Virtual walls in microchannels.

Microfluidic channels were studied, in which the surface is modified from a solid/liquid interface into solid/liquid and air/liquid alternating interface, creating the equivalent of a superhydrophobic surface on the interior of the channel. The composite microchannel can be easily fabricated using embossing or cast molding of PDMS. The channels are stable under typical microfluidic conditions. For the most part, fluid flow behavior is not significantly changed; however, interesting mass transport effects can be observed in such channels under appropriate conditions. An application example of a microvalve based on the mass transport effect is demonstrated, showing advantages of simple design, fabrication, no moving part and zero dead volume.