Monday, 31 October 2005 - 12:30 PM
55a

Hydrodynamic Interactions in Colloidal Dispersions of Conducting Rods under Induced-Charge Electrophoresis

David Saintillan1, Eric Darve1, and Eric S. G. Shaqfeh2. (1) Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, (2) Departments of Chemical and of Mechanical Engineering, Stanford University, Stanford, CA 94305

Theory and numerical simulations are used to study the dynamics of a colloidal dispersion of conducting rods in an electric field. The polarization of a conducting particle results in the formation of a dipolar charge cloud on its surface, leading to a non-linear fluid slip velocity, which causes particle alignment and creates a disturbance flow. We derive a slender-body formulation accounting for this phenomenon, which is termed ‘induced-charge electrophoresis' after Squires and Bazant (J. Fluid Mech. 509, 2004). In particular we show that the effects of the slip can be modeled by a linear distribution of point-force singularities along the particle axis, resulting in a stresslet flow. Based on this slender-body model we perform numerical simulations of multiparticle systems that include far-field and near-field hydrodynamic interactions as well as Brownian motion. Simulations at infinite Peclet number (i.e. negligible Brownian motion) show that particle pairing occurs in the suspension as a result of the disturbance flow. The finite Peclet number case is also considered, and results are reported on pair probabilities, orientation distributions and diffusivities.

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