Journal of Micromechanics and Microengineering

The integration and parallelization of nanopore sensors are essential for improving the throughput of nanopore measurements. Solid-state nanopores traditionally have been used in isolation, which prevents the realization of their full potential in applications. In this study, we present the microfluidic integration of an array of 30 solid-state nanopores, which, to our knowledge, is the highest number reported to date. Our microfluidic network was fabricated using high-resolution epoxy photoresists, and the solid-state membranes were bonded through a dry process using complementary surface chemistries. We successfully measured integrated nanopores using external electrodes. This paper discusses the limitations of our methods, particularly concerning microfluidic interfacing and scaling to higher channel counts. Additionally, we present theoretical analysis of current blockades and noise in integrated nanopores, predicting that maintaining low series resistance between the nanopore and electrode is crucial for resolving short events.

Drug-induced cardiac toxicity is a critical concern in drug development, often leading to unreliable results and potential drug withdrawal due to the lack of mature cardiomyocytes in screening assays. This study aimed to enhance cardiomyocyte maturation by combining structural and conductive stimuli, specifically using a Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) coated conductive PDMS membrane and a mechanical stimulation (MS) system. A 10% tensile strain at a frequency of 1 Hz was applied via a stepper motor controlled by an Arduino-based system, with real-time monitoring through an integrated strain sensor. The highly stretchable PEDOT:PSS strain sensor was incorporated into the well-placed surface to ensure precise MS. The functional well plate, featuring PEDOT:PSS-coated conductive microgrooves, was designed to align cardiomyocytes and promote the expression of maturation markers, including α-actinin and connexin43 (Cx43). Results showed that the combination of 10% mechanical strain and a conductive PEDOT:PSS surface significantly increased sarcomere length and Cx43 intensity compared to controls. This approach provides a more physiologically relevant environment for cardiomyocyte development, offering a more accurate model for assessing drug-induced cardiotoxicity in preclinical drug screening.

With the continuous advancement of technology, flexible electronic devices are gradually becoming integrated into our daily lives. These devices exhibit remarkable properties such as flexibility, bending capability, and resilience. One challenge in the development of these devices is to achieve a balance between transparency and conductivity for flexible transparent stretchable electrodes. In this article, a stretchable, transparent and self-powered multifunctional sensor, specifically a stretchable triboelectric nanogenerator (STENG sensor), is fabricated. It is consisting of a friction layer made of a micro-structured polydimethylsiloxane film, and high stretchable electrodes fabricated by spin-coated silver nanowire (AgNW) on thermoplastic polyurethane (TPU) film. The TPU/AgNW electrode exhibits a high transparency (85.26%) and conductivity (7.04 Ω sq⁻¹) after three spin-coating processes. The STENG sensor has high transparency, high pressure sensitivity (0.014 99 V kPa⁻¹) and fast response (20 ms). The sensing performance decreases by only 24% when the deformation reaches 100%.

To compensate for the growing need for flexibility in pressure-sensing wearable devices, solid–liquid mixed-phase sensors have been improved to meet application needs. Compared to their all-solid-state counterparts, these sensors exhibit improvements in flexibility, conductivity, and hydrophilicity. A highly flexible piezoresistive pressure sensor utilizing a porous structure made of polydimethylsiloxane (PDMS)/ carbon nanotube (CNT)/C₃H₈O₃ composites is introduced in this study. The porous structure was confirmed by field emission scanning electron microscopy. Response and release times were demonstrated to be rapid, approximately 43 ms and 62 ms, respectively. Mechanical testing revealed a tensile strength of 0.06 MPa and a Young's modulus of 0.0723 MPa, while the compressive strength was recorded at 0.0876 MPa with a Young's modulus of 0.142 MPa. Durability assessments indicated consistent performance across 6000 cycles and notable hydrophilicity. Compared to conventional PDMS hybrid CNT-based sensors, this new sensor exhibited improvements in flexibility and conductivity by approximately 50 and 40 times, respectively. Its applications include the detection of mouse button clicks, monitoring of human pinky joint motions, and recognition within pressure arrays. The sensor discussed holds significant potential for advancements in human-computer interaction and wearable technology sectors.

The need for materials with low density and high strength has drawn a lot of interest from researchers and industry in the last few years. Aluminum 6061 (Al6061) is one of these materials that has the required qualities. Powder-mixed electric discharge machining has become a practical choice for cutting such materials because of its versatile machining capabilities. However, this technique's excessive energy usage and poor cutting efficiency have drawn criticism. Furthermore, there are serious health and environmental risks associated with the typical dielectric (kerosene) used in EDM. Deionized water, a replacement to kerosene, has been used in this work to address the aforementioned problems, improving resource reusability and lowering the dielectric cost. Here, deionized water further makes the operation sustainable and protects the environment from harmful emissions produced during the machining process. Additionally, alumina (Al₂O₃) nano-powder has been mixed in dielectric and used to improve the machining responsiveness. Response surface methodology was used to carry out the investigation. The purpose of this study was to use microscopic analysis to examine the effects on the electrode wear rate (EWR) and accuracy index (AI). Analysis of variance (ANOVA) analyses for both responses revealed that all four parameters are highly significant, with p-values nearly zero (<0.05). Additionally, the coefficient of determination (R²) values for EWR (0.9611) and AI (0.9285) indicate that the proposed models are reliable. The parametric optimization by grey relational analysis (GRA) approach highlighted that the magnitude for EWR and AI is improved by 50.85% and 2.67%, respectively, when optimal condition (I_P: 5 A, S_V: 2 V, S_T: 3 µs, and C_P:1.5 g/100 ml) is set during EDM of Al6061. The proposed EDM model yielded 48.29% and 5.11% better outcomes than the conventional EDM model in terms of EWR and AI, respectively.

Beam-type piezoelectric energy harvesters (PEHs), particularly those utilizing piezoelectric materials, have garnered considerable attention as efficient devices for converting ambient mechanical vibrations into electrical energy. This comprehensive review article thoroughly examines the mathematical models employed in beam-type PEHs, emphasizing their evolution and limitations. The study also delves into both theoretical and experimental analyses of design configurations, placing a special focus on the impact of geometries on energy harvesting efficiency. In conclusion, the paper explores recent advancements and improvements, along with potential avenues for future research, providing a concise overview tailored for professionals and scholars engaged in this specialized field.

Inspired by the advances in microfabrication of microelectromechanical systems (MEMSs), microphysiological systems (MPSs) capitalized on the fabrication techniques of MEMS technology and pivoted to biomedical applications with select biomaterials and design principles. With the new initiative to refute animal testing and develop valid and reliable alternatives, MPS platforms are in greater demand than ever. This paper will first present the major types of MPSs in the cardiovascular research space, and then review the core design principles of such systems to closely replicate the in vivo physiology. Fabrication methodologies of the platform, as well as technologies that enable patterning and functionalizing scaffolds, and the various sensing modalities that can interface with such MPS platforms, are reviewed and discussed. This review aims to provide a comprehensive picture of cardiac MPSs in which microfluidics play an important role in the design, fabrication, and sensing modalities, and prospects of how this platform can continue to drive further improvements in cardiovascular research and medicine.

The demand for rapid, high-quality, and controlled mixing at the microscale has led to the development of various types of micromixers. Micromixers are commonly categorised as active, or passive based on whether they utilise external energy to enhance mixing. Passive micromixers utilise a complex geometry to enhance the diffusion coefficient at lower Reynolds numbers and induce chaotic advection at higher Reynolds numbers for effectively mixing fluids without external energy. Active micromixers, on the other hand, achieve precise, fast, and controllable mixing by employing external energy sources such as pressure, electric, magnetic, or acoustic fields. Some active methods such as magnetic field-driven micromixers need fluids with specific properties. Others, such as acoustic field-driven micromixers apply to various types of fluids. Bubbles can be used as membranes or stirrers in microfluidic devices for both passive and active micromixers. They are easy to use, compatible with microfluidic systems, low cost, and effective. Improvements in manufacturing methods, notably, 3D printing have emerged as promising methods for the development of new micromixer designs. In this paper, a wide range of micromixer types is reviewed and the main mechanism for enhanced mixing is investigated. This study aims to guide researchers proposing innovative designs. Furthermore, it is shown that combining different methods can lead to the development of more effective micromixers, promising further advancements in microscale mixing technology.

The burgeoning internet of things and artificial intelligence technologies have prospered a variety of emerging applications. Human–machine interfaces (HMIs), for instance, enables users with intuitive, efficient, and friendly way to interact with machines, capable of instant information acquisition, processing, communication, and feedback, etc. These features require ultra-compact and high-performance transducers, and therefore self-powered sensors have become the key underlying technology for HMI applications. This review focuses on the piezoelectric, triboelectric, and hybrid self-powered sensors with particular attention to their microstructures and fabrication methods, showing that both traditional microfabrication and emerging fabrication methods like three-dimensional (3D) printing, electrospinning, and braiding have contributed to the planar, array, porous, fabric, and composite type self-powered sensors. Moreover, the integration method of piezoelectric and triboelectric sensor arrays is investigated. The crosstalk issue is highlighted, i.e. the signal interference between adjacent sensing units, and current solutions such as array design optimization, signal processing improvement, and material innovation to reduce crosstalk sensitivity have been reviewed through specific examples. Three categories of HMI applications have been outlined, including intelligent interaction, robotics, and human monitoring, with detailed explanations of how the self-powered sensors support these HMI applications. Through discussion of challenges and prospects, it is proposed that further coordinating the design and fabrication of micro devices with HMIs will potentially boost the intelligent application with even higher level of diversification, convenience, and interconnectivity.

At the era of powerful computers, it is tempting to employ finite element models early in the design phase of a device. However, especially for MEMS devices, the dimensional ratios and short wavelengths compared to the device's dimensions, along with the involvement of multiple physics, can necessitate complex and computationally intensive models, making them impractical for optimization processes. Hence, reduced order models, like the lumped element model, are often preferred as they accurately represent complex system behaviour within a defined frequency range. This review explores the use of lumped element models and their corresponding electrical equivalent circuits for simulating MEMS electro-acoustic devices, offering insights into their diverse applications within this specific domain.

Transfer printing is a micro or nanofabrication technology used to transfer a thin film coated on a stamp to a substrate. The printing process requires a large adhesion force between the thin film and the substrate. In this study, we investigated the transfer printing of gold (Au) thin films via atomic diffusion bonding. An Au thin film coated on micro/nanoridges of a (h-) polydimethylsiloxane (PDMS) stamp was contacted with another Au thin film previously coated on a substrate. The two films strongly bonded via the interdiffusion of Au atoms, and the Au thin film on the stamp was transfer-printed with micro/nanopatterns onto the substrate under atmospheric conditions. The patterns have widths of 100 µm, 150 µm, and 150 nm and thicknesses of 30, 50, and 100 nm. We investigated the effects of the air-exposure time and stamp (indentation) modulus on the transfer-printing of line-patterned Au thin films. We found that longer air exposure increased the water contact angle and surface roughness of the Au thin films, indicating that air exposure induces contaminations and promotes water absorption, thereby decreasing a transfer rate of thin films. Both the Au-coated stamp and the substrate must be stored in a low-humidity environment before transfer printing. The modulus of the (h-)PDMS stamp was controlled by varying the ratio of the prepolymer and curing agent. A stamp with a lower modulus improved adhesiveness between the stamp and the substrate and provided a large contact area, thereby increasing the transfer rate and reducing the processing time. We successfully transfer-printed Au thin films with 150-nm-wide line patterns.

This paper presents an algorithm to improve the computational efficiency of electrostatically driven scanning micromirror with staggered vertical combs (SVC). Firstly, a single vertical comb is treated with an approximate periodic boundary. Through mechanical analysis, the mapping relationship between the deflection angle of the comb and the torque is obtained. It is found that when the deflection angle is small, the torque acting on the comb changes little and can be considered as a constant value. Based on the mapping relationship, the electrostatic torque of a single axis electrostatic scanning mirror with different voltages is extracted by considering only the electrostatic field action. In the subsequent deflection analysis of the micromirror, the extracted torque is added to the mechanical field, and the electrostatic field can be ignored. In order to further simplify the model and improve the computational efficiency, an equivalent model was established on the basis of the original single-axis scanning mirror. Immediately after, considering the effect of air damping, solid mechanics and thermal-viscous acoustic coupling calculations of the single-axis electrostatic driven mirror are carried out. Finally, the maximum mechanical deflection angle of the micromirror under different atmospheric pressure is obtained. The model proposed in this paper transforms the electro-mechanical coupling calculation into separate calculation of electrostatic field and mechanical field, which greatly improves the calculation efficiency.

Currently, micromachined ultrasonic transducers are classified as capacitive micromachined ultrasonic transducers (CMUTs) and piezoelectric micromachined ultrasonic transducers (PMUTs). CMUTs present higher electromechanical coupling coefficients, high receiving sensitivity, and higher bandwidth, exhibiting superior performance compared to PMUTs and their traditional counterparts. Micro-nano materials, with advantages such as high surface area, improved electronic performance, biocompatibility, and easy integration with miniaturization, are widely applied in various fields including electronics, energy, environment protection, and medicine. The combination of CMUTs and micro-nano materials has become a hot research topic in the fields of medicine and biochemistry in recent years. Integrating CMUT with micro-nano materials plays an important role in biochemical testing, drug monitoring, and medical diagnosis, promoting the prediction of disease progression and timely implementation of effective measures. This work primarily discusses the integration of cMUTs with micro-nano materials, emphasizing that the innovative application of these materials significantly enhances the performance of cMUTs, thereby advancing the development of related technologies.

This study investigates the fatigue life of cantilever-style hinges in digital micromirror devices (DMD), which are critical for their optical switching function. The hinges, which facilitate the rotation of reflective mirrors, are subjected to significant mechanical stress due to repetitive flexing, posing a risk of device failure. Prior to the main continuous bending fatigue test, a preliminary resonance-based fatigue experiment was conducted using microscopic laser Doppler vibrometry. The amplitude-frequency response of the cantilever-hinged micromirrors was measured, identifying a resonant frequency through Gaussian curve fitting. Operating at this resonant frequency, the micromirrors achieved stable performance more than 2×10¹⁰ oscillation cycles, with frequency stability throughout, affirming the reliability of the hinge structure under low-stress, high-cycle fatigue conditions. To further assess fatigue resistance, atomic force microscopy (AFM) was subsequently employed to conduct continuous bending fatigue tests, in which cyclic stress loading was applied to induce continuous bending in the cantilever hinges. Force-displacement curves obtained during the loading process were analyzed to determine the deflection and spring constants of the hinges at different stages of bending. Experimental results reveal that after 5×10⁵ continuous bending cycles, plastic deformation occurred in the hinges along the bending axis, with the end morphology of the hinge exhibiting a significant residual plastic deformation of 417.18 nm compared to its initial state. This research provides valuable insights into the high-stress, low-cycle fatigue behavior of nanoscale devices, contributing to the understanding and improvement of DMD reliability.&#xD;

The need for materials with low density and high strength has drawn a lot of interest from researchers and industry in the last few years. Aluminum 6061 (Al6061) is one of these materials that has the required qualities. Powder-mixed electric discharge machining has become a practical choice for cutting such materials because of its versatile machining capabilities. However, this technique's excessive energy usage and poor cutting efficiency have drawn criticism. Furthermore, there are serious health and environmental risks associated with the typical dielectric (kerosene) used in EDM. Deionized water, a replacement to kerosene, has been used in this work to address the aforementioned problems, improving resource reusability and lowering the dielectric cost. Here, deionized water further makes the operation sustainable and protects the environment from harmful emissions produced during the machining process. Additionally, alumina (Al₂O₃) nano-powder has been mixed in dielectric and used to improve the machining responsiveness. Response surface methodology was used to carry out the investigation. The purpose of this study was to use microscopic analysis to examine the effects on the electrode wear rate (EWR) and accuracy index (AI). Analysis of variance (ANOVA) analyses for both responses revealed that all four parameters are highly significant, with p-values nearly zero (<0.05). Additionally, the coefficient of determination (R²) values for EWR (0.9611) and AI (0.9285) indicate that the proposed models are reliable. The parametric optimization by grey relational analysis (GRA) approach highlighted that the magnitude for EWR and AI is improved by 50.85% and 2.67%, respectively, when optimal condition (I_P: 5 A, S_V: 2 V, S_T: 3 µs, and C_P:1.5 g/100 ml) is set during EDM of Al6061. The proposed EDM model yielded 48.29% and 5.11% better outcomes than the conventional EDM model in terms of EWR and AI, respectively.

Beam-type piezoelectric energy harvesters (PEHs), particularly those utilizing piezoelectric materials, have garnered considerable attention as efficient devices for converting ambient mechanical vibrations into electrical energy. This comprehensive review article thoroughly examines the mathematical models employed in beam-type PEHs, emphasizing their evolution and limitations. The study also delves into both theoretical and experimental analyses of design configurations, placing a special focus on the impact of geometries on energy harvesting efficiency. In conclusion, the paper explores recent advancements and improvements, along with potential avenues for future research, providing a concise overview tailored for professionals and scholars engaged in this specialized field.

Strain sensors have been developed in various fields by converting mechanical deformation into electrical signals. Surface acoustic wave (SAW) devices are beneficial for strain sensing due to their simplicity of fabrication and wireless operation capabilities. In this study, we investigate SAW strain sensors operating at 1.25 $\mathrm{GHz}$. The fabricated SAW resonators using standard photolithography technology are characterized with a custom-made cantilever setup capable of applying defined strain values up to approximately −4000 µε to 4000 µε. From these measurements, a high responsivity even up to this high strain values is demonstrated. We also explore the impact of geometric design parameters on strain-sensing performance. We vary the length of the SAW resonator and observe that the longer the SAW resonator, the more responsive the device gets to strain changes. When the distance between the two reflectors confining the SAW is 2207 $\mu\mathrm{m}$, the responsivity to strain is 114.99 $\mathrm{Hz}\,\mu\epsilon^{-1}$. In summary, this study investigates the feasibility of GHz SAW resonators as high-strain sensors on non-flexible substrates with a custom-built experimental setup, to evaluate their potential for future applications in extreme mechanical environments.

Lift-off process is an alternative to deposition, lithography, and etching of materials. Lift-off is a simple and economical process because it does not require subsequent wet or dry etching. Lifting-off nanometer thick films is a well-developed and repeatable process. However, lifting-off a few micrometer thick films may be challenging. Previously, different techniques were proposed to lift-off micrometer thick films. Herein, a novel method for lifting-off high thickness materials is proposed using a multi-layer AZ 5214E photoresist. The novel method was successful in lifting-off 4 µm thick copper while the copper could even be deposited up to 6 µm with tri-layer AZ 5214E. With four layers of AZ 5214E, the photoresist thickness can be even thicker than 9 µm. As detailed in the study, the photoresist layer thickness can be adjusted by varying the number of layers. This enables the selection of the appropriate number of layers to achieve the desired material thickness. To show the merits of the proposed method, the method is compared to the bi-layer method with AZ 4562 photoresist which is used for lifting-off high thickness materials. In addition to lifting-off thick materials, the proposed method is faster compared to lifting-off using bi-layer AZ 4562. Despite the ability to lift-off thick films, both methods could suffer from lift-off flags if the deposition process is not anisotropic. Solutions to remove the lift-off flags, and reduce the undercut width are demonstrated.

In this work, we report a method that enables a standard electrostatic microelectromechanical system (MEMS) device to perform complex sensing functionalities, such as detecting the presence of helium without a sensing material or a conditioning circuit. Helium is a noble, odorless, non-reactive gas that is very challenging to detect. It is used in critical applications such as storing nuclear fuel waste inside a dry cask. In these applications, its leakage from the dry cask may indicate the cask's safe operation's degradation. A departure from the common practice of exciting the MEMS around its mechanical resonance, the method is based on exciting the MEMS around its electrical resonance circuit. This method shows that the tiny difference between the air dielectric constant (1.000 59) and helium (1.000 067) corresponding to only a few Femtofarad level capacitances produces a 25 mV difference without a conditioning circuit. Simulation results confirmed those findings and explored the sensor response at different operation conditions. This method eliminates the need for a heated microstructure and the need for absorption material. This method is not limited to gas sensing. It can be applied to other sensing mechanisms, such as acceleration and pressure measurements, and eliminate the complex circuit to read small capacitance in these applications.

MEMS environmental sensors, including pressure, gas, and humidity sensors, require protection from mechanical damage, particle exposure, and condensing moisture, while maintaining their ability to exchange gases with the environment. This work introduces a novel packaging approach for MEMS environmental sensors using substrate-embedded filters made from microfine powders through PowderMEMS^® microfabrication technology. The study demonstrates the successful fabrication of gas permeable, functionalized PowderMEMS^® filters on 200 mm Si-wafers for wafer-level packaging of MEMS environmental sensors. Utilizing complete Si-wafers allows for all MEMS sensors on a device wafer to be packaged in a single substrate bonding step, followed by die singulation. The processed wafers are shown to be compatible with high-temperature glass-frit substrate bonding. Alternatively, individual chips with PowderMEMS^® filters can be assembled discretely onto standard semiconductor packages to serve as gas-permeable filters. Successful hydrophobation of the inherently hydrophilic PowderMEMS^® structures by deposition of hydrophobic nanofilms is demonstrated and resistance to water ingress is evaluated by immersion testing. Given that many MEMS gas sensors are cross-reactive to oxidizing gases like ozone, this study also explores the integration of ozone-degrading catalytic powder into the PowderMEMS^® filters. As a proof-of-concept, commercial MEMS ozone sensors are modified with catalytic PowderMEMS^® caps, and successful ozone degradation is demonstrated. While PowderMEMS^® processing is typically conducted on 200 mm Si-wafers, other suitable substrates include glass and (fiber-reinforced) polymers.

Kirigami design principles have been widely applied to develop thermally responsive shape-morphing devices across various scales. However, the multi-degree-of-freedom (multi-DoF) morphing capabilities of microelectromechanical-systems (MEMS)-scale kirigami devices under localized Joule heating remain largely unexplored. This paper presents a quadrant kirigami-type electrothermal MEMS actuator with multi-DoF morphing capabilities, demonstrating both one-dimensional piston motion and two-dimensional (2D) tilting motion. The actuator, fabricated using surface and bulk micromachining techniques, features four independent electrical circuits, creating four electrothermally separated quadrants within the MEMS-scale kirigami structure. The temperature distribution within each quadrant of the actuator, subjected to localized Joule heating, was experimentally examined using thermography, revealing distinct temperature contrasts. The actuator demonstrated multi-DoF morphing capabilities, achieving a 2D tilting angular displacement of approximately 10° at 70 mW and a vertical piston displacement of 1.5 mm at 135 mW. These experimental results validate that the electrothermal quadrant design, leveraging localized Joule heating, enhances the DoF morphing capabilities of kirigami-type electrothermal MEMS actuators.

Residual stresses can be advantageously used to permanently preload flexure micro-mechanisms in order to modify their deflection and stiffness. This paper presents a new preloading chevron mechanism (PCM) used to amplify the preloading effect of thin film residual stress. To evaluate the preloading performances of this structure, the deflection characteristics of buckled beams and flexure linear stages preloaded by a PCM is investigated experimentally. All the mechanisms are manufactured from a monocrystalline silicon substrate using deep reactive ion etching and residual stress is provided by wet thermal oxidation. Measurements show that the deflection magnitude of fixed-fixed oxidized silicon buckled beams can be increased by up to 5 times when a PCM is integrated. The flexure linear stages studied in this research are composed of a parallel leaf spring stage connected to two fixed-guided buckled beams preloaded by a PCM. Depending on the beam dimensions, the stage translational stiffness can be set to a specific value. We designed a near-zero positive stiffness linear stage revealing a measured stiffness reduction of 98%, and a bistable linear stage with a constant negative stiffness region. Thanks to the elevated preloading displacement supplied by the PCM, the operating stroke (actuation region where the stiffness remains constant) is relatively large (more than 0.4 mm travel for 2.59 mm leaf spring length). The analytical and numerical models carried out to design the mechanisms are in good agreement with the experimental data. The results show that the fixed frame stiffness has a significant effect on the preloading performances due to the substantial forces exerted by the PCM. Furthermore, the presented preloading concept, modeling and sizing method could be applied to other compliant mechanism designs, scales and materials, enabling applications in microelectromechanical systems and watchmaking.

Microlens arrays (MLAs) play a prominent role and are essential components in the fabrication of 3D imaging and optical systems. Traditional MLA patterns have limited applications, which prompts the demand for novel MLA patterns for advanced applications. The fundamental objective of this study is to demonstrate different types of MLA fabrication process within our department, employing custom-developed equipment for industrial applications. The three distinctive MLA patterns that were designed and developed are symmetrical, non-symmetrical and step-layer pattern MLAs. MATLAB and Auto CAD 2D software were used to design the MLA patterns, and they were developed on a 4 inch silicon wafer using maskless exposure lithography and thermal reflow techniques. The fabricated master mold acts as a template for replicating pattern molds on a glass wafer. Photoresist ma-p-1275 G and polydimethylsiloxane resin were used for pattern development on silicon wafer and glass wafer, respectively. The fabricated MLA patterns were characterized with an optical microscope and scanning electron microscopy. The fabricated MLA pattern replicas offer durability, longevity, reusability and scalability for large-scale productions. The current study offers a comprehensive approach to in-house production on different types of MLA pattern fabrications.

High-precision fabrication of nanoscale periodic structures is utilized in a wide range of applications, including wire grid polarizers, photonic crystals, and light-emitting diodes. Among the fabrication methods, laser interference lithography (LIL) is one of the most widely applied techniques for nanoscale periodic structures, due to its advantages of being maskless, low cost, having an infinite depth of focus, and the capability of large-area patterning with a single exposure. However, since LIL requires uniform illumination of the coherent laser light, the illuminating laser beam is typically expanded and only the central part with uniform intensity is used, rendering LIL low in energy efficiency. In this study, we introduced a simple and cost-effective design of beam-flattening device with tunable performance that improves the energy efficiency and throughput of LIL for fabrication of nanoscale periodic structures. The design of the device was based on thin-film interference, where device parameters were obtained from optimizing performance. The as-fabricated beam-flattening device demonstrated a 4-fold improvement in throughout, as compared to the conventional LIL method. The capability of fabricating large-area (2000 mm²) gratings demonstrated the scalability of our beam-flattening device. We expect our device to be readily integrable to LIL systems and applicable for a wide range of fabrication processes.