Military Invests In Microelectronic Machine Technology

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March 21, 1998 (8:53 AM EST)

Military Invests In Microelectronic Machine Technology

ARLINGTON, Va. -- For developers of the next generation of military and space technology, big things may be coming in small packages.

Technologists from the Defense Department, NASA, and other government agencies touted the promise of emerging microelectronic machines (Mems) at a government microsystems conference here in Arlington, Va., last week. Planners envision kilogram-scale aircraft, "nanosatellites," and other pint-sized systems that could integrate key subsystems such as avionics on a single chip and maneuver into orbit using microthrusters.

On the commercial side, the machines could usher in the era of Dick Tracy-style wireless wrist communicators as the technology replaces the bulkiest of cell-phone components such as passive discrete devices, proponents said. Extreme miniaturization capabilities offered by Mems could yield the next generation of low-power communications, said Albert Pisano, Mems program manager at the Defense Advanced Research Projects Agency (Darpa).

Darpa spent more than $134 million over the past two years on Mems research, and is seeking another $71.5 million in fiscal 1999 as it looks to develop what the agency calls "advanced microsystems." Among the enabling technologies being investigated are wireless communicators, networks of tiny sensors and actuators, and a system that integrates airborne sensors and communications.

Darpa's growing interest in Mems stems from the technology's ability to combine sensing, computing, and actuating capabilities on a single small device. In one possible military application called "active conformable surfaces," sensors and actuators embedded in the skins of aircraft could change the shape of a delta wing much as a bird's wing changes shape during flight, Pisano said.

Examples like this are why experts call Mems a "surface technology" that can be used nearly everywhere, since micromachines based on chip-fabrication techniques don't require the packaging that integrated circuits (ICs) need.

Darpa also foresees using Mems for applications such as inertial navigation units on a chip, electromechanical signal processing, unattended sensors, weapons fusing, and mass-storage devices.

Accelerometers appear to be an early candidate for both commercial and military use. Analog Devices, in Norwood, Mass., said it plans to demonstrate in May a motion-sensing device for computer games. The chip maker shipped the first surface-micromachined accelerometer, the ADXL50, in 1993. The device includes on-chip signal conditioning.

Experts at the conference agreed that Mems is poised to take off. "It's an extremely broad field," said William Trimmer, president of Belle Mead Research, a New Jersey consultancy. He said Mems technology is potentially very inexpensive.

Cost and size advantages are the primary reasons why the Defense Department, NASA, and other agencies accustomed to building big-ticket items, often well over budget, are attracted. NASA administrator Daniel Goldin told the conference attendees miniaturization has helped revive U.S. space exploration. After launching just two large interplanetary probes in the 1980s, Goldin said NASA has more than 30 space probes in the works. The Mars Pathfinder probe relied heavily on miniaturization and off-the-shelf electronics, he said.

Goldin said spacecraft designers will make use of microelectronics and Mems technology to shrink future probes to the size of a television set or smaller. Future "nanospacecraft" will integrate key functions such as avionics on a single chip, Goldin said he predicted.

Researchers envision even smaller nanosatellites in the 1-to-10-kilogram range using microthrusters to maneuver. Clusters of these low-earth-orbit nanosats could be used for communications and Earth-observation missions, according to researchers from Los Angeles-based Aerospace.

Ultimately, the company said it hopes to use a manufacturing technique called batch fabrication to build entire spacecraft on thick silicon wafers. The nanosats would consist of less than 50 individual micromachined parts. Constellations of the nanosats would be equipped with microthrusters to boost them into orbit and keep them there.

Aerospace is pursuing batch fabrication of several types of microthrusters, including "resistojets" that use standard IC and Mems fabrication techniques and "micro-hollow-cathode" thrusters. Hollow cathodes are key components of impulse thrusters on ion engines. Conventional ion engines are already being used to keep geostationary satellites in orbit.

Meanwhile, military laboratories are investigating whether Mems can be used in airborne radar, communications, and electronic warfare systems. The Air Force Research Laboratory is developing micro- and millimeter-wave switches based on Mems for phased-array transmit/receive modules.

Researchers reported at the conference that Mems provide a significant reduction in phase-shifter insertion loss from 6 dB to 0.5 dB. They also reduced manufacturing costs by boosting chip yields by 65 percent.