Effect of the Double Layer on the Dielectrophoretic Motion of Particles

Most suspensions involve the formation of ionic double layers next to the surface of particles. The double layer formed due to the induced-charge on the particle affects its motion even under sinusoidal electric fields through a phenomenon termed as induced-charge electro-osmosis. A method to numerically evaluate the effect of the double layer on the dielectrophoretic motion of particles has been developed. The technique, developed herein, involves a matched asymptotic expansion of the electric field near the particle surface, where the double layer is formed, and is written as a jump-boundary-condition for the electric potential when the thickness of the double layer is small compared to the size of the particle. The developed jump-boundary-condition is amenable to numerical evaluation and has been implemented in an Arbitrary Lagrangian Eulerian based finite element scheme using a discontinuous Galerkin method which naturally permits for such discontinuous boundary conditions in its formulation. The effect of the induced-charge electro-osmosis on the dielectrophoretic motion of particles has been observed using this technique.