Effect of hydrophilicity on electrically driven flow in microchannels

In this study, the influence of different surface hydrophilicity on flow rate of microchannel was investigated. Rectangular microchannel was made by only PDMS (polydimethylsiloxane). In making microchannel, the patterned PDMS and the bottom PDMS were treated by argon plasma and then coated by allyl alcohol (99%) in the vacuum plasma instrument. PDMS surface contact angle was controlled by the change of power density during the vacuum plasma treatment process. The length and the width of microchannel were changed but the depth of microchannel was fixed at 100 μm. Several different external voltages were applied to investigate the flow rate change in microchannel. te of the channel length change, flow rates of microchannels were practically same at the same electric field. But microchannels, of which PDMS surface contact angles were 20° and 80°, showed different flow rates at the same electric field. Such flow rate difference was explained by relative zeta potential to show the effect of surface hydrophilicity change. This result showed that surface contact angle change affects the flow rate change of fluid in microchannel.