The research could lead to simple detectors capable of differentiating between a wide variety of pathogens,i ncluding viruses, bacteria and toxic organic chemicals.

The experiment, an extension of earlier work in which similar devices were used to detect the mass of a single bacterium, is reported in a paper, "Virus detection using nanoelectromechanical devices," in the September 27, 2004, issue ofApplied Physics Letters by Cornell research associate Rob Ilic of the Cornell NanoScale Facility (CNF), Yanou Yang, a Cornell graduate student in biomedical engineering, and Harold Craighead, Cornell professor of applied and engineering physics. The work was done with the assistance of Michael Shuler, Cornell professor of chemical and biological engineering, and microbiologist Gary Blissard of the Boyce Thompson Institute for Plant Research on the Cornell campus.

At CNF, the researchers created arrays of tiny silicon paddles from 6 to 10 micrometers (millionths of a meter) long, half a micrometer wide, and about 150 nanometers (billionths of a meter) thick, with a one-micrometer square pad at the end. Think of a tiny fly-swatter mounted by its handle like a diving board. A large array of paddles were mounted on a piezoelectric crystal that can be made to vibrate at frequencies on the order of 5 to 10 megaHertz (mHz). The experimenters then varied the frequency of vibration of the crystal. When it matched the paddles' resonant frequency, the paddles began to vibrate, as measured by focusing a laser on the paddles and noting the change in reflected light, a process called optical interferometry.

The natural resonant frequency at which something vibrates depends on, among other things, its mass. A
'"/>

Contact: Bill Steele
ws21@cornell.edu
607-255-7164
Cornell University News Service
4-Nov-2004