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Sampling 'Small Atmospheres' In The Tiny New Worlds Of MEMS
Albuquerque NM (SPX) Mar 09, 2005 Just as astronomers want to understand the atmospheres of planets and moons, so engineers want atmospheric knowledge of worlds they create that are the size of pinheads, their "skies" capped by tiny glass bubbles. Should their silicon inhabitants - microcircuits, microgears, and micropower drivers - exist in a vacuum? An atmosphere of nitrogen? Air as we know it? More importantly, whatever atmosphere was intended, how long will it stay that way? Is the protective barrier hermetic or will its atmosphere change over time, potentially leading to the early death of the device? Will water vapor seep in, its sticky molecules causing unpredictable behavior? What, in short, can we say about how long this little world and its inhabitants will survive and function? The most advanced sampling procedure known - requiring only picoliters of gas to evaluate the contents of these small atmospheres - is now in place at Sandia National Laboratories, a National Nuclear Security Administration facility. The method was recently revealed at the SPIE Photonics Meeting in San Jose, Calif. "I know of no one, anywhere else, who can do this kind of testing," says Sandia innovator Steve Thornberg. John Maciel agrees. Chief Operating Officer of Radant MEMS, a three-year-old start-up company in Stow, Mass., he is under contract with DARPA to develop high-reliability MEMS (microelectromechanical) switches for microwave devices and phased array antennas. He also sees markets for his MEMS switches in cell phones. For long-term reliability, small-atmosphere stability is a must. "We can't go to a commercial house to get this work done," he says. "We can't find the capability anywhere else but Sandia." The Sandia method - funded by its Laboratory-Directed Research and Development program, and presented for consideration to Sandia's patent office - involves a small commercial valve that comes down like a trash compactor and crushes a tiny device until it releases its gases - currently, about 30 nanoliters - into a custom-built intake manifold. Because Thornberg's test mechanism requires only picoliters, his sensitive device can recheck its own measurements - using bursts of gas delivered in a series of puffs - dozens of times from the same crushed device in a 20-minute time span.
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