Faradaic AC Micro-Pumps and Mixers With Orthogonal Electrodes

A new electrolyte AC micro-pump and mixer design based on Faradaic reaction polarization is investigated. The non-uniform AC electric field generated by electrode reaction polarizes the electrode surface, exerts a net electric force on the polarized layer and drives a net AC electro-osmotic flow of the electrolyte on the planar microelectrodes. At large electric potentials (>10V) and frequencies of 100 kHz to 1MHz, the flow direction is shown to be opposite to (previously reported) AC pumps due to capacitive charging. Moreover, the velocity has an exponential dependence on the applied electric potential due to the reaction and is hence an order of magnitude higher than the velocity driven by capacitive charging, which has a quadratic dependence. Theoretical analyses demonstrating the possibility of this Faradaic mechanism and some preliminary experimental results are presented.