Electrofriction and Dynamic Stern Layers at Planar Charged Surfaces

Using dynamic simulations, the electrophoretic mobility of counterions at a substrate with fixed or mobile surface charges under the action of a lateral electric field is studied. The lateral charge inhomogeneity and corrugation of the substrate is taken into account. Because of the pronounced electrofriction between counterions and surface ions, a large fraction of counterions is practically immobilized for highly charged substrates. This explains the experimentally observed saturation of the electrophoretic mobility of charged particles in the limit of high surface charge density.