Induced-Charge Electrokinetic Phenomena: Theory and Microfluidic Applications

We give a general, physical description of "induced-charge electro-osmosis" (ICEO), the nonlinear electrokinetic slip at a polarizable surface, in the context of some new techniques for microfluidic pumping and mixing. ICEO generalizes "ac electro-osmosis" at microelectrode arrays to various di-electric and conducting structures in weak dc or ac electric fields. The basic effect produces microvortices to enhance mixing in microfluidic devices, while various broken symmetries--controlled potential, irregular shape, nonuniform surface properties, and field gradients--can be exploited to produce streaming flows. Although we emphasize the qualitative picture of ICEO, we also briefly describe the mathematical…