This exploratory research project will attempt to develop a technology for the formation of subnanoliter droplets of water-based liquids, and for the manipulation and transport of these droplets on the planar surface of a substrate chip, using the DEP force generated by time-varying voltages. This is in contrast to microfluidic research on closed-channel fluid hydraulic Sytems, which can be complicated to fabricate and difficult to integrate with other chip technologies. It is also in contrast to particulate DEP research on cell separation in a liquid medium. Preliminary experiments have shown that minute water droplets can be formed and transported at surprisingly high speeds, using rf applied voltages. Thus the perceived obstacles of high-field electrochemistry and heating can be avoided. However, these experiments also show that the dynamics of forming and transporting droplets using DEP are not well understood, and so it is not yet possible to estimate the limits of this technology. This research will pursue further experiments to elucidate these dynamics, varying the important parameters of electrode configuration, voltage waveform, and surface tension, as well as analytic and computer modeling of the processes involved. This new liquid handling capability is naturally integrated with VLSI circuitry and on-chip sensors, to enable a processor-on-a-chip where biofluids dispensed from a micropipette are divided into precisely controlled subnanoliter droplets, then transported about for microprocessor-control led onchip diagnostics, mixing, separations, and dispensing. The smooth surface of the chips affords good accessibility, ease of cleaning, and zero liquid waste. Or by reliance on inexpensive IC fabrication methods, it will be suitable for implementations where the chips are disposable items. These features imply broad applications in biomedical assays, pharmacology, biochemistry, cancer research, remote diagnosis, etc.
