Low-voltage dynamic control for DC electroosmotic devices

Electroosmotic micropumps can find wide applications in laboratories-on-a-chip. While much progress has been accomplished, local and reconfigurable control of fluids remain an active research area in microfluidics, as this ability is essential to mixing and convection to speed up the reaction or analysis processes. This paper explores field-induced electroosmosis, also known as gate control technique, to achieve dynamic flow control. The gate-controlled electroosmotic devices are built using modified soft lithography technique. The gate electrode directly contacts the fluids, providing high efficiency in modulating zeta potential at the fluid-channel interface and hence efficient flow regulation. The flow velocity can be locally manipulated by applying low gate voltages (−2 V to +2 V). The flow rates are improved by 112% with negative gate voltages (0 V to −2 V), 0.61 μL/min up to 1.29 μL/min. The flow reversal is observed to start at an applied gate voltage of about +1.3 V. Moving fluid back and forth will greatly enhance mixing. The device design is scalable to accommodate various applications, portable in size, and can be readily interfaced with other microfluidic components, suitable for LOC applications.