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Nanoguitar Rocks World of the Small

By Pippa Wysong, Access Excellence


Ithaca, NY (12/31/03)- Researchers have built a guitar about the size of a red blood cell, and can play it too.

The nanoguitar is only a sampling of the research coming out of Cornell University where a mix of physicists, engineers and biologists are studying the characteristics of nanoelectromechanical systems (NEMS) and their potential applications.

The guitar demonstrates a number of features unique to the world of the very small which could prove useful to applications of the technology in the future, said Lidija Sekaric, PhD. She was part of a team that built the nanoguitar when she was a gradtuate student in applied physics at Cornell University.

Objects this small behave differently than structures built on a larger scale, and so have novel features that may be useful in electronics, chemical and bio-sensors, and other areas.

"Most of my time in graduate school was spent studying mesoscopic physicis," she said. This is an area that hovers between the study of the truly small such as individual atoms, and macroscopic physics.

"We're looking at something in between aggregates of hundreds of atoms or so across, like these (nanoguitar) structures are. We're asking how does matter behave at that size scale?" she said.

The minute guitar is made of silicon crystal and was carved out using a technique called electron-beam lithography. The material and the technique are both used in the production of computer chips.

The nanoguitar, which was modeled after the Gibson Flying V, was made for educational purposes to demonstrate the current state of nanotechnology. It is 40 microns in length, and is 20 times larger than a nanoguitar made in the same research lab seven years ago. The earlier guitar resembled the Fender Stratocaster, but lacked easily playable strings.

The newer guitar can be played, though not in the traditional sense of plucking strings. The carved-out strings range from 6 to 12 micrometers in length and vibrate at frequenecies 17 octaves higher (at a pitch 130,000 times higher) than those of a real guitar. To play the nanoguitar, researchers use targeted laser-light. The light hits the strings causing them to oscillate which creates interference patterns in the light reflected back. This pattern is detected and electronically converted down to audible notes.

The fact that parts of nanostructures can be made to vibrate is a feature that could prove useful in a number of potential applications in engineering, biology and science. For instance, in another nanotechnology research project, Cornell researchers attached a single E. coli bacterium to a nanostructure the shape of a diving-board.

"When you vibrate the diving-board before and after the bacterium is attached, there's a change in the natural frequency of vibration because the mass of the board has changed," Dr. Sekaric said.

With very small objects like this, "you increase their resonant frequency but decrease their mass. Very small additions of mass (such as the E. coli) will cause a large shift in frequency," she said. This feature could be used in mass sensors designed to detect small amounts of chemicals or contaminants.

In another direction, "if you can generate a sustained frequency that can be picked up by something in the RF (radiofrequency) range, then you could maybe replace some small parts in cells phones that are fairly large, have low yield and use up more power," she said.

The properties of matter change and things behave different in the world of the very small.

"Why do we want to go small? Because something changes. It makes you able to so something you weren't able to do with a large scale system," Dr. Sekaric said.

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