New device consists of a tiny, tunable silicon beam, could replace complex circuits, save power

As the wireless airspace gets more crowdedinterference concerns become much more pronounced.  Indeed, while hard numbers are hard to come by, it is thought that much of dropped calls and slow data traffic is attributable to interference in cases where lack of coverage is not the issue.

All electronics devices incorporate some degree of filtering to deal with interference noise from other frequencies on a certain frequency band.

Purdue University researchers are working on making a superior type of filter, replacing the traditional digital filters made of transistors, inductors, and capacitors.  The replacement uses a tiny mechanical part -- sometimes referred to as a nanoelectromechanical system (NEMS).

The NEMS device is created using silicon-on-insulator (SOI) -- a standard production process compatible with complementary metal–oxide–semiconductor technology (CMOS).  T filter made by the Purdue team is a tiny silicon beam that is 2 microns (2 um) wide and 130 nm thick (about 1,000th the width of a human hair).

NEMS device
The NEMS device filters signals, and can also be used to measure mass. [Image Source: Purdue]

When exposed to voltage, the beam vibrates up-and-down or side-to-side, like a jump rope.  The resulting device acts as a filter, accepting alternating current and outputting a pure filtered signal, based on the natural resonant frequency.

A big perk is that the simple process used to produce the NEMS has near 100 percent yields.  

Comments Jeffrey Rhoads, an associate professor of mechanical engineering at Purdue, "There is not enough radio spectrum to account for everybody's handheld portable device.  We are not inventing a new technology, we are making them using a process that's amenable to large-scale fabrication, which overcomes one of the biggest obstacles to the widespread commercial use of these devices.  Because of manufacturing differences, no two nanoscale devices perform the same rolling off of the assembly line.  You must be able to tune them after processing, which we can do with these devices."

Saeed Mohammadi, an associate professor of electrical and computer engineering at Purdue who co-authored the work, comments, "A vivid example [of the use of NEMS] is a tunable filter.  It is very difficult to make a good tunable filter with transistors, inductors and other electronic components, but a simple nanomechanical resonator can do the job with much better performance and at a fraction of the power."

"Because the devices are tiny and the fabrication has almost a 100 percent yield, we can pack millions of these devices in a small chip if we need to.  It's too early to know exactly how these will find application in computing, but since we can make these tiny mechanical devices as easily as transistors, we should be able to mix and match them with each other and also with transistors in order to achieve specific functions. Not only can you put them side-by-side with standard computer and electronic chips, but they tend to work with near 100 percent reliability."

Purdue NEMS
The new NEMS device is produced using traditional SOI, at near 100 percent yields.
[Image Source: Purdue]

The beam could also be used as a sensor to detect minute masses.  Professor Rhoads remarks, "The smaller your system, the smaller the mass you can measure.  Most of the field-deployable sensors we've seen in the past have been based on microscale technologies, so this would be hundreds or thousands of times smaller, meaning we should eventually be able to measure things that much smaller."

A study on the work was published [abstract] in the peer-reviewed journal IEEE Transactions on Nanotechnology.

Professor Mohammadi is the senior author of the work, while Lin Yu -- a Ph.D recipient in physics from Purdue -- is listed as the first author.  The research was funded by grants from the National Science Foundation.

Sources: Purdue, IEEE Explore

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