Notes from IEDM, part 2

Some of the most interesting applications for microelectromechanical systems occur at the interface between electronics and biology. "Lab on a chip" designs promise to bring the cost savings of bulk thin film processing to DNA testing and other analytical applications. Integrating living cells with electronic components would give cell researchers powerful new tools, with longer term potential for neuroprosthetics. But first, designers have to integrate two regimes which are fundamentally incompatible.

Papers at the IEEE Electron Device Meeting, held this week in Washington, DC, illustrated the enormous range of potential applications. One group, at the Max Planck Institute for Biochemistry in Munich, has placed individual neurons in defined locations on a semiconductor array, and has managed to guide the growth of synapses along desired pathways. They have shown that they can transmit signals from the silicon through the resulting neural network. Another group, at the Demokritos Institute in Greece, has used SiN fibers to detect labeled biomolecules.

DNA research is an especially important area for bioMEMS. Conventional electrophoresis methods for separating DNA strands take ten hours or more and require expensive equipment. A group at Princeton University has accomplished the same process in a matter of seconds using a microfluidic array with tunable electric fields. Researchers in Singapore have accomplished the polymerase chain reaction, used to duplicate DNA strands of interest, in a micromachined reactor suitable for integration with silicon electronics.

More general microfluidic systems require analogs to conventional chemical bench components such as reaction vessels, dispensers, pumps, and valves. Researchers at Duke University have used an array of switchable electrodes to create, transport, and mix individual droplets. The droplets, held together by their surface energy, can be cycled through the array at rates in excess of 1 kHz.