Influences of the size and dielectric properties of particles on electrorheological response

The influences of the size and dielectric properties of particles on the electrorheological (ER) response are investigated by computer simulations. Our studies show that, in the case of two dimensions, the field-induced shear stress $\tau$ of one-component ER fluids can be expressed as $\tau \sim n{\sigma }^3,$ where n is the concentration of particle number and $\sigma$ stands for the diameter of particles. Compared with one-component ER fluids, $\tau$ is reduced for ER fluids consisting of two kinds of particles with different sizes. When small particles are in the minority, the reduction of the shear stress can be attibuted to two reasons: one is the weakening of chains, and the other is related to the shortening and thickening of chains. The latter can explain the reduction of the shear stress for two-component ER fluids, containing a few large particles. For ER fluids consisting of two kinds of particles with different dielectric properties, there is an approximately linear relation of $\tau$ to the particle concentration ratio.