An electrolytically actuated micropump

Abstract

An electrolytically actuated bubble micropump capable of precise dosing at high pumping speed is discussed. The fluid displacement is achieved by sequentially generating electrolytic gas bubbles directly inside the microfluidic channels. The operation of the pump thus requires no moving mechanical parts. A series of phase-shifted dc voltage pulses (ranging from 3.3 to 4.5 V) were applied to inflate the bubbles. Results show that the liquid displacement and pumping rate can be easily and accurately controlled by adjusting the applied voltage, pulse width, and pulse interval. An optimized pump rate of 24 nl/min, corresponding to a flow velocity of 640 μm/s was achieved for a channel size of $\text{25×25\hspace{0.17em}μ}\mathrm{m}$ in cross section. The measured volume displacements and pump rates were found to be in close agreement with the Faraday bubble growth mechanism. Results also show that the pump can reliably operate at high backpressure (up to 110.1 kPa), and a decrease in pump rate due to elevated backpressure can be offset simply by a small increase in voltage or pulse width.