FIELD-EFFECT ELECTROOSMOSIS

A novel effect, called field effect electroosmosis has been postulated. By coating the outside of a silica capillary with a conductive layer and applying a perpendicular voltage, V(G), across its wall, the zeta potential, can be changed by varying V(G). Through flexible control of the zeta potential, the electroosmotic flow can be controlled. This adds a new dimension to capillary electrophoresis (both capillary zone electrophoresis and micellar electrokinetic capillary chromatography). Some of the advantages, including tuneability, are discussed. Based on this effect, the design of the first electrokinetic transistor, called a metal-insulator-electrolyte-electrokinetic field-effect device (MIEEKFED), was proposed. This device could be used for separation-based sensors. It also has great potential for miniaturization, especially because of the advances that have occurred in the micromachining technology of silicon. Recently, an experimental study of the use of an additional electric field outside a capillary to control the zeta potential has been reported. This work provides confirmation of our theoretical predictions.