Preliminary investigation of micropumping based on electrical control of interfacial tension

Electrical control of the interfacial tension between a liquid and solid (electrowetting) is studied as a means of microactuation for fluid systems, i.e. micropumping Electrowetting provides a means of direct fluid pumping with no moving mechanical parts, which may prove useful in a number of application areas, such as micro chemical dispensers, injectors, and reactors, and even cooling systems for high-density microelectronics. A test device has been built (with silicon micromachining) for the study of electrowetting, and a detailed model of the devices is given. The model describes liquid flow in a small channel, as governed by Navier-Stokes equations, Laplace's equation, Young's equation, and Lippmann's equation. Simulation results presented indicate that electrowetting is a viable approach to microactuation: in a 10 mu m radius channel, it may be used to generate pressures on the order of 0.01 MPa, comparable to pressures generated by existing micropump designs are order of magnitude larger in size. Although the dynamics of the test device are dominated by fluid friction, it is also shown that another micropump design, based on mercury, should behave as a nearly frictionless oscillator.<
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