March 2007

Fast, Bendable Computers

Military antennas are the closest application.

By Kate Greene

Transistors made of superthin silicon and applied to a flexible plastic substrate are fast enough to send and receive Wi-Fi signals. Credit: Zhenqiang Ma, University of Wisconsin-Madison

A Already, flexible-but-slow polymer electronics have made their way into technologies like roll-up digital displays. If superfast silicon electronics could also be made flex­ible, we might be able to do things like weave computing devices into clothing, or mold antennas around an airplane's fuselage, making for more precise radar. Now researchers at the University of ­Wisconsin-­Madison have made ultrathin silicon transistors that are 50 times as fast as their predecessors.

Previously, researchers at the University of Illinois at Urbana-­Champaign showed that ­nanometer-­thin films of single-crystal silicon transistors could be made flexi­ble. But Wisconsin researchers ­Zhenqiang Ma, professor of electrical and computer engineering, and Max Lagally, professor of materials science and physics, improved the transistors' performance by putting strain on the silicon's crystalline structure, increasing electron mobility. And by altering fabrication methods to reduce electrical resistance, Ma achieved a transistor speed of 7.8 gigahertz--fast enough for, say, a flexible sensor that could send and receive Wi-Fi signals. Ma says he expects to reach speeds of 20 gigahertz; military antennas are a likely first application.