MR fluid structure in quasi-2D

Massachusetts Institute of Technology - 77 Massachusetts Ave., Room 66-456 Cambridge, MA 02139, USA

Received: 24 July 2006
Accepted: 7 November 2006

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.