Flow regulation in microchannels via electrical alteration of surface properties

The development of microfluidic (lab-on-a-chip) technology requires local control of fluid flow in the microchannels. Conventional microvalve approaches involve moving parts and/or complicated fabrication techniques, which makes them unreliable and prevents inexpensive integration in microanalytical systems. We have developed a simple low cost method for regulating fluid flow in microchannels that is compatible with existing microfabrication techniques and eliminates the need for moving parts. We use an electrical signal to stimulate silver deposition on a thin solid electrolyte layer in a small region of a microchannel. Since fluid flow is dominated by the nature of the channel surface, the electrodeposited silver changes the fluid-surface interaction and the effect can be used to control the movement of the fluid. Increases in the contact angles of both water and methanol, by 20° and 27° respectively, have been demonstrated. Such changes in hydrophobicity are sufficient to retard or stop capillary or external pressure-driven fluid flow in typical microchannels.