Suppression of reverse flows in pumping by induced-charge electro-osmosis using asymmetrically stacked elliptical metal posts.

Several researchers have analyzed pumps that employ induced-charge electro-osmosis (ICEO) using mainly coplanar electrode array structures in a lateral electric field. We propose ICEO pumps that remove reverse flows using asymmetrically stacked elliptical metal posts and numerically examine the pumping performance. By the boundary element method along with double layer approximation, we find that the asymmetrical stacking configuration efficiently suppresses the unwanted reverse flow and yields velocities of the order of a few millimeters per second, and this configuration is compatible with that of an optimized half-coating pump. Further, we propose a simple model for the stacking pump and predict that the velocity of such a stacking pump with a thin limit is larger than 67% of that of a circular cylindrical half-coating pump of the same length. Using this stacking pump, we can expect to significantly improve the pumping performance.