Shear-induced enhancement of self-diffusion in interacting colloidal suspensions

Abstract

We set up the generalized Langevin equations describing coupled single-particle and collective motion in a suspension of interacting colloidal particles in a shear flow and use these to show that the measured self-diffusion coefficients in these systems should be strongly dependent on shear rate ε^.. Three regimes are found: (i) an initial const+ε^.2, followed by (ii) a large regime of ε^.½ behavior, crossing over to an asymptotic power-law approach (iii) D₀-const×ε^.-½ to the Stokes-Einstein value D₀. The shear dependence is isotropic up to very large shear rates and increases with the interparticle interaction strength. Our results provide a straightforward explanation of recent experiments and simulations on sheared colloids.