Hydrodynamic interactions in metal rodlike-particle suspensions due to induced charge electroosmosis

We present a theoretical and experimental study of the role of hydrodynamic interactions on the motion and dispersion of metal rodlike particles in the presence of an externally applied electric field. In these systems, the electric field polarizes the particles and induces an electroosmotic flow relative to the surface of each particle. The simulations include the effect of the gravitational body force, buoyancy, far-field hydrodynamic interactions, and near-field lubrication forces. The particles in the simulations and experiments were observed to experience repeated pairing interactions in which they come together axially with their ends approaching each other, slide past one another until their centers approach, and then push apart. These interactions were confirmed in measurements of particle orientations and velocities, pair distribution functions, and net dispersion of the suspension. For large electric fields, the pair distribution functions show accumulation and depletion regions consistent with many pairing events. For particle concentrations of 10⁸ particles∕mL and higher, dispersion within the suspension dramatically increases with increased field strength.