TINY 'MEMS' DEVICES TO FILTER, AMPLIFY ELECTRONIC SIGNALS

Researchers are developing a new class of tiny mechanical devices containing vibrating,
hair-thin structures that could be used to filter electronic signals in cell phones and
for other more exotic applications.

Because the devices, called resonators, vibrate in specific patterns, they are able to cancel
out signals having certain frequencies and allow others to pass. The result is a new type of
"band-pass" filter, a component commonly used in electronics to permit some signals to pass
through a cell phone's circuitry while blocking others, said Jeffrey Rhoads, an assistant
 professor of mechanical engineering at Purdue University.

Such filters are critical for cell phones and other portable electronics because they allow
devices to process signals with minimal interference and maximum transmission efficiency. The
new technology represents a potential way to further miniaturize band-pass filters while
improving their performance and reducing power use, Rhoads said.

The device is an example of a microelectromechanical system, or a MEMS, which contain tiny
moving parts. Incoming signals generate voltage that produces an electrostatic force, causing
the MEMS filters to vibrate.

Researchers have proposed linking tiny beams in straight chains, but Rhoads has pursued a
different approach, arranging the structures in rings and other shapes, or "non-traditional
 coupling arrangements." One prototype, which resembles spokes attached to a wheel's hub, is
about 160 microns in diameter, or comparable in size to a grain of sand.

Findings are detailed in a research paper to be presented on Sept. 2 during a meeting of the
American Society of Mechanical Engineers' Third International Conference on Micro and Nano
 Systems. The conference runs from Aug. 30 to Sept. 2 in San Diego. The paper was written by
 Rhoads and mechanical engineering graduate student Venkata Bharadwaj Chivukula.

In addition to their use as future cell phone filters, such resonators also could be used for
advanced chemical and biological sensors in medical and homeland-defense applications and
 possibly for a new type of "mechanical memory element" that harnesses vibration patterns to store information.

"The potential computer-memory application is the most long term and challenging," Rhoads said.
"We are talking about the possibility of creating complex behaviors out of relatively simple
substructures, similar to how in cellular biology you can have a relatively complex behavior by
combining hundreds or thousands of simple cells."

The band-pass filter design promises higher performance than previous MEMS technology because
 it more sharply defines which frequencies can pass and which are rejected. The new design also
 might be more robust than the traditional linear arrangement, meaning devices could contain
manufacturing flaws and still perform well.

The devices are made of silicon and are manufactured using a "silicon-on-insulator" procedure
 commonly used in the electronics industry to make computer chips and electronic circuits. The
 small, vibrating mechanical structures contain beams about 10 microns in diameter, which is
 roughly one-tenth the width of a human hair. The beams can be connected mechanically, like
tiny springs, or they can be linked using electric fields and magnetic attractions.

Raiza Pernia
CI. V-17.528.555
CRF

http://www.scitech-news.com/2009/08/tiny-mems-devices-to-filter-amplify.html