Nonlinear studies of AC electrokinetic micropumps

Recent experiments have demonstrated that AC electrokinetic micropumps permit integrable, local, and fast pumping (velocities $\sim$~mm/s) with low driving voltage of a few volts only. However, they also displayed many quantitative and qualitative discrepancies with existing theories. We therefore extend the latter theories to account for three experimentally relevant effects: $(i)$ vertical confinement of the pumping channel, $(ii)$ Faradaic currents from electrochemical reactions at the electrodes, and $(iii)$ nonlinear surface capacitance of the Debye layer. We report here that these effects indeed affect the pump performance in a way that we can rationalize by physical arguments.