A bidirectional silicon micropump

Abstract 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 μl min -1 in the forward direction as well as 400 and 200 μl min -1 in the reverse direction. The maximum back pressure is 31 000 Pa (3.1 m H 2 O) in the forward and 7000 Pa (0.7 m H 2 O) in the reverse direction.