Electrokinetic micropump and micromixer design based on ac faradaic polarization

A microfluidic pump and mixer design based on ac faradaic polarization is proposed. Unlike ac electrokinetic devices based on capacitive charging of the electrodes, the design yields a net electro-osmotic flow for high-conductivity electrolytes at high voltages and frequencies without producing gas bubbles or generating pH gradients. The average velocity, which can be more than an order of magnitude higher than that generated by the capacitive mechanism, has an exponential dependence on the voltage and increases monotonically at low frequencies. Vortices and net flows with linear velocities in excess of 1 mm/s are generated with orthogonal microfabricated planar electrodes based on the unique flow and polarization features of this new ac charging mechanism. (C) 2004 American Institute of Physics.