Bistable microvalve with pneumatically coupled membranes

The paper reports on a novel bistable electrostatic actuator with pneumatic coupling. Two buckled Si/SiO/sub 2/ membranes span over connected air filled cavities with enclosed driving electrodes. The membranes operate in counteraction. If one electrode is pulled down electrostatically, the other is pushed up pneumatically, and vice versa. The actuator module is designed to achieve a deflection of /spl plusmn/10 /spl mu/m and will be integrated in a microvalve for liquids. With first completed actuator modules the electrostatic/pneumatic driving principle could be demonstrated. Grey-tone lithography has been developed to fabricate curved driving electrodes on the cavity bottom. It is calculated that compared to flat electrodes the driving voltage then can be reduced up to a factor of five. The curved cavity bottom also improves the pneumatic coupling since the enclosed air volume is minimized.