Numerical Models for AC Electro-Osmotic Micropumps

AC electroosmotic pumping of fluids in a microchannel with two thin coplanar electrodes, deposited on one dielectric wall and placed in an aqueous solution, is studied in this paper. Two different numerical formulations are compared. In the first one, the transport equations (mass, molar and momentum balances) for the ion concentration and Poisson equation for the electric field are solved simultaneously in the time domain without any simplification of the computational domain except that the dielectric walls are neglected. In the second one, a time average model is assumed and the electric double layer (Debye layer) is represented by an approximate one- dimensional model. In both cases, the finite element method implemented in the COMSOL commercial software is used as a numerical tool. The results for the electric field, space charge and velocity distributions are compared with a qualitative agreement between both models.