Electrorheology of a model colloidal fluid

Abstract We report experimental and theoretical results on the steady and oscillatory shear viscoelasticity of a model electroheological fluid. Details of the fluid synthesis, via the nucleation and growth of monodisperse silica spheres, and light scattering studies of the spheres are also presented. The shear-thinning viscosity μ shows a power-law dependence μ ∼ γ −Δ on the inverse strain rate γ, with Δ in the range 0.68-0.93. Likewise, the frequency-dependent viscosity μ(ω) shows a power-law dependence μ(μ) ∼ ω −Δ with Δ in the range 0.73-1.0. A theoretical treatment of steady-state cluster formation in applied electric and shear fields predicts the observed power-law dependences of the steady and oscillatory shear viscosities, albeit with exponents Δ = Δ = 2 3 .