We present experimental and theoretical results on the shear thinning of electrorheological fluids. Rheological measurements on a model fluid consisting of monodisperse silica spheres immersed in a dielectric liquid show a power-law dependence μ∝γ${\mathrm{̇}}^{\mathrm{-}\mathrm{\Delta }}$ of the apparent viscosity μ on the strain rate γ̇, with Δ in the range Δ=0.68–0.93. We present a theoretical treatment of steady-state cluster formation in applied electric and shear fields, which correctly predicts the observed power-law shear thinning albeit with an exponent Δ=2/3. We observe no true yield stress in this material.

• Received 5 November 1991

DOI:https://doi.org/10.1103/PhysRevLett.68.1519