Abstract
We study the effects of quasi-two-dimensional (quasi-2D) confinement on the self-assembly of super paramagnetic colloids found in magnetorheological (MR) fluids using the Brownian dynamics simulation technique. A uniform external magnetic field is directed normal to a thin-slit in which dilute MR fluid is confined. The thickness of the confining slit ranges from a single colloid diameter to several colloid diameters. The steady-state structure that forms under such extreme confinement is shown to depend heavily upon the thickness of the slit. As the slit-thickness is increased from one colloid diameter (2D confinement) the structure of the dilute MR fluid changes non-monotonically. We introduce a ground-state model to predict the structure as a function of the slit-thickness and the volume fraction of the fluid. The model is able to quantitatively predict the structures observed in our simulations.
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