Researchers ready radio-receiver-on-a-chip

By Eric Smalley, Technology Research News

Cornell University researchers have used a scanning tunneling microscope tip to make a tiny silicon rod vibrate at specific frequencies, creating a tunable micromechanical oscillator.

The rod is fixed at one end to form a cantilever that is 200 microns long and half a micron thick. A micron is one thousandth of a millimeter. When the tip of a scanning tunneling microscope touches different points on the cantilever it resonates at different frequencies. The effect is similar to pressing a vibrating string on a musical instrument in order to play different notes.

The Cornell oscillator varied in frequency by 300 percent, according to Maxim Zalalutdinov, a postdoctoral researcher at the university.

Tunable oscillators are the key component of radio receivers because they can zero in on different frequencies of radio waves. They are also used to focus sensors and microscopes that use probes to sense changes in pressure or magnetism.

The researchers are aiming to replace the scanning tunneling microscope portion of the device with a microelectromechanical system (MEMS), he said. This will make it possible to include communications devices and sensors based on tunable oscillators on the growing list of devices that can be put on a computer chip.

Most tunable oscillators are made out of crystals like quartz. They can be tuned accurately but they are relatively large at about 10 millimeters, said Zalalutdinov. "One of our major goals is to [achieve] quality... comparable to the quartz devices," he said. "Then it would... have both high quality and very small dimensions."

Researchers who work with Magnetic Resonance Force Microscopes (MRFM) have expressed interest in the tunable micromechanical oscillator, said Zalalutdinov. The microscopes are are essentially miniature Magnetic Resonance Imaging (MRI) machines for making 3-D images of microscopic objects. MRFM's have the potential to make detailed images of individual molecules within substances. MRFM’s today use MEMS-based fixed-frequency oscillators.

A frequency-tunable micromechanical oscillator could be implemented in a MEMS device in about two years, according to Zalalutdinov.

Zalalutdinov's colleagues were B. Ilic, D. Czaplewski, Alan Zehnder, Harold G. Craighead and Jeevak M. Parpia. They published their work in the November 13, 2000 issue of the journal Applied Physics Letters. The research was funded by the National Science Foundation.

Timeline:   2 years
Funding:   Government
TRN Categories:   MicroElectroMechanical Systems (MEMS)
Story Type:   News
Related Elements:   Technical paper "Frequency-tunable micromechanical oscillator" in November 13, 2000 Applied Physics Letters


November 29, 2000

Page One

Molecular motor shifts speeds

Virtual mic carries concert hall sound over 'net

Researchers ready radio-receiver-on-a-chip

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Crystal forms gas-triggered switch


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