A bidirectional silicon micropump

In this paper we present a bidirectional silicon micropump. It consists of an electrostatically actuated displacement unit and two passive check valves. The difference to other wellknown diaphragm pumps, which are known as unidirectional pumps, is the layout of the valves. We designed a flap valve with a first mechanical resonance frequency between 1 WIZ and 2 WIZ (in the fluid environment). At low actuation frequencies (0,l Hz 800 Hz) the pump works in the forward mode. At higher frequencies (2 kHz - 6 kHz) the pump operates in the reverse direction. This is due to a phase shift between the responds of the valve and the pressure difference which drives the fluid. Investigating different pump layouts we achieved maximum pump rates in forward (reverse) direction of 250 (350) pYmin and 850 (200) flmin. The msori" back pressure is 3 10 hPa in forward and 70 hPa in reverse direction.