Particle Polarization and Nonlinear Effects in Electrorheological Suspensions

Abstract

The phenomenon of electrorheology (ER), described in the guest editors' introduction to this issue, can largely be explained by electrostatic interactions between particles by an externally applied electric field. The purpose of this article is to review particle-polarization mechanisms active in ER suspensions and to highlight some poorly understood electrostatic phenomena that inhibit the commercialization of ER technology.Figure 1 plots the apparent viscosity of a 20-wt% suspension of alumina particles in silicone oil as a function of shear rate for different electric field strengths. The viscosity changes are most pronounced at small deformation rates. At small shear rates the viscosity is proportional to E2 where E is the electric field strength.