AC electrokinetic forces, such as AC electroosmosis (AC EO), AC electrothermal (AC ET) and dielectrophoresis (DEP) have been intensively investigated in manipulation of microfluids and micro/nanoparticles. AC EO effects are prone to manipulate relatively dilute electrolytes while AC ET effects extend the manipulation into conductive fluid domain. In the case of pumping high conductivity fluid, electric traveling wave signals on interdigitated electrode arrays and single-phase AC signals on asymmetric electrode structures are the two reported methods for AC ET based fluidic manipulation. This paper presents numerical simulation of the AC electric field induced electrothermal fluidic motion and pumping capacity of high conductivity fluids with stepped asymmetric electrode arrays. We investigated the effects of electrode profile and layout on pumping action and temperature rise distribution. Forward pumping mode and backward pumping mode are identified theoretically and numerically. Compared with the planar asymmetric electrode arrays, utilization of steps on electrode profile can result in significant improvement on the pumping capacity.

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