Field-effect flow control in polymer microchannel networks

A new method for dynamic modulation of electro-osmotic flow (EOF) in plastic microchannel networks has been developed. The method employs field-effect flow control (FEFC) to adjust the zeta potential at the microchannel wall simply by biasing a gate electrode separated from the flow channel by a dielectric Parylene C film. The utility of this method is demonstrated by generating induced pressure-driven flow created by a differential EOF pumping rate. By varying the voltages applied to the FEFC gate electrodes in two microchannels at a T-intersection, the induced pressure at the intersection generates pumping in the connected third, field-free microchannel. The FEFC gate electrodes are able to change the magnitude and direction of the pressure pumping by inducing either a negative or positive pressure at the intersection. The flow velocity is tracked by neutralized fluorescent microbeads in the microchannels. The method described here provides an elegant mechanism for flow control in complex plastic microchannel networks. Furthermore, the ability to induce pumping by differential EOF provides important benefits for applications where zero electric fields must be maintained in the main flow channel, for example for example in the presence of high ionic mobility solutions.