Pumping liquids using asymmetric electrode arrays

Following a general symmetry argument, I suggest using locally asymmetric e lectric geometries to pump liquid in channels or drive droplets on surfaces . This strategy, which requires no global gradient in the pumping direction , should be of interest for microfluidic devices and micro-electro-mechanic al systems. A practical realization consists in using polar periodic arrays of electrodes addressed by an ac voltage difference. A simple electro-osmo tic model provides an estimate of the pumping velocities achievable.