Autonomous microfluidic control by mixed potentials generated on composite metal electrodes

A new concept and devices for autonomous switching of valves and pumps in microfabricated flow channels are proposed. An electrowetting-based valve consisting of gold and zinc opened when an electrolyte solution reached the zinc part in a controlling flow channel and a mixed potential was applied to the gold valve electrode. Clock circuits that open the valves at predetermined times and logic circuits have been realized. A bubble micropump that moves a solution forward and backward was also constructed with three flow channels in which platinum black, zinc, and silver electrodes connected with each other. The technique was also used to create a device that ejects a solution in response to the concentration of creatinine and urea.