Many integrated microchemical systems require bulky ancillary equipment for operation. Here, we report an electrostatic microvalve that is fabricated exclusively with soft-lithographic techniques and can be directly integrated on polyer-based microfluidic devices. Used in conjunction with a battery pack and integrated circuits, the electrostatic valve has the potential to adapt a variety of miniaturized analytical platforms to a portable format. The valve will be especially relevant to applications regarding point-of-care diagnostics and mobile chemical detection.
The electrostatic microvalve design consists of a circular elastomeric membrane with an embedded electrode suspended above a microfluidic channel. A second electrode is embedded just below the bottom of the valve chamber. Applying an electric potential between the parallel electrodes causes an electrostatic attraction that pulls the compliant upper electrode towards the channel floor and constricts flow. We tested arrays of electrostatic microvalves with varying channel heights, membrane diameters, and membrane thicknesses to study the influence of microvalve geometry on actuation potentials in air and a hydraulic fluid. Results agree well with an analytical model that we developed. Currently, we can actuate the microvalves with electric potentials as low as 20 V. We also tested the pressures that the electrostatic valves were capable of accommodating during operation. The microvalve can be used in a variety applications, such as in arrays for addressing pneumatic or hydraulic microactuators, or in platforms for manipulating biochemical solutions for analysis.