Ultrafast micropumping by biased alternating current electrokinetics

This paper reports dramatic improvements in flow rate over conventional alternating current (ac) electrokinetic micropumps by exploiting asymmetry in electric potentials over the electrodes. A micropump consisting of a planar asymmetric electrode array was tested using ac signals with and without a direct current (dc) bias. All experiments were done at 100 kHz V-ac. The pumping velocity is much faster with a dc voltage, in some cases by an order of magnitude, reaching a linear velocity of up to 2.5 mm/s with only 5.4 V-rms. The discovery presents an exciting opportunity for microfluidics. Future improvement can be anticipated with additional optimization.