| Abstract
| - Diffusiophoresis of a spherical colloidal particle normal to a plane subject to a uniform electrolyte concentrationgradient is investigated theoretically for arbitrary double layer thickness and surface potential. The governinggeneral electrokinetic equations are put in terms of bipolar spherical coordinates and solved numerically witha pseudospectral method based on Chebyshev polynomial. The effects of key parameters are examined suchas the double layer thickness, surface potential, and the distance between the particle and the plane. It isfound, among other things, that the presence of the boundary has a retardation effect on the motion of theparticle, provided that the double layer does not touch the planar boundary. If it does, however, the velocityof the particle will exhibit a maximum as the double layer just loses touch of the plane, thanks to the competitiveforce of the polarization effect. The planar boundary poses not only as a conventional hydrodynamic retardingforce, but also may distort the shape of the double layer greatly, hence altering its polarization situation,which has a profound electrostatic impact on the motion of the particle when it is close to the plane.
|
