MEMS vs. nanotubes: Cell phones could use both

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Oct. 22, 2003 – Can a nanotube boldly go where no MEMS have gone before — or at least share a ride to the destination?

Two researchers at the University of California, Irvine, are using a $300,000 grant from the Defense Advanced Research Projects Agency to develop radio frequency signal processing components for wireless communication based on carbon nanotubes. Peter Burke and William Tang’s research could lead to a mobile phone with its electronic and mechanical functions on a single chip — saving power, space and cost.

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One-chip integration also is a goal sought by nano’s next of kin. MEMS researchers are a little ahead in development, but a commercial solution remains years off for either camp.

“With DARPA, they like to fund some projects that are risky — (this is) more risky than MEMS,” said Burke, an assistant professor of electrical engineering and computer science. Burke leads the university’s nanotechnology group. He also is affiliated with the California Institute for Telecommunications and Information Technology, a publicly and privately funded group that links faculty, students, research professionals and industrial partners on interdisciplinary projects.

“Both have technical challenges, both have potential advantages. I think at this point, both are potentially valid solutions.”

Of course, working with Tang doesn’t hurt nano’s chances, according to Burke. Tang, a professor of biomedical and electrical engineering, is a former MEMS program manager for DARPA. “He is really up-to-date on what all the differences are, on both the device and system level,” Burke said.

Burke and Tang are starting with the filter, which selects the proper frequency among many conversations being broadcast and presents it to the rest of the phone’s electronics. It might seem like a trivial piece, Burke said, given all the other functions of a phone, but they determined it would be the best — not the easiest — place to start.

“One of the key technical hurdles is the filter,” Burke said. “Currently it’s a separate chip for that one specific function. … Having one chip for one function adds cost.”

Ann Arbor, Mich.-based Discera Inc. was founded in 2001 with a one-chip solution in mind. It plans to pursue filters based on its microresonator technology, but its first order of business is a MEMS-based oscillator to generate radio waves for communication.

The company began sampling the MRO-100T micro-oscillator in June. Discera’s lead investor is Ardesta LLC, parent company of Small Times Media.

Also making strides in reducing size inside the phone is Agilent Technologies. Its MEMS-based miniature film bulk acoustic resonator duplexer, the device that allows two-way conversation, is as much as 80 percent smaller than traditional duplexers, according to the company. 

Even as it ships about 2 million duplexers a month, Agilent has developed a 66 percent smaller version: It’s selling samples to select manufacturers and expects broad market availability by January. The new version has enabled Agilent to integrate filters, power amplifiers and other components into a complete front-end module.

“More than anything, it provides a real estate savings — there’s room for cameras, multimedia capability,” said Philip Gadd, worldwide marketing manager of Agilent’s Wireless Semiconductor Division. “We’re taking the discrete parts we would have sold to them and replacing them with one package.”

MEMS developers primarily look at mechanical approaches, while Burke and Tang are looking at the electronic properties of nanotubes. Burke said electrons can move in nanotubes without scattering, which minimizes energy loss.

Burke and Tang hope to have a prototype within two years, and commercialization is possible a couple of years beyond that. Once a prototype has been demonstrated, Burke said, he’s open to the idea of merging micro and nano approaches — such as using nanotubes as mechanical, vibrating objects.

“MEMS and nanotube electronics are competing, but it’s also possible to merge the advantage of both technologies into one device,” he said.

“That may be the best long-term solution.”


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