Yangyang Wang
The Journal of Mechanical Science and Technology, vol. 23, no. 3, pp.874-884, 2009

Abstract : by solving the traditional Navier-Stokes equation subjected to the slip velocity induced by the electric-charged wall as a boundary condition. Recently, Suh and Kang (Physical Review E 77, 2008) presented the asymptotic solutions of the ion transport equations near a polarized electrode under the action of an AC field, and then proposed a new theoretical model of the slip velocity on the electrode considering the ion adsorption effect. In the present paper, we apply the model to a two-dimensional AC-electroosmotic flow in a microchannel to calculate the slip velocity on a pair of coplanar asymmetric electrodes embedded on the bottom wall, and then experimentally measure the slip velocity using the micro-PIV technique to validate the theoretical model. Comparison shows an excellent overall match between the theoretical and experimental results, except for on the narrow electrode at low frequencies. Next, we numerically perform parametric studies regarding the AC frequency, effective Stern-layer thickness and ion adsorption effect to further understand the characteristics of the AC electroosmotic flow. Results show that, as the frequency increases, the slip velocity also increases. In addition, the velocity decreases with increasing either Stern-layer thickness or ion adsorption effect.

Keyword : AC-electroosmosis; Effective Stern-layer thickness; Ion adsorption; Slip velocity; Particle image velocimetry (PIV)