| The miniaturization and automation of chemical and biochemical laboratory instrumentation and processes has emerged as an important research topic in recent years. While numerous microfabricated fluid handling components to enable chip-based laboratories have been reported, the integration and reconfiguration of these diverse components remains a very challenging problem. Drawing upon analogies from microelectronics, this dissertation proposes an alternative organizational principle for the design, implementation and operation of complex and reconfigurable microfluidic systems. “Digital microfluidics,” based upon independent manipulation of discrete units of fluid (droplets) under a set of simple and well-defined operations, offers significant advantages over conventional continuous-flow microfluidics. In order to demonstrate the feasibility of digital microfluidics, this work describes the design, fabrication and testing of a planar microactuator structure for droplet manipulation based upon the electrowetting effect. Manipulation of droplets under direct electrical control without the use of pumps, valves, or fixed channels was demonstrated for electrolyte droplets ranging in size from 3 nl–3 μl. Average droplet velocities in excess of 10 cm/s were obtained at voltages as low as 60 V. The effect of various geometrical parameters and liquid properties on droplet transport rates was measured and analyzed. Other droplet-based operations including mixing, splitting, merging, and formation of droplets from a continuous source were also demonstrated. Thus, this technology permits monolithic integration of multiple microfluidic functions within a single chip. Important practical systems issues including droplet detection, solvent compatibility and droplet stability were also experimentally addressed in this work. |
