Many droplet-based microfluidic schemes use the electrowetting-on-dielectric (EWOD) mechanism to dispense and transport droplets of conductive liquids. In applications where surfactant must be added to water, there are serious impediments to the droplet-dispensing process. The problem is a persistent membrane of fluid that forms between the reservoir and the droplet, spanning the top and bottom electrode surfaces. As the surfactant concentration approaches the critical micelle concentration, rupturing this membrane becomes increasingly difficult. This problem is resolved by embedding a thin resistive-heater element into the lab-on-chip device to assist the EWOD forces in creating droplets. When a dc current is applied to the heater strip, the membrane destabilizes and releases the droplet within ～0.5 s.
展开▼
