Y. expert shrinks switches

Remember when cell phones were the size of a brick?

Not that you owned one.

Back then, in the early '90s, cell phones were clunky and the domain of the rich and famous.

Now almost everyone has one. And they seem to get smaller every year.

A Brigham Young University professor has found a way to make them even smaller, but there is one little problem — the switches sometimes get stuck.

Through a new technology not yet available in commercial products, mechanical engineering professor Brian Jensen says he has found a way to make batteries last longer for electronic devices like cell phones and laptop computers.

The solution, Jensen says, is tiny electrical switches.

In the same way a light switch routes a signal to turn a light bulb on or off, tiny switches can be used to send the electrical signals that make battery-powered devices work.

The switches (categorized as micro-electro mechanical systems, or MEMS) are made of two minuscule pieces of metal that transmit signals when pushed together. MEMS switches are roughly the size of a human hair and move back and forth more than 1,000 times a second.

"They would mostly be used in communications devices, like a cell phone, where you'd want them to be able to switch a signal back and forth between different parts of a circuit very rapidly," said Jensen, explaining that cell phones use one antenna to both transmit and receive signals. "A system that used MEMS switches could feasibly route those signals with lower power loss and reduce the number of electrical components needed to make the phone work."

The new technology could also help improve communications on military aircraft, Jensen says.

Fighter jets currently use multiple antennas to keep communication lines open.

But by using MEMS switches a single antenna could operate on multiple frequency bands. The switches could turn on and off different parts of an antenna, allowing it to send and receive at multiple frequencies.

Fewer antennas on an aircraft would save money, weight and space, Jensen said, and help keep communications secure. If one frequency is jammed, the antenna could operate on another.

The only problem with MEMS switches is that they sometimes stick.

"Sometimes when the switches close and current runs through them, they stick," Jensen said. "Some we've tested take almost a full second to open, and that's just not good enough."

So Jensen and a group of researchers at the University of Michigan recently did a study to learn what made the tiny switches stick. They also wanted to know how to make them move faster on a consistent basis.

They found that the smaller the contact area between the metal pieces that comprise the switch, the less it sticks.

"Common sense would tell you to make that area as big as you can to get more signals across it," Jensen said. "But the smaller the area, the less the switch sticks."

Jensen's study was published in the June 15 issue of the "Journal of Applied Physics."

"A popular question right now is, 'Are we at the frontier of battery technology?' Battery life is what it is at the moment, and if we can find ways for these devices to lose less power, we can make them last longer."

Jensen says MEMS switches could be used in cell phones within two to three years.

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E-mail: jhyde@desnews.com