Listening Large: E-Textiles For Battlefield Sound Detection Begin Field Tests This Year

September 5, 2002

For decades, electronics have been getting smaller and smaller. Now, engineers are turning to one of mankind's oldest arts -- weaving -- for a cost-effective way of making certain devices bigger and bigger.

The STRETCH program is a cooperative venture between the University of Southern California and Virginia Tech that is now testing a prototype "e-textile" — a special cloth interwoven with microelectronic components.

The cloth functions as a supersensitive detection array to pinpoint sources of faint sounds, specifically, the sounds of distant vehicles moving on future battlefields. According to its creators, STRETCH is the first time an e-textile has been produced that can perform all aspects of such a complicated process.

"Modern methods of making fabrics allow extraordinary control over materials and properties," says Robert Parker, director of the Arlington, Virginia campus of the USC School of Engineering's Information Sciences Institute, and co-principal investigator on STRETCH. "And cloth has properties that can be very useful for certain electronic applications. We can easily and cheaply make very large pieces of cloth, light and very strong, that can be stretched over frames into any desired shape."

The material Parker and his co-investigator, Mark Jones of the Configurable Computing Laboratory at Virginia Polytechnic Institute and State University in Blacksburg, VA, have created could be deployed in various ways: as a parachute, a tent, a camouflage net, a sail, or simply as a bolt of cloth rolled compactly away until needed.

However deployed, the idea is the same, they say. Modern methods of detection use arrays of individual detectors, arranged in a pattern, and combine the reports from all into a detailed image using sophisticated computational algorithms.

Parker and his ISI colleagues have long been working on arrays made up of small, standalone detectors that are individually placed in the environment, and communicate with each other by radio.

But embedding similar units into fabric has advantages, according to Parker. "The signals they exchange can be carried on wires in the fabric. This greatly lowers the power requirements to operate the system."

Additionally, signal exchanges by radio can potentially be picked up by an adversary, giving away not only the fact that surveillance is underway, but also the position of the surveillors — a potentially fatal drawback in modern battlefield conditions.

"Forming it into a fabric makes it electronically silent." says Jones. Additionally, while embedding the detectors in fabric sacrifices the flexibility of individual standalone units, it ensures the units will be automatically be in the right positions relative to each other to do their jobs optimally.

The STRETCH fabric will begin testing in field environments in November. Many problems have to be resolved. As Parker notes, "while fabric manufacturing technology is advanced, we expect that the large number of components and the inherent imprecision in the process will make it difficult to weave very large, fault-free arrays."

Making these tough enough to stand up to weather and rough handling in field conditions is another challenge.

However, in preliminary tests, the material has proven robust. It can be rolled (though not folded) and unrolled, without damage. And even when numbers of the individual units fail, the detector is still able to function effectively.

Will soldiers' wardrobes someday include sound detector sweaters, satellite signal antenna hats, or chemical sniffer vests? Not right away — but perhaps soon.

"Existing prototype fabrics have discrete electronics attached after the normal weaving process," explained Parker, "but the goal is to eventually produce individual yarns that provide an electronic function such as a battery power source or a transistor array; a sensor of environmental conditions such as temperature, pollutants, airborne toxins, or communications; or an actuator such as a synthetic muscle.

"These yarns are conceived to be very thin and flexible and able to be woven into the cloth on a loom in a standard high-volume cloth manufacturing process. The type of fabric chosen would be determined by the final use of the fabric and could vary from cottons used for blouses or shirts to heavy canvas or Kevlar used heavy-duty applications.

"Although early work focuses on acoustic sensing, think of future wearable fabrics with integrated cell phones, navigation systems, or personal warning systems."

Parker concluded with a vision reminiscent of the recent film Minority Report:

"Think of your blouse or slacks "interacting" with the environment as you pass through it. Think of walking into a mall and your blouse tells you where you can get that special gift item that has been on your "must get" list for months.... or maybe it reminds you that you should hit the gym to shed those couple pounds that the holiday season accumulated."

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The Defense Advance Research Projects Agency (DARPA) funded STRETCH. In addition to Parker and Jones the research group includes Ron Riley at USC/ISI and Don Leo, Louis Beex and Zahi Nakad at Virginia Tech/CCL.

Part of the US News & World Report 8th-ranked USC School of Engineering, the USC Information Sciences Institute is one of the nation's leading computer science research and development centers, with a broad research program in artificial intelligence, networking and communications, software generation, integrated circuits and microdevice fabrication, parallel and distributed computing. ISI, with a staff of 350, has two research locations, the main facility in Marina del Rey, California, and an East Coast facility in Arlington, Virginia.

Virginia Tech is the home of the Commonwealth's leading College of Engineering. U.S. News & World Report, in its "America's Best Graduate Schools 2003" survey, released in April 2002, ranked the College's graduate program 23rd. The College was rated 15th in the nation by corporate recruiters and 18th by engineering school deans, and the deans ranked five of the College's graduate programs among the top 25 in their fields. The electrical and computer engineering department was ranked 21st. In its undergraduate school survey, ECE was ranked 16th.

Note: STRETCH is not an acronym; the initial letters do not stand for anything; it is simply the name of the project.