Electroosmotically-Driven Creeping Flows in a Wavy Microchannel

We report our investigation on electroosmotic flow (EOF) in a wavy channel between a plane wall and a sinusoidal wall. An exact solution is obtained by using complex function formulation and boundary integral method. The effects of the channel width and wave amplitude on the electric field, streamline pattern, and flow field are studied. When a pressure gradient of sufficient strength in the opposite direction is added to an EOF in the wavy channel, various patterns of recirculation regions are observed. Experimental results are presented to validate qualitatively the theoretical description. The solution is further exploited to determine that the onset condition of flow recirculation and the size of the recirculation region. It is found that they are dependent on one dimensionless parameter related to forces (K, the ratio of the pressure force to the electrokinetic force) and two dimensionless parameters related to the channel geometry (the ratio of the wave amplitude to the wavelength, and the ratio of the channel width to the wavelength).