Abstract
Theories of electrokinetic phenomena on a soft surface, i.e., a hard surface covered with an ion-penetrable polyelectrolyte layer are reviewed. Electrokinetic flow between two parallel plates with soft surfaces is analyzed to derive analytic expressions for various electrokinetic quantities such as electro-osmotic velocity and streaming potential. These phenomena are characterized by two parameters, that is, the density of the fixed charges distributed in the surface layer and the softness parameter. An Onsager relation is found to hold between electro-osmosis and streaming potential. The physical meaning of the softness parameter is elucidated.
