ELCTROOSMOSIS - VELOCITY PROFILES IN DIFFERENT GEOMETRIES WITH BOTH TEMPORAL AND SPATIAL-RESOLUTION

A theoretical framework for the description of the phenomenon of elect ro-osmosis is developed. The main emphasis of the work is to develop r elations that describe the time and spatial resolution of the velocity of the liquid in contact with a charged surface when a train of elect ric field pulses are applied parallel to the surface. The work is moti vated by the recent development of NMR detected electrophoresis to a p owerful tool in the field of colloid chemistry. In this approach one e mploys pulsed electric fields, and the process of electro-osmosis is a complication. In developing this framework, we make use of results fr om electro-osmosis outside a single charged plane and in a slot, when the electric held is applied as a step-function. Results for both plan ar and cylindrical geometries are presented. In both cases we present results without and with effects due to counterflow taken into account . Finally, we compare the results of our theoretical description with some recently published velocity profiles obtained from NMR imaging te chniques. (C) 1996 American Institute of Physics.