Liquid dielectrophoresis on the microscale
نویسنده
چکیده
Polarizable liquids respond to a non-uniform electric "eld by collecting preferentially in regions of maximum "eld intensity. This manifestation of dielectrophoresis (DEP) is a wellknown example of the ponderomotive force, with the "eld acting on individual (molecular) dipoles in the liquid. When electrode dimensions are scaled down to &10 to 100 m, liquid DEP makes possible a new type of high-speed, micro#uidic liquid actuator. Of particular interest is that these devices can operate successfully with water-based media which are conductive. DEP microactuation is very fast; nanoliter droplets form in &0.1 s and transient velocities of liquid menisci exceed 5 cm/s. Joule heating is a problem, though proper electrode design and an operational mode where voltage is applied for very short time periods e!ectively controls temperature rise. The transient #ows that occur when voltage is applied are not well understood. Capillarity strongly in#uences the hydrostatics and dynamics, and surface wetting, which is a!ected by rf discharges on the dielectric surface, is also important. 2001 Elsevier Science B.V. All rights reserved.
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