Electromigration and micromixing through a constriction under time periodic electroosmotic flow

Mixing in a microchannel is a challenging task due to the small Reynolds numbers. A simple yet an efficient novel approach to enhance mixing has been proposed in this thesis. The concept was demonstrated in a T-type micromixer with a constriction introduced at the T-junction under time periodic electroosmotic flow induced by applied AC voltages. Mechanism of mixing enhancement and factors governing the mixing efficiency have been investigated. Numerical analyses of the proposed micromixer were conducted with finite element method. For an accurate simulation of flow behavior in a practical micromixer, the often neglected electromigration effect of charged solute/fluorescent dye must be considered. In view of the importance of the electromigration effect, a method to measure ionic mobility of the fluorescent dye has been adapted from the micromixer design. A new numerical formulation has also been developed to elucidate the mechanism behind the directional dependence of displacement time for two- fluid electroosmotic flow. DOCTOR OF PHILOSOPHY (MAE)