An electrolysis-bubble-actuated micropump based on the roughness gradient design of hydrophobic surface

A novel electrolysis-bubble-actuated micropump based on the roughness gradient design in the microchannel is reported in this paper. This micropump is implemented by taking advantage of both the electrolysis actuation and the surface tension effect. The surface tension effect is controlled via the periodic generation of electrolytic bubbles and the roughness gradient design of microchannel surface, which results in the specified variation of liquid contact angle along the microchannel. Our proposed micropump could resolve the disadvantages that exist in the early reported micropumps, such as the complicated time-sequence power control, the need of long nozzle-diffuser structure, and the choking/sticking phenomena of electrolytic bubbles in a microchannel. Due to the features of large actuation force, low-power consumption, and room temperature operation, our micropump is suitable for the development of low-power consumption and compact micropumps for various applications. Experimental results show that the liquid displacement and the pumping rate could be easily and accurately controlled by adjusting the amplitude and frequency of the applied voltage. With the applied voltage of 15 V at 4.5 Hz, a maximum pumping rate of 114 nl/min is achieved for one of our micropump designs with a microchannel of 100 x 20 mu m. In this paper, we report the theoretical analysis, design, micromachining process, operating principles, characterization, and experimental demonstration of these micropumps.