Sequential electrolytic bubble-based micro-pump dosing system

An electrolytic bubble actuated micropump has been fabricated and characterized for dosing applications. The micropump consists of a series of bubbles formed directly inside a microfluidic channel, and the volume displacement characteristics of inflating/deflating electrolytic bubbles are utilized to move the liquid along the channel. Prototype chips with five sequential bubbles were built using standard photolithography techniques. The pump performance was characterized as a function of the voltage required to generate electrolytic bubbles of varying size (3.5 -4.5 V), pulse-width (50-300 ms), time interval between pulses (50-300 ms), and backpressure; each parameter being varied independently. It was found that the size of the bubble, and hence the quantity of liquid displaced, increases with voltage. Also, the pump rate increases with a reduction in pulse-width and the time interval between pulses. The optimum pump rate of 24 nl/min, corresponding to a flow velocity of 640 μm/s, was obtained for the current channel size of 25×25μm in cross-section. The pump performed successfully against backpressures up to 107 kPa.