Now, by "playing" a new, streamlined nanoguitar, Cornell physicists are demonstrating how such devices could substitute for electronic circuit components to make circuits smaller, cheaper and more energy-efficient.
Lidija Sekaric, who built the new, playable nanoguitar while an Applied Physics graduate student at Cornell, described the project, along with other materials and device research in nanoelectromechanical systems (NEMS), at the 50th International Symposium and Exhibition of the American Vacuum Society, Nov. 2 to 7 in Baltimore,. At the same meeting Harold Craighead, professor of applied and engineering physics at Cornell, presented a plenary talk reviewing the uses of NEMS in biology. Sekaric worked in the Craighead Research Group at Cornell, part of the Cornell Center for Materials Research study of NEMS systems.
NEMS usually refers to devices about two orders of magnitude smaller than MEMS (microelectromechanical systems). Craighead prefers to define NEMS as devices in which the small size is essential for the job, such as those that respond to very small forces or biosensors so small that they can measure the mass of a single bacterium.
Sekaric, now a researcher at IBM's Watson Research Center in Yorktown Heights, N.Y., worked with Cornell graduate student Keith Aubin and undergraduate researcher Jingqing Huang on the new nanoguitar, which is about five times larger than the original, but still so small that its shape can only be seen in a microscope. Its strings are really silicon bars, 150 by 200 nanometers in cross-section and ranging from 6 to 12 micrometers in length (a micrometer is one-millionth of a meter; a nanometer is a billionth of a meter, the length of three silicon atoms in a row). The strings vibrate at frequencies 17 octaves higher than those of a real guitar, or about 130,000 times higher.
"The generations of researchers to come can aim to play more complex pieces," says Sekaric. "This goal would indeed improve the science and technology of NEMS by aiming for integrated driving and detection schemes as well as a wide range of frequencies produced from a small set of vibrating elements."
Most of the devices the group studies don't resemble guitars, but the study of resonances often leads to musical analogies, and the natural designs of the small resonant systems often leads to shapes that look like harps, xylophones or drums. The guitar shape was, Craighead says, "an artistic expression by the engineering students." Sekaric notes that "a nanoguitar, as something close to almost everybody's understanding and experience, can also be used as a good educational tool about the field of nanotechnology, which indeed needs much public education and outreach."
The ability to make tiny things vibrate at very high frequencies offers many potential applications in electronics. From guitar strings on down, the frequency at which an object vibrates depends on its mass and dimensions. Nanoscale objects can be made to vibrate at radio frequencies (up to hundreds of megaHertz) and so can substitute for other components in electronic circuits. Cell phones and other wireless devices, for example, usually use the oscillations of a quartz crystal to generate the carrier wave on which they transmit or to tune in an incoming signal. A tiny vibrating nanorod might do the same job in vastly less space, while drawing only milliwatts of power.
|For laboratory NEMS research, Cornell physicists use less musical devices like this nanopaddle, which can be set into motion by laser light. <|
As the nanoguitar shows, NEMS can be used to modulate light, meaning they might be used in fiber-optic communications systems. Such systems currently require a laser at each end for two-way communication. Instead, Craighead suggests that a powerful laser at one end could send a beam that would be modulated and reflected back by a far less expensive NEMS device. This could make it more economical to run fiber-optic connections to private homes or to desktop computers in an office.
Current research at Cornell, Craighead says, still focuses on understanding what materials work best for making NEMS, how such small devices work and what they can do, gathering understanding that can be used in building future applications. .
The Craighead Group NEMS research also includes graduate students Rob Reichenbach and Scott Verberage, research associate Maxim Zalalutdinov and Physics Professror Jeevak Parpia. Aubin, Reichenbach and Zalalutdinov recently received the 2003 Collegiate Inventors Prize for an ultra-small oscillator.
Related World Wide Web sites: The following sites provide additional information on this news release.
The original nanoguitar story: http://www.news.cornell.edu/releases/July97/guitar.ltb.html
Craighead Research Group: http://www.hgc.cornell.edu/index.html