0.04mm.

Recent years have witnessed many developments in microfluidic and micro-total analysis systems (µTAS) by applying microfabrication technology to biological and chemical processing. The paper reports an alternating current electro-osmotic (ACEO) particle trap for use in lab-on-a-chip. It is the first to demonstrate an integrated particle trap on cantilevers. It is expected that with the use of pre-concentrator (particle trap), the sensitivity of real-time detection can reach into sub-parts-per-trillion range. Also multiplexing detection can be achieved by coating cantilevers with various sensitive layers.

This paper describes the modeling and simulation of ''Multi Port RF Switch'' where the latching mechanism is realized with two hot arm electro thermal actuators and the switching action is realized with electrostatic actuators. It can act as single pole single thrown as well as single pole multi thrown switch. The proposed structure is modeled analytically and required parameters are simulated using MATLAB. The analytical simulation results are validated using Finite Element Analysis of the same in the COVENTORWARE software.

Design methodology of MEMS device for reducing the product development time and cost have been proposed in this paper. Design process starts with development of mathematical models and validation of the models by the finite element analysis using the CoventorWare software. Device dimension optimisation was done using the evolutionary optimisation techniques.

Over the last few years interests have emerged for application of MEMS in telecommunications. The use of MEMS for optical switching has turned to be the most attractive since this application could revolutionize fiber optic telecommunications. In this paper a robust control strategy based on sliding-mode control theory is developed for a MEMS optical switch, considering electrical, mechanical, and optical models. Sliding-mode control enables compact realization of a robust controller tolerant of device characteristics variation, non-linearties, and types of inherent instabilities. Robustness of proposed control scheme against disturbances is proved by Lyapunov second method and demonstrated through simulations. In addition, the presented control scheme is simple to implement in practical application.

A 3-dimensional mesofluidic separator has been successfully designed and fabricated using a low-temperature co-fired-ceramic (LTCC) technology. This mesofluidic separator consists of several vertical micro-channels and horizontal distribution cavities to create the velocity increase before entering a bent microchannel. The centrifugal force created by the bent microchannel further increases the fluid velocity to enhance the plasma skimming effect. Separation of the white and red blood cells in anti-coagulated blood has been demonstrated using this mesofluidic separator.

In this paper, we report the design, fabrication and characterization of an In Silico cell physiology biochip for measuring Ca²⁺ ion concentrations and currents around single cells. This device has been designed around specific science objectives of measuring real time multidimensional calcium flux patterns around sixteen Ceratopteris richardii fern spores in microgravity flight experiments and ground studies. The sixteen microfluidic cell holding pores are 150 by 150 µm each and have 4 Ag/AgCl electrodes leading into them. An SU-8 structural layer is used for insulation and packaging purposes. The In Silico cell physiology lab is wire bonded on to a custom PCB for easy interface with a state of the art data acquisition system. The electrodes are coated with a Ca²⁺ ion selective membrane based on ETH-5234 ionophore and operated against an Ag/AgCl reference electrode. Initial characterization results have shown Nernst slopes of 30mv/decade that were stable over a number of measurement cycles. While this work is focused on technology to enable basic research on the Ceratopteris richardii spores, we anticipate that this type of cell physiology lab-on-a-chip will be broadly applied in biomedical and pharmacological research by making minor modifications to the electrode material and the measurement technique. Future applications include detection of glucose, hormones such as plant auxin, as well as multiple analyte detection on the same chip.

Cell migration on two-dimensional (2-D) surface is distinctively different from cell migration in threedimensional (3-D) matrix. Although cell motility on 2-D matrix is widely studied, 3-D cell migration is just beginning to be understood. With the development of micro-fluidic systems, it is possible to study cell motility under much better controlled conditions. In this work, we present techniques for controlled coating of 3-D extracellular matrix (ECM) within microfluidic devices. This coating technique relies on the dominance of capillary forces and surface tensions in micro systems. We have successfully created uniform coating of Matrigel across microgaps of different lengths. This simple and reproducible method will have widespread biological applications such as the study of 3-D cell migration, the coating of basement membrane for cancer metastasis and angiogenesis study.

Physics-based modeling provides a powerful tool for investigating the biomechanics of soft tissue deformation incorporated with knowledge of mechanical properties using appropriate boundary conditions. We have developed a physics-based atlas model with detailed anatomical information based on Cerefy Brain Atlas. A nonlinear hyper-viscoelastic mechanical property typically suited for neurosurgery simulation has been incorporated. This model accounts well for brain tissue deformation during neurosurgical procedures (strain rate between 0.001s-1 - 1.0s-1). It is able to simulate the deformation for the entire brain and individual sub-cortical structures as well. The limiting stress relaxation for an infinitesimally small loading has also been obtained (shear modulus reaching 194.62 Pa) exhibiting similarity with a hydrocephalic condition.

Among various MEMS sensors, a rate gyroscope is one of the most complex sensors from the design point of view. The gyro normally consists of a proof mass suspended by an elaborate assembly of beams that allow the system to vibrate in two transverse modes. The structure is normally analysed and designed using commercial FEM packages such as ANSYS or MEMS specific commercial tools such as Coventor or Intellisuite. In either case, the complexity in analysis rises manyfolds when one considers the etch hole topography and the associated .uid flow calculation for damping. In most cases, the FEM analysis becomes prohibitive and one resorts to equivalent electrical circuit simulations using tools like SABER in Coventor. Here, we present a simpli.ed lumped parameter model of the tuning fork gyro and show how easily it can be implemented using a generic tool like SIMULINK. The results obtained are compared with those obtained from more elaborate and intense simulations in Coventor. The comparison shows that lumped parameter SIMULINK model gives equally good results with fractional e.ort in modelling and computation. Next, the performance of a symmetric and decoupled vibratory gyroscope structure is also evaluated using this approach and a few modifications are made in this design to enhance the sensitivity of the device.

This paper presents a new method of depositing low stress silicon nitride (SiN_x) with high deposition rate using a plasma-enhanced chemical vapour deposition (PECVD) system (STS, Multiplex Pro-CVD). By increasing the operating power of the PECVD system at the high frequency mode (13.56MHz), the deposition rate also increases while that the level of intrinsic stress within the SiN_x film decreases. The relationships between some of the key deposition parameters of the experiment such as chamber pressure, silane (SiH₄), ammonia (NH₃) and nitrogen (N₂) flow rates and the two important response variables namely the level of intrinsic stress and deposition rate are established within this investigation.

A new structure for a passive telemetry LC absolute pressure and temperature sensor is proposed, analytically simulated, and optimized to be used in a Tire Pressure Monitoring System (TPMS). This device is designed to measure a range of pressure from 0 to 100psi with an average sensitivity of 194.8KHz/psi and a wide temperature range of −100°C to more than +300°C with a sensitivity of 0.273Ω/°C. The die size measures 6mm*6mm and the maximum working frequency is 56MHz.

The present work proposes an adhesive bonding technique, at wafer level, using SU-8 negative photoresist as intermediate layer. The adhesive was selective imprint on one of the bonding surface. The main applications are in microfluidic area where a low temperature bonding is required. The method consists of three major steps. First the adhesive layer is deposited on one of the bonding surface by contact imprinting from a dummy wafer where the SU-8 photoresist was initially spun, or from a Teflon cylinder. Second, the wafers to be bonded are placed in contact and aligned. In the last step, the bonding process is performed at temperatures between 100°C and 200°C, a pressure of 1000 N in vacuum on a classical wafer bonding system. The results indicate a low stress value induced by the bonding technique. In the same time the process presents a high yield: 95-100%. The technique was successfully tested in the fabrication process of a dielectrophoretic device.

In the novel prototype of micro gyroscope structure, the new configured capacitance sensing scheme for the micro gyroscope is analyzed and the virtual instrument based detection scheme is implemented. The digital lock-in amplifier is employed in the capacitance detection to restrain the noise interference. The capacitance analysis shows that 1000aF capacitance variation corresponds to 0.1 degree of the turn angle. The differential capacitance bridge and the charge integral amplifier are used as the front signal input interface. In the implementation of digital lock-in amplifier, a new routine which warranted the exactly matching of the reference phase to signal phase was proposed. The result of the experiment shows that digital lock-in amplifier can greatly eliminate the noise in the output signal. The linearity of the turn angle output is 2.3% and the minimum resolution of turn angle is 0.04 degree. The application of the digital lock-in amplifier in the field of micro-electro-mechanical-system (MEMS) device signal detection is a new attempt, and it shows the prospective for a high-performance application.

A variable RF capacitor with a-Si:H (doped with phosphine) cantilevers as the top electrode were designed and fabricated. Because the top multi-cantilever electrodes have different lengths, increasing the applied voltage pulled down the cantilever beams sequentially, thus realizing a gradual increase of the capacitance with the applied voltage. A high-k material, H_fO₂, was used as an insulating layer to increase the tuning range of the capacitance. The measured capacitance from the fabricated capacitor was much lower and the pull-in voltage was much higher than those from theoretical analysis because of incomplete contact of the two electrodes, existence of film differential stresses and charge injection effect. Increase of sweeping voltage rate could significantly shift the pull-in voltage to higher values due to the charge injection mechanisms.

To reduce power consumption and operation temperature for micro-thermal actuators, metal-based micro-mechanical locks with multi-locking positions were analyzed and fabricated. The micro-locks consist of two or three U-shaped thermal actuators. The devices were made by a single mask process using electroplated Ni as the active material. Tests showed that the metal based thermal actuators deliver a maximum displacement of ∼20µm at a much lower temperature than that of Si-based actuators. However Ni-actuators showed a severe back bending, which increases with increasing applied power. The temperature to initiate the back bending is as low as ∼240°C. Back bending increases the distance between the two actuators, and leads to locking function failure. For practical application, Ni-based thermal actuators must be operated below 200°C.

Micro-batteries are one of the key components that restrict the application of autonomous Microsystems. However little efforts were made to solve the problem. We have proposed a new planar zinc/air micro-battery, suitable for autonomous microsystem applications. The micro-battery has a layered structure of zinc electrode/alkaline electrolyte/air cathode. A 3D zinc electrode with a high density of posts was designed to obtain a high porosity, hence to offer a best performance. A model of the micro-battery is developed and the device performances were simulated and discussed. A four-mask process was developed to fabricate the prototype micro-batteries. The preliminary testing results showed the micro-batteries is able to deliver a maximum power up to 5 mW, and with an average power of 100 µW at a steady period for up to 2hrs. Fabrication process is still under optimization for further improvement.

The most important aspect of biosensor development with high sensitivity is the oriented immobilization of antibodies on the solid substrate. Human IgG was immobilized on gold-coated silicon employing protein A, protein G and neutravidin immobilization procedures. The amount of human IgG immobilized was analyzed by 3, 3^', 4, 4^'- tetramethyl benzidine (TMB) substrate assay and was maximum when protein A immobilization procedure was followed. Human IgG coated biosensing surface was regenerated by treatment with glycine-HCl buffer (50 mM, pH 2.2). Atomic force microscopy was used to analyze the distribution of biomolecules immobilized on gold-coated silicon. Our study indicates that human IgG molecules were uniformly bound to gold-coated silicon by protein A immobilization procedure.

In this paper, depositing of low stress Amorphous Silicon (α-Si) with high deposition rate by using a plasma-enhanced chemical vapour deposition (PECVD) system (STS, Multiplex Pro-CVD) was studied. The influence of the process parameters, such as power, frequency mode, argon flow rate, temperature and pressure, on these objectives have been studied and optimized. RF modes (13.56 MHz and 380 kHz) have obvious influence on the deposition rate of amorphous silicon, which revealed that high RF mode provide higher deposition rate, but not certain on the residue stress. The power has a proportional relationship to the deposition rate, and also, is proportional to stress induced at high RF mode, so low power is preferred for low stress film. At high RF mode, the deposition rate decreases with temperature while stress increases. By increasing the gas flow rate of argon, the film stress is found to decrease for both RF modes, while the deposition rate decreases for the low RF mode. Lastly, at high RF mode, pressure is also proportional to deposition rate and stress (compressive). The proper process conditions were optimized to get the low stress α-Si. The application of -α-Si sacrificial layer in the glass etching process is also briefly highlighted and illustrated at the end of this paper.

We start by presenting a short explanation of the micro actuator working principle. The main contribution of this paper is the characterization of the coefficient of stiction between two silicon nitride parts of a MEMS actuator. Having one flat contact surface while the other is composed of many relatively sharp circular bumps, has the advantage that the effective contact area is drastically reduced. The stiction coefficient varies between 0-0.53 for the device configuration presented. The exact value depends closely on the electrostatically applied force which presses the textured part on to the smooth one. Individual measurements used are highly accurate (typically within 5 nm noise band) and identical measurements for the characterization of stiction show only a small variation, typically under 25nm on a range of 11.8µm.

Having nanosize and unique electrical properties, carbon nanotubes (CNTs) attract lot of interest among scientific community all over the world. One of the recent observations is its role as nanosensors. Obviously the nanosize and high strength of CNT are most preferred parameter for technical and electromechanical field in the industrial point of view. The defects in CNT structure have a vital role in determining their electrical and mechanical properties. Our earlier study indicates an effective role played by the topological defects like pentagon and octagon on the electromechanical properties of these nanostructures. Here our aim is to look in to the effect of Stone-wales defect and chirality on this property of nanotubes deformed under applied pressure. Among the three kinds of tubes considered for this study, we observed that armchair (5, 5) tube is more suitable for sensor applications.

Electric double layer (EDL) effect has been proven to have significant effect in microchannel. However most of models were based on 2-D flow, the first analysis on EDL effect on 3-D flow field was reported by Tan and Ng. In this paper, one of 3-D effects, which are the aspect ratio on the microchannel with EDL, will be shown and discussed. Parameters such as friction coefficient, fRe and Nusselt Number, Nu were used to determine the performance microchannel. Nernst and Plank model was used here to model the EDL effect. It is found that in decreasing of aspect ratio, the values of fRe increase. It is also concluded that the decrease in aspect ratio is resulted with an increase in the Nu values.

In this paper we investigate the effects of dimensional and material stiffness variations on a microrelay performance. A linear displacement bistable micromechanism is modelled by pseudo-rigid-body model method and fully characterized. To find the effects of dimensional and material stiffness variation, an analysis of mechanical error is used. The method is a stochastic one and takes into account the random nature of variations. Variations of the contact force and required power of a microrelay example is obtained by the method introduced and the performance of the microrelay is determined. The method introduced is a simple, effective and general that may be used at the design level.

The formation of hinge-like portions typically is encountered in the structural topological synthesis. This paper proposes an optimum synthesis integrated with the analytic single-axis flexure hinge as a second-stage design process to obtain optimum flexure configuration and location for promoting the overall performance of a compliant microgripper after the topology optimization. The locations of hinge-like in topology synthesis are verified to be the exact locations of flexures. A simplifying optimization applying ANSYS is consequently done in the second-stage optimum design. The proposed process can be extended to other types of compliant structural design.

The advent of silicon micromachining has opened up numerous opportunities for the commercialization of many miniaturized sensors. Coupled with matured silicon technology, one of the beneficiaries is the capacitive micromachined microphone, a simple yet very elegant microsensor. For earlier MEMS microphones, because of the constraints of surface micromachining, a thin layer of air is enclosed within an etched cavity between a diaphragm and a backplate. Bulk micromachining, coupled with wafer bonding and DRIE (Deep Reactive Ion Etching), provides another attractive avenue of fabricating better performance and robust MEMS microphones. As a result, a more accurate and reliable modeling approach is required to reflect the shift in fabrication techniques. The theory of a condenser microphone is reviewed. With reference to a B & K MEMS microphone, the theoretical results are compared, which demonstrate good agreements with those reported experimental ones. In addition, the positive effect of an acoustic slot around the circumference of a backplate is also demonstrated.

Microfluidic is a field of considerable interest. While significant research has been carried out to develop microfluidic components, very little has been done to integrate the components into a complete working system. We present a flexible modular system platform that addresses the requirements of a complete microfluidic system. A microfluidic stack system is demonstrated with the layers of the stack being modular for specific functions. The stack and accompanying infrastructure provides an attractive platform for users to transition their design concepts into a working microfluidic system quickly with very little effort. The concept is demonstrated by using the system to carry out a chemilumiscence experiment. Details regarding the fabrication, assembly and experimental methods are presented.

We fabricated a Si stencil X-ray mask only in a dry process without electroplating and chemical etching. An X-ray absorber of thickness 30 µm with vertical sidewalls was able to be fabricated. In addition, we succeeded in demonstration of the X-ray lithography in the beam line BL-4 of the synchrotron radiation facility TERAS of AIST. Line and space patterns of line width 2 - 200 µm were transcribed plainly on the surface of a PMMA sheet. It was confirmed that the edge of PMMA microstructures was sharp. There is a possibility that this Si stencil mask can be applied as an X-ray mask for the deep X-ray lithography.

Beijing Synchrotron Radiation Facility (BSRF ) is a partly dedicated synchrotron radiation ( SR) source operated in either parasitic or dedicated mode. LIGA research at BSRF started from 1993 and focused in the first two steps of deep X-ray lithography and electroplating. Scanning exposure chamber of deep X-ray lithography was first built in 1996 on a 3W1 wiggler beamline with very hard X-ray and high X-ray density. We used the system for the research of LIGA deep X-ray lithography for many years, and found that the wiggler beamline does not meet the LIGA deep X-ray lithography for its disadvantages of small and bad uniform X-ray spot of 30mm on the wafer in horizontal and the very high X-ray power density on the wafer which causes the distortion of resist structures by the large heat load on the resist. In 2001 we used a bending magnet beamline (3B1) as deep X-ray lithography instead of wiggler beamline. The 3B1 beamline is divided to be 3B1B as LIGA deep X-ray lithography and 3B1A as nano X-ray lithography. The electroplating is used to make the mechanical parts and mold insert with nickel and copper materials for different applications.

The LIGA process, which combines deep X-ray lithography with electroforming and polymer molding, is a main fabrication method for producing MEMS. And hot embossing is one of the main processing techniques for polymer microfabrication, which helps the LIGA (UV-LIGA) technology to achieve low cost mass production. And electroforming of LIGA mold insert with lower surface energy and friction coefficient is required for demolding process during hot embossing to obtain better polymer replicas. In this paper, the Ni-PTFE compound material mold inserts is fabricated by special treated galvanic bath and operation conditions. And the results show that it is a robust Ni-PTFE composite micro-electroforming and basically changes the interaction property when demolding for producing high quality polymer replicas.

Design and fabrication of microfluidic devices on polymethylmethacrylate (PMMA) substrates for electrochemical analysis applications using improved UV-LIGA process are described. The micro-channel structures are transferred from Nickel mould into the plastic plates by hot embossing method. During the mould fabrication, the exposure process is optimized for the large ratio of exposed area to unexposed area of negative photo-resist (SU-8), then non-planar electroforming technique is used for the large line space of the SU8 photoresist mold. Microelectrodes for electrochemical detection are fabricated on other blank PMMA plates through lift-off process. Then these substrates with microchannels are bonded to PMMA plates with microelectrodes by thermal bonding method based on surface modification. In this study, the PMMA microchips of capillary electrophoresis for electrochemical detection (CE-ECD Chips) have been demonstrated by electrophoretic separation of L-ascorbic and uric acid. The results indicate that the fabrication of CE chips by this improved UV-LIGA process has potential of mass production with low cost.

There has been a large demand for the realization of on-chip fluxgate magnetic sensors, with exciting and sensing control IC circuits. Based on UV lithography and other MEMS technology, a new three dimensional solenoid type micro magnetic sensor has been designed and fabricated to measure the components of magnetic induction vector in outer space. The fabricated micro sensor was integrated in IC circuits of MEMS satellite.

This paper addresses the 2D and 3D micro- and nanofabrication of ElectroMagnetic MetaMaterials (EM³) for the terahertz range. EM³ refers to artifbial composite materials which consist of a collection of repeated metal elements designed to have a strong response to applied electromagnetic felds, so that near resonance both the effective permittivity and magnetic permeability µ become simultaneously negative. This unusual situation leads to exotic consequences such as a negative index of refraction and an inverse Doppler and Cerenkov effect. EM³ fabricated so far have been mostly two-dimensional and in this respect are highly anisotropic. By anisotropic, it is inferred that the response of the system depends on the direction of illumination. The anisotropic nature of the metamaterials impedes eventual real-life applications of the negative media as it places constraints on the impinging electromagnetic waves. Ways of producing three-dimensional (3D) or more isotropic EM³ by means of tilted x-ray exposures will be introduced. Basic geometry tells us that if the structures are inclined at 30-45°, this would lead to an improvement of the coupling of the vector by 50-70%

SSLS (Singapore Synchrotron Light Source) has set up a complete one-stop shop for micro/nanofabrication in the framework of the LIGA process. It is dubbed LiMiNT for Lithography for Micro and Nanotechnology and allows complete prototyping using the integral cycle of the LIGA process for producing micro/nanostructures from mask design/fabrication over X-ray lithography to electroplating in Ni, Cu, or Au, and, finally, hot embossing in a wide variety of plastics as one of the capabilities to cover a wide range of application fields and to go into higher volume production. The process chain also includes plasma cleaning and sputtering as well as substrate preparation processes including metal buffer layers, plating bases, and spin coating, polishing, and dicing. Furthermore, metrology using scanning electron microscopy (SEM), optical profilometry, and optical microscopy is available. LiMiNT is run as a research lab as well as a foundry. In this paper, several industrial applications will be presented, in which LiMiNT functions as a foundry to provide external customers the micro/nano fabrication services. These services include the fabrication of optical or X-ray masks, of micro/nano structures from polymers or from metals and of moulds for hot embossing or injection moulding.

We report on fabrication of nanoimprint stamps for fabrication of two dimensional photonic crystals in visible range of spectra. Nanoimprint stamps made of silicon and/or nickel were successfully fabricated using electron beam lithography and advanced dry etching techniques. The quality of the stamps was evaluated using scanning electron microscopy. The fabricated stamps were also evaluated by imprinting them into suitable polymer materials.

X-ray lithography is an established technique for the micro fabrication of MEMS and MOEMS well known for low sidewall surface roughness, submicron critical dimension, and high aspect ratio. Recently the typical characteristics of this technique has been developed approaching new opportunities deriving by the possibility to perform tilted exposure and by the combined use with electron beam lithography that allow to shape with direct patterning already the final material in 3D micro and nanostructures. The general approach is to concentrate the complexity of the multi layer fabrication process required to obtain 3D nanostructures mostly on the lithographic process. This capability represent a micro- and nanofabrication tool enabling new technologies. In this paper will be shown a multiple-tilted X-ray lithography procedure combined with e-beam lithography to create sub-micrometric patterns of arbitrary shape buried in 3D structure. The use of deep x-ray lithography in multi exposure configuration has been also exploited for the production of biodegradable 3D scaffold structures and of micro needles based transdermal delivery tools fabrication.

Since 1995 CAMD has been offering exposure services, so called print shop for a variety of users interested in making precision High-Aspect-Ratio Microstructures (HARMST) for various application. Services have been expanded beyond only the print shop service in recent years and now include x-ray mask fabrication, substrate preparation for PMMA and SU- 8 resists, electroplating, finishing and molding. Metallic and polymeric parts are now routinely fabricated for precision engineering, micro-fluidic and micro-optic applications. This paper presents a brief overview of the actual status of LiGA services provided at CAMD including ongoing research efforts and examples of LiGA components for different applications.

A three-step technique for MEMS quality optimization is presented. It exploits the relative merits of its constituent optimization components. Analog Devices accelerometer was the test device with microstructure dimensions serving as design parameters [6]. Manufacturing design rules [7] and sensor performance requirements served as design constraints. A static model relating input acceleration to sensed voltage was used, neglecting sensor and signal conditioning dynamics. The trimming yield of the ADXL50[6], with sensitivity as the design target, was improved by 37%. We show that the three-step method enables the search for an optimal design in a semi-automatic manner by facilitating user interaction. Our final goal is to enable the generation of MEMS mask layout while ensuring robust designs with minimum sensitivity to fabrication process variations

Joule heating is resulted from inevitable volumetric heating when an electric field is applied across conducting media and it would impose limitations to the performance of electrokinetic microfluidic devices. In this paper, the Joule heating and its effects on electroosmotic flow (EOF) in PDMS microfluidic channels are reported. 3D numerical simulation of the Joule heating induced temperature field and its effects on the EOF and electrophoretic transport of solutes in microchannels was performed. Experiments were carried out to verify the proposed models and the developed numerical code. A Rhodamine B based thermometry technique was used to measure the solution temperature distributions in PDMS microfluidic channels. The micro particle image velocimetry (micro-PIV) technique was used to characterize the velocity profiles of the EOF under the influence of Joule heating. The numerical simulations were compared with the experimental results, and reasonable agreement is found. Both the numerical simulations and the experimental results show that the presence of the Joule heating causes the EOF velocity to deviate from its normal ''plug-like'' profile; the EOF velocity exhibits a concaved shape in the hydrodynamically developing region and a convex (parabolic) pattern in the fully developed region.

In this paper, the radial and tangential electric field forces are given. Based on the electromechanical coupled dynamic equations of the drive system, by generalized force and generalized coordinate, the forced response of the drive system to torque fluctuation are investigated. Changes of the forced response along with the system parameters are given as well. The micro flexible ring radius and clearance between the micro ring and stator, etc. have obvious influences on the forced responses of the drive system. These results are useful in design and manufacture of the micro drive system and can offer some reference for other micro electromechanical systems.

This paper presents the advantages of spray coating technique as compared to the conventional spin coating method for photoresist coating of 3D microstructures. An optimized mix of photoresist AZ4620: MEK: PGMEA (1:1.5:0.5) was used to achieve good coverage and uniformity of photoresist not only on planar surface, but also along the trenches' sidewall. In order to achieve the ideal coverage of photoresist layer, the effects of the geometries of the microstructures were also considered. Then, we implement this technique for our application in a MEMS device to prove the viability and potentiality of spray coating of photoresist for fabrication of 3D microstructures.

In this paper, the development of wafer bonding techniques of the most frequently used materials Si-to-glass, glass-to-glass and Si-to-Si is reported. To improve the bond quality of Si-to-glass and make glass-to-glass bonding viable at bonding temperatures less than 300 °C, a hydrogen-free amorphous silicon layer of 20-100 nm thickness is deposited as an intermediate layer. For Si-to-glass bonding, without applying the amorphous film, both the bond efficiency and bond strength are low. With the assistance of the amorphous film, the bond quality is significantly improved and the bonding temperature is reduced. Glass-to-glass bonding has also been successfully achieved at low temperatures, the high bond quality is still maintained. For Si-to-Si bonding, a tempered sol-gel film is deposited on Si wafer surface. The results show that promising Si-to-Si can be realized at bonding temperatures less than 300 °C . It is also suitable to III-V semiconductor compounds bonding. Based on the bonding techniques obtained above, any combination of Si, III-V semiconductor compounds and glass wafers can be bonded and integrated. The bonding techniques can be widely used for various microsystems packaging at low temperatures.

Silicon ultrasonic transducer micro arrays based on micro-electro-mechanicalsystem (MEMS) technologies are gaining popularity for applications in sonar sensing and excitation [1]. A current challenge for many researchers is modelling the dynamic performance of these and other micro-mechanical devices to ascertain their performance and explain experimental observations reported [2]. In this work, the performance simulation of a MEMS ultrasonic transducer array made from silicon nitride has been successfully carried out using CoventorWare package. The dynamic response of the entire transducer array was characterised, and the results were compared with theoretical predictions. Individual elements were found to vibrate with Bessel-like displacement patterns, and they were resonant at approximately 3 MHz, depending on thickness and lateral dimensions [3]. The frequency shows a linear dependence around the common thickness of 2 µm. Peak displacement levels were examined as a function of frequency, DC bias voltage, and AC drive voltage. Accounting for fabrication variations, and uniformity variations across the wafer, the full array showed minimal variations in peak out-of-plane displacement levels across the device, and isolated elements that were over-responsive and under-responsive. Presently, the effect of observed variations across the array on the performance of the transducers and their radiated fields are being examined.

Silicon pressure sensors based on micro-electro-mechanical-systems (MEMS) technologies are gaining popularity for applications in bio-medical devices. In this study, a silicon piezo-resistive pressure sensor die is used in a feasibility study of developing a manometric catheter for functional swallowing disorders diagnosis. The function of a manometric catheter is to measure the peak and intrabolus pressures along the esophageal segment during the swallowing action. Previous manometric catheters used the water perfusion technique to measure the pressure changes. This type of catheter is reusable, large in size and the pressure reading is recorded by an external transducer. Current manometric catheters use a solid state pressure sensor on the catheter itself to measure the pressure changes. This type of catheter reduces the discomfort to the patient but it is reusable and is very expensive. We carried out several studies and experiments on the MEMS-based pressure sensor die, and the results show the MEMS-based pressure sensors have a good stability and a good linearity output response, together with the advantage of low excitation biasing voltage and extremely small size. The MEMS-based sensor is the best device to use in the new generation of manometric catheters. The concept of the new MEMS-based manometric catheter consists of a pressure sensing sensor, supporting ring, the catheter tube and a data connector. Laboratory testing shows that the new calibrated catheter is capable of measuring pressure in the range from 0 to 100mmHg and maintaining stable condition on the zero baseline setting when no pressure is applied. In-vivo tests are carried out to compare the new MEMS based catheter with the current version of catheters used in the hospital.

The variation of effective parameters in Micro Electro Mechanical Systems strongly affects their performance, design, and control. Hence, it is essential to understand and model the effective parameters in MEMS devices to optimize their designs. Typical MEMS (Microresonator) employ a parallel-plate capacitor, in which one plate is actuated electrically and its motion is detected by capacitive changes. In this paper we investigate nonlinear modelling of microresonators. The nonlinearities from capacitor (quadratic) and midplane stretch were considered for this purpose. The achieved microbeam's equations are nondimensionalized and by using the multiple scales method received to the equations which identified the relations between system dynamics and effective parameters of system. In other part of this paper we expand the Fuzzy Generalized Cell Mapping (FGCM) for multiparameter systems then apply FGCM to the microresonator and see how the uncertainties can affect the working domain of dynamical systems. It can be seen FGCM is so useful method for detecting the working region with variation of parameters.

This paper presents a novel concept for transport of aqueous sample in capillaries. The concept is based on the thermocapillary effect, which utilizes the temperature dependency of surface tension to drive a sample droplet. To date, the major problem of this concept was the evaporation of the aqueous sample. In our approach, a liquid-liquid system was used for delivering the sample. The aqueous sample is protected by silicone oil, thus evaporation can be avoided. A transient temperature field drives both liquids away from a heater. The paper first presents a theoretical model for the coupled thermocapillary problem. Next, the paper compares and discusses experimental results with different capillary sizes. The results show the huge potential of this concept for handling sample droplets dispersed in oil, which are often created by droplet-based microfluidics.

This paper presents a new low temperature silicon-glass anodic bonding process using induction heating. Anodic bonding between silicon and glass (Pyrex 7740) has been achieved at temperature below 300 °C and almost bubble-free interfaces have been obtained. A 1KW 400KHz power supply is used to induce heat in graphite susceptors (simultaneously as the high-voltage electrodes of anodic bonding), which conduct heat to the bonding pair and permanently join the pair in 5 minutes. The results of pull tests indicate a bonding strength of above 5.0MPa for induction heating, which is greater than the strength for resistive heating at the same temperature. The fracture mainly occurs across the interface or inside the glass other than in the interface when the bonding temperature is over 200 °C Finally, the interfaces are examined and analyzed by scanning electron microscopy (SEM) and the bonding mechanisms are discussed.

Minimally invasive surgery (MIS) is the most exciting and rapidly developing area where force sensing is actually of central importance. Micromachined piezoelectric sensors can be integrated onto MIS tools for improved diagnosis and treatment monitoring. A micro-machined freestanding lead zirconate titanate (PZT) force sensor is fabricated using five masks process incorporating deep reactive ion, ion beam and wet-chemical etching techniques. The PZT sensor is designed as a parallel plate capacitor structure in which the sol-gel prepared 1-µm thick PZT film is sandwiched between top (Au/Cr) and bottom (Pt/Ti) metal electrodes mounted on a thin Si membrane. This paper also describes a new wet chemical approach for patterning PbZr_0.52Ti_0.48O₃ films. The etch recipe provided excellent etch control, minimized undercut, preserved the photoresist mask, and effectively removed the residues on the etched surfaces. A high etch rate (200 nm/min), high selectivity with respect to photoresist, and limited under-cutting (1.5:1, lateral : thickness) were obtained. The fabricated force sensor exhibited good ferroelectric properties. The current fabrication procedure and electrical analysis can be considered as a breakthrough for fabricating freestanding PZT force sensor in any desired shape and dimensions, as well as a good example of ferroelectric microdevices.

During the design and simulation process of MEMS medical devices used in neurosurgery, there is a need to build a brain model with detailed anatomy and physical properties incorporated as a platform to conduct numerical analysis. This paper presents a study on constructing a brain model for simulation of medical device interventions during neurosurgery. A brain atlas was utilized to develop a detailed model consisting of multiple structures. Two types of atlas model were generated employing different mesh types and biomechanical properties suited for various applications. The developed model was able to capture the detailed anatomy of the brain and reflect the application-dependant biomechanical behaviour based on material modelling of brain tissue under surgical intervention.

With the rapid development of micro-electro-mechanical system (MEMS) technology, uncooled micromechanical infrared detectors become available and attract more and more attention. This paper first deducts the theory of bilayer cantilever with different stress in each layer, and then applies it to the design of micromechanical photon detectors. This theory is somewhat different from the theory in many literatures because it is based on not surface stress but layer stress. With this theory, optimized design of micromechanical photon detectors can be performed, which includes both material choice and geometry determination. As an example, a high sensitivity silicon-based micromechanical photon detector is designed, which reaches a sensitivity of 47 times larger than conventional designs.

A novel pressure sensor based on the Fabry-Perot interferometry and microelectromechanical system (MEMS) technology is proposed and demonstrated. Light is coupled into the sensor through a fiber. Dual-wavelength demodulation method is used to analyze the reflected optical signals and compensate the errors independent of optical wavelength. Theoretical analysis and simulation results are presented. Experimental results for pressure measurements ranging from 0 Mpa to 3 Mpa demonstrate reasonable linearity and sensitivity.

A microaccelerometer with highly reliable, wafer-level packaged MEMS sensing element and fully differential, continuous time, low noise, BiCMOS interface circuit is fabricated. The MEMS sensing element is fabricated on a (111)-oriented SOI wafer by using the SBM (Sacrificial/Bulk Micromachining) process. To protect the silicon structure of the sensing element and enhance the reliability, a wafer level hermetic packaging process is performed by using a silicon-glass anodic bonding process. The interface circuit is fabricated using 0.8 µm BiCMOS process. The capacitance change of the MEMS sensing element is amplified by the continuous-time, fully-differential transconductance input amplifier. A chopper-stabilization architecture is adopted to reduce low-frequency noise including 1/f noise. The fabricated microaccelerometer has the total noise equivalent acceleration of 0.89 µg/√Hz, the bias instability of 490 µg, the input range of ±10 g, and the output nonlinearity of ±0.5 %FSO.

This paper presents a microfluidic system for manipulation and separation of micron-sized particles based on the combined use of negative dielectrophoresis (DEP) and hydrodynamic forces. A 3-D microelectrode structure (so called paired electrode array) are constructed face to face on the top and bottom sides of the microchannel and driven with highfrequency AC voltage to generate dielectrophoretic gates. Depending on the relative strengths of the two forces, particles such as polystyrene beads or cells carrying by a laminar flow can either penetrate the gate or settle there. This gives rise to certain applications including selectively concentrating particles from the flow, separating particles depending on their sizes or dielectric properties, and automatically positioning particles to selective locations. For this purpose, a microfluidic device consisting of the paired electrode array sitting on the channel has been fabricated using microfabrication techniques. Polystyrene beads were used to study the performance of the device. Experimental results including the concentration and separation of particles are presented.

This paper reports a continuous-time capacitance to voltage converter (CVC), based on the charge integration circuit, for capacitive pressure sensor applications. Unlike conventional charge integrators which need a large feedback resistor for biasing, the proposed method uses low duty cycle periodic reset to establish a robust dc bias at the sensing electrode. The CVC has the merits of low noise, linear transfer characteristics and low susceptibility to system offset. A CVC has been designed with standard 0.35µm CMOS technology. For a 3.3-V supply, it achieves 1mW power consumption, 0∼0.8pF detection range and 0.06% resolution.

A simulation model of vibratory capacitive microgyroscope and its driving loop is designed using SPICE. The vibratory microgyroscope is basically microelectromechanical system; therefore the simulation model should be expressed mechanical and electrical properties. To modelling the microgyroscope, the Analog Behavioral Model is used. In order to design a driving loop of vibratory microgyrosope, the the Barkhausen criteria is considered. The co-simulation of MEMS sensing element and its interface circuit is performed. The SPICE simulation model of the vibratory microgyrocope is designed, and the driving loop of the microgyroscope is simulated using the designed simulation model. The simulation results demonstrate the validity of the designed model and its interface circuit

Several sorts of MEMS (Microelectromechanical Systems) based have been demonstrated by using electrostatic actuation scheme up to date. The comb drive and parallel plate are the two most common electrostatic actuators that have been well studied in variable optical attenuator (VOA) applications. In addition to the known retro-reflection type of optical attenuation being realized by our new devices driven by electrothermal actuators in present study, a novel planar tilted mirror with rotational and translation moving capability is proposed by using electrothermal actuators as well. Using electrothermal actuators to provide said planar tilted mirror with rotational and translational displacement has granted us a more efficient way to perform the light attenuation for in-plane structure. The static and transient characteristics of devices operated at ambient room temperature environment show good repeatability and stability.

We present the design, fabrication and characterization of a novel microvalve realized by combining micro and fine machining techniques. The design is for high flow rates at high pressure difference between inlet and outlet, burst pressure of up to 15 bars, there is no power consumption required for the valve to maintain its position during operation in any intermediate state and the process gas does not interact with the actuation mechanism. The microvalve was experimentally characterized with airflows. It is shown that flow rates of 220 ml/min at a pressure difference of 4 bars could be achieved with the minimum accurate flow rate of 2-8 ml/min.

Using the network etch rate function model, the anisotropic etch rate of p-type single crystal silicon was characterised in terms of microscopic properties including step velocity, step and terrace roughening. The anisotropic etch rate data needed have been obtained using a combination of 2 wagon wheel patterns on different substrate and 1 offset trench pattern. Using this procedure the influence of an applied potential has been investigated in terms of microscopic properties. Model parameter trends show a good correlation with chemical/electrochemical reaction mechanism and mono- and dihydride terminated steps reactivity difference. Results also indicate a minimum in (111) terrace roughening which results in a peak in anisotropic ratio at the non-OCP applied potential of −1250 mV vs OCP.

This paper proposes design concept and fundamentals of a novel acceleration microswitch (G-switch), which is an integration of bimorph actuator and field effect transistor (FET). This micro-switch can be used to actuate the alarm system for call for helps - minimizing injuries after the fall among elderly; or trigger the air-inflatable hip protector for the fall prevention. The device can be attached to the developed MEMS-Wear smart shirt. Its structural design and switching FET are optimized using the global optimization method so that the bimorph as a movable gate can collapse on the gate insulating layer, when there is an impact force, which is greater than a threshold value (experimentally found to be 4.8g based on the previously published report). This contactless mechanism optimizes the field effect between the bimorph and the substrate causing an electrical current flow profusely with a sensitivity of 0.1 mA/V² with a FET's ratio of ∼19. The device will consume less power as the gate to source voltage (V_GS) can be applied up to 4 V. All design parameters must satisfy the specified design constraints. In future, the optimized design will be fabricated and incorporated into the smart shirt for testing upon the fall events.

This paper presents a behavioural modelling technique for micromechanical beam resonators that enables the simulation of MEMS resonator model in Analog Hardware Description Language (AHDL) format within a system-level circuit simulation. A 1.13 MHz clamped-clamped beam and a 10.4 MHz free-free beam resonators have been modelled into Verilog-A code and successfully simulated with Spectre in Cadence. Analysis has shown that both models behave well and their electrical characteristics are in agreement with the theory.

This paper studied the detection of falls and activities of daily living (ADL) with two objectives: (1) minimum number of sensors for a broad range of activities and (2) maximize the comfort of the wearer for long term use. We used a garment to provide long term comfort for the wearer, with a 3-axis MEMS accelerometer on the shoulder position, as a wearable platform. ADL were detected in time-frequency domain and summation of absolute peak values of 3-D acceleration signals was used as feature in fall detection. 6 male and female subjects performed approximately five-hour long experiment. Sensitivity of 94.98% and specificity of 98.83% for altogether 1495 activities were achieved. Our garment-based detection system fulfilled the objective of providing the comfort of the wearer in long term monitoring of falls and ADL with high sensitivity. In fall detection, our device can summon medical assistances via SMS (Short Message Service). This detection system can raise fall alarm (fall SMS) automatically to individuals to get a shortened interval of the arrival of assistance.

This paper presents a method of using a body-distributed smart sensor platform for continuous detection of vital physiological signs in a body area network (BAN) system. An overview of the approach utilising predefined sentinel vital sign events is mentioned in order to optimise the platform in both hardware and software level. A BAN system consisting of smart sensor platform with short range ISM transmission will be used to communicate with a communication gateway. This communication gateway will encode and send the signals via Bluetooth to designated devices to inform caregivers, family members or transmit information to internet server.

A novel Single Deeply Corrugated Diaphragm (SDCD) based dual optical fiber Fabry-Perot pressure sensor for blood pressure measurement is proposed. Both mechanical and optical simulations are performed to demonstrate the feasibility and superior performance of the proposed sensor. Result shows that less than 2% nonlinearity can be achieved for the proposed sensor using optimal Fabry-Perot microcavity. Also, the fabrication process of the proposed sensor is given, instead of complicated fusion bonding process, only bulk and surface micromachining techniques are required which facilitate the mass production of such biocompatible and disposable pressure sensors.

This paper presents a method of using smart sensors for continuous detection of vital physiological and physical gait signals that can be relayed to a fall prediction algorithm for predicting an imminent faint fall. A novel MEMS based BP sensor will be discussed briefly. Once an imminent faint fall is detected, fall prevention and injury minimization devices will be activated. A body area network consisting sensor circuits utilizing short range ISM communication will be used to enable signal transmission to a processor which acts as a communication gateway as well. This processor would then encode and send the signals via Bluetooth to designated devices to effect inform caregivers or family members.

Design and fabrication of a miniature combination lock is reported. The prototype's outline size is less than 15mm × 20mm × 25mm, with the function of 24 steps single-try discrimination. Two miniature application-specific electromagnetic motors are used to drive a counter meshing gears (CMG) mechanism. Ratchet-pawl mechanism is respectively attached to each CMG gears assembly, to insure it step forward at accurate angles in company with motor driving circuit. Main functional components of the lock are fabricated by UV-LIGA micromachining process, including the motor's stator with 4-level planar coils. Handcraft assembling process and control circuit design are also briefly introduced. The prototype had already endured more than 1000 times of unlocking and 100 times of manually unlocking. It is proved that micro-motor and micromachining technologies are very useful in miniaturization of such a surety device.

Recent developments in electron beam equipment have given rise to ever more complex electron optical (EO) designs. Until now these designs were realized using standard workshop techniques like drilling, turning etc. With the need for even more complex designs to advance electron optics, we use the possibilities of manufacturing EO components with MEMS fabrication techniques. This leads to different design rules in the EO design. One can use one of the strong points of MEMS fabrication, mass manufacturing of identical and reliable components within tight specifications. One of our designs that demonstrates this is presented in this paper, the multi-beam electron source. We are developing an electron source for use in a standard scanning electron microscope that produces 100 beams instead of one. The design is made so that the performance in terms of spot size and current per beam is equal to the performance of the beam from a single beam source, around 1 nm and 25 pA. Furthermore, since we modify the SEM for nanolithography purposes, it is necessary to switch each of the individual beams on and off. For that purpose we integrate an array of blanker electrodes in the source unit.

In this paper a Signal Processing Module (SPM) for the computer-aided analysis of heart sounds has been developed. The module reveals important information of cardiovascular disorders and can assist general physician to come up with more accurate and reliable diagnosis at early stages. It can overcome the deficiency of expert doctors in rural as well as urban clinics and hospitals. The module has five main blocks: Data Acquisition & Pre-processing, Segmentation, Feature Extraction, Murmur Detection and Murmur Classification. The heart sounds are first acquired using an electronic stethoscope which has the capability of transferring these signals to the near by workstation using wireless media. Then the signals are segmented into individual cycles as well as individual components using the spectral analysis of heart without using any reference signal like ECG. Then the features are extracted from the individual components using Spectrogram and are used as an input to a MLP (Multiple Layer Perceptron) Neural Network that is trained to detect the presence of heart murmurs. Once the murmur is detected they are classified into seven classes depending on their timing within the cardiac cycle using Smoothed Pseudo Wigner-Ville distribution. The module has been tested with real heart sounds from 40 patients and has proved to be quite efficient and robust while dealing with a large variety of pathological conditions.

The present work presents a microfluidic device with interdigitated microelectrode and microchannel for fetal nucleated red blood cell dielectrophoresis properties characterization using crossover frequency method. To obtain the electric field and its gradient along the microchannel, simulation study was done by using MAXWELL™ software. Results show maximum electric field and gradient are obtained near the electrode edge and they are affected by electrode width and the electrode gap. The crossover frequency should be obtained by keeping the cell moving near the electrode edge. The device has been successfully used in fetal cell characterization with better than 1KHz frequency repeatability, which is about 2% of the measured crossover frequency.

A microdevice using AC electrokinetic flow and negative dielectrophoresis for cell delivery is proposed, designed and fabricated. The device is made from an unequal width interdigitated microelectrode located at the bottom of microchannels, with AC voltage applied to the small and large electrode. Negative dielectrophoresis is used to prevent the cells from sinking down to the bottom of delivery channel. The flow rate is affected by the electrode pair dimensions, applied frequency and voltage and are analysed. The device electrode width is from 4µm to 20µm and it is microfabricated on glass wafer using gold thin film. 3 microchannels connected to 2 reservoirs are covered by the electrode pair for the delivery channel. SU-8 micromold is used for the channels' PDMS fabrication.

The electromechanical behaviour of cantilever beam MEM switches incorporating linear residual stress gradient is studied in this work. Using Finite-difference method (FDM), behavioural models that predict the electrostatic deflection and pull-in voltage of such structures have been established. The model accounts for the effect of residual stress gradient on the mechanical behaviour of the cantilever MEM switches, and results have been validated via comparison with experimental data. The completed model offers an efficient means of design, analysis and optimization of cantilever-based electrostatically actuated MEMS devices. It can also be utilized for material property measurement and analysis.

The pull-in phenomenon of nanotube electromechanical switches as a fixed-fixed carbon nanotube suspended over a graphitic ground electrode is investigated. This model captures the geometric nonlinearity and stretching of nanotube caused by large deflection, and nonlinearity of electrostatic pressure with correction. The effects of radius and length of nanotube and the influence of initial gap is examined. The results calculated by full nonlinear Finite Difference method were compared with the results of Energy method and good agreement achieved.

This paper presents developed processes for silicon microneedle arrays microfabrication. Three types of microneedles structures were achieved by isotropic etching in inductively coupled plasma (ICP) using SF₆/O₂ gases, combination of isotropic etching with deep etching, and wet etching, respectively. A microneedle array with biodegradable porous tips was further developed based on the fabricated microneedles.

This paper presents a developed process for fabrication of hollow silicon microneedle arrays. The inner hollow hole and the fluidic reservoir are fabricated in deep reactive ion etching. The profile of outside needles is achieved by the developed fabrication process, which combined isotropic etching and anisotropic etching with inductively coupled plasma (ICP) etcher. Using the combination of SF₆/O₂ isotropic etching chemistry and Bosch process, the high aspect ratio 3D and high density microneedle arrays are fabricated. The generated needle external geometry can be controlled by etching variables in the isotropic and anisotropic cases.

This work investigates the isotropic etching properties in inductively coupled plasma (ICP) etcher for microneedle arrays fabrication. The effects of process variables including powers, gas and pressure on needle structure generation are characterized by factorial design of experiment (DOE). The experimental responses of vertical etching depth, lateral etching length, ratio of vertical etching depth to lateral etching length and photoresist etching rate are reported. The relevance of the etching variables is also presented. The obtained etching behaviours for microneedle structure generation will be applied to develop recipes to fabricate microneedles in designed dimensions.

Here we report a BioMEMS based microfluidic device as a deformation assay to study the deformability and growth capability of cells through microgaps. The micro-gaps are ranging from 3µm to 30µm with three microchannels parallel to each other to mimic the blood vessel bio-microenvironment. Flow conditions in the device can be controlled to have an environment as similar to that in vivo as possible. We used osteoblast cells with approximate size of 30 µm as a model cell to study the deformation ability of this cell to migrate through the 3 µm gap. Such a device enabled us, for the first time to measure the cell deformation with ease. More importantly, we are able to observe the cellular responses to gaps present in the device and understand the mechanics behind the morphological change of the cells.