A bidirectional silicon micropump

In this paper we present a bidirectional silicon micropump. It consists of an electrostatically actuated diaphragm and two passive check valves. It differs from other well-known diaphragm pumps, generally referred to as unidirectional pumps, in the layout of the valves. We have designed a flap valve with a first mechanical resonance frequency between 1 and 2 kHz (in the fluid environment). At low actuation frequencies (0.1-800 Hz), the pump works in the forward mode. At higher frequencies (2-6 kHz) the pump operates in the reverse direction. This is due to a phase shift between the response of the valves and the pressure difference that drives the fluid. Investigating different pump layouts, we achieve maximum pump rates of 250 and 850 mu l min(-1) in the forward direction as well as 400 and 200 mu l min(-1) in the reverse direction. The maximum back pressure is 31000 Pa (3.1 m H2O) in the forward and 7000 Pa (0.7 m H2O) in the reverse direction.