Microfluidic field-effect flow control (FEFC) modifies the ξ potential of electroosmotic flow using a transverse electric field applied through the microchannel wall. Previously demonstrated in silicon-based and glass microsystems, FEFC is presented here as an elegant method for flow control in polymer-based microfluidics with a simple and low-cost fabrication process. In addition to direct FEFC flow modulation, independent transverse electric fields in connected microchannels are demonstrated to produce a differential pumping rate between the microchannels. The different electroosmotic pumping rates formed by local ξ potential control induce an internal pressure at the microchannel intersection, resulting in hydrodynamic pumping through an interconnecting field-free microchannel. Modulation of the voltages applied to the gate electrodes adjusts the magnitude and direction of the bidirectional pressure pumping, with fine resolution volume flow rates from -2 to 2 nL/min in the field-free microchannel demonstrated.
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