01 August 2003
Textiles fight back in the U.S.
Going to the front with wearable computers.
By Ellen Fussell
Electronic textiles (e-textiles) are fabrics with electronics and interconnections woven into them. According to the Virginia Tech e-textiles group (www.ccm.ece.vt.edu), "components and interconnections are intrinsic to the fabric and thus are less visible and not susceptible to becoming tangled together or snagged by the surroundings." E-textiles can adapt to changes in the computational and sensing requirements of applications. Wearable computing and large-scale sensor networks are two main e-textile applications. Wearable computers can sense motion and know what objects surround the user. Sensor networks are more applicable in harsh environments. They also need to be very low power and able to last days and weeks in the field without maintenance.
Military research is finding materials to sense chemicals in the air or respond to radioactivity. Researchers are looking for textiles that can be a canvas for a truck and an antenna that sends and receives messages and radio waves. E-textiles are giving firefighters the ability to sense their way through burning buildings. "The most extensive uses will be in industrial applications in which wearable computers can display schematics for construction and maintenance workers, freeing their hands for tasks," said Virginia Tech's Electrical & Computer Engineering ECE Connection article, "Department researchers design e-textiles for computerized clothing & military applications." Virginia Tech research-ers are looking into ways to tailor sensors and processing elements to fit the needs of today's users.
The ability to sense, respond, and adjust to stimuli such as pressure, temperature, or electrical charge is an exciting new field for manufacturers too. Textile engineers, computer scientists, and electrical engineers may one day be able to combine electronics and textile structures to come up with new lightweight and flexible products that manufacturers can make as fast as today's traditional textiles. They might one day be using a flexible, foldable computer keyboard, according to Textiles Industries Media Group (www.textileindustries.com). Some say electrotextile products will show up in new markets—healthcare, entertainment, safety, homeland security, computation, communication, thermal, protective clothing, or even energy harvesting from tensioned structures and other large-area fabrics.
Woven fabric structures can also provide a complex network of elaborate electric circuits with electrically conducting and nonconducting constituents, according to Textiles Industries Media Group's Web site. Its structure allows multiple layers and spaces to accommodate electronic devices. Rigid printed circuit boards have wiring layers separated by insulating layers with vias connecting power, ground lines, and wiring of different layers to process and transfer signals. These boards, fabricated using slow photolithography, will soon be defunct, replaced with flexible, stitched, multilayered woven fabric structures manufacturers will be able to produce at speeds of 40 to 100 square meters per hour, depending on weaving speed, pick density, and weaving-machine width. Today, commercial electrically conducting yarns made from metals or polymers coated with metals include short-staple and continuous-filament steel yarns, copper yarns, and silver-coated nylon yarns, according to the site. Thin fibers or filaments make up these yarns, which makes them feel and behave like textile yarns.
COMMUNICATE AND INSULATE
Weaving technology into tradition
"All these are new ways textiles are growing in the high-tech area. But at the same time, companies like Milliken & Co., Unifi, and others are fighting to hold on to and grow their share of traditional textiles, because in countries like Guatemala people make about $4 a day for a twelve-hour day, and they're thankful for the job," said Jon Rust, professor of textile engineering and associate department head of Textile Engineering Chemistry and Science at NCSU in Raleigh, N.C.
Rust said this means people in the U.S. can often buy textiles from a company with manufacturing facilities in low-wage countries more cheaply than from domestic companies.
Yarn is one product that is actually doing well in the U.S., especially in companies such as National Textiles and Frontier Spinning. That is because the U.S. is the world's largest cotton producer, Rust said. "We have the raw material here. Technology is advanced in cotton; it's a capital-intensive business rather than a labor-intensive business." So with a few people, the company can make millions of pounds of yarn every week and be close to the source of raw material—the cotton field.
Companies like Milliken not only make their own yarn, but they also weave it, dye it, and finish it. Then the company sells it to people who cut and sew and make the goods. "Often times in Third World countries, in addition to low wages, the environmental laws are more lax," Rust said. "But here the water that leaves your plant has to be cleaner than it was when it left the river. It makes competing with people in those areas very difficult."
By including communications within what you are wearing rather than carrying radios that sense the environment you are in—that is where the value comes in. "If you're a firefighter going into a chemical fire, you have to worry about smoke as well as chemical and thermal threats. If you can monitor the environment as you go in and have that automatically fed back to your commander, the people in control can know what's going on, and they can map it over the whole incident," he said. "You could also have alarms to know if you're getting a more intense thermal threat and if there are more materials coming into the environment that are more threatening."
The same goes in a manufacturing environment, "although you'd probably have more limited units—having detection sensors and locators," Thompson said. "If you're out in a unit and you have a sniffer that picks up a leak, then it could provide you with an alarm warning and notify people in control centers in the plant." A communication system in clothing with a microphone built into the collar would give responders the ability to communicate back to home base and vice versa. "If you're responding to a leak, the communications base could direct you with remote sensing to get to the right spot. They can say you need to be 15 meters to your right, and it's on the second level."
Although electronic clothing is being used now, a viable future in e-textiles would depend on the funding streams that come into the research, Thompson said. "Things get developed in NASA and the military, and because of all the work with first responders and the military, I think we'll see miniaturized locators and communication systems within the next five to ten years," he said. "Things like PDAs built into a wrist or into a pocket—there are a variety of thoughts about how you'd do that. While it might be reminiscent of the Dick Tracy comic, it's fast becoming more of a reality."
NONWOVENS ARE NOW
Quite a few of the components that go into chemical, biological, and thermal protection are nonwovens, Thompson said. Filter media (fibers that make up filters for air purifiers) play a large role in protecting workers from particulates or aerosols. "In a situation where you need to protect yourself from particulates or aerosols, you may be able to use air purifiers and respirators—maybe charged filter media like electret filters," Thompson said. Many companies, such as Home Depot, now make traditional filters that let air pass through them. This type of filter would be in air purifying masks if you had to work with dust or aerosols and protect yourself.
The most common technology is in mechanical filters that take stuff out of the air as you breathe through them. But with those, there is a high pressure drop, which means it is harder to breathe. However, if you use electret or other charged filters, they take the particles out by drawing them to the fiber surface through electrical charge so they don't have as much resistance from the air passing through them. "It gives workers a new way of protection with less difficulty in breathing so they can work longer and more comfortably," Thompson said.
While materials like gortex keep chemicals out, they are not really nonwovens. "It's an expanded film that's somewhat porous," Thompson said. "It lets moisture vapor through and keeps out liquid, so it's breathable to keep you dry and cool." But gortex does not work against a lot of chemicals. So there is a real opportunity to make nonwovens that keep out particles and aerosols and treat surfaces that will help prevent the passage of chemical and biological threats.
Because, according to Thompson, the U.S. leads the world in protective clothing and apparel, "we have the opportunity to sell both in our country and elsewhere. The use of protective clothing is important in all industries because you want people to be safe," he said. That would be true whether you are looking at a chemical uniform that is lightweight, a fire protective suit, or a protective suit for a hostile environment.
"You have to have those things to keep functioning and to be able to respond. While the textile industry is critical in its own right, it's also making other industries function better," he said. People who work on power lines have to wear protective clothing (for electric arc protection) to do their job. Foundry workers have to have protection from heat. Many industries rely on this field. And although the textile industry is an area rich in technical content, there are still more advances to be made. The area of protective clothing also protects part of the industry from foreign competition because it is not a routine, easily replicated technology. "There are a lot of details and certifications to pass, so you want to have high technology," Thompson said. "But the industry as a whole has great potential for growth." IT
Pyroman saves lives
Pyroman is a mannequin at NCSU in Raleigh, N.C., who takes the heat as researchers study the protective performance of full garments in a flash fire (when firefighters are engulfed in fire). "We have a well-controlled flash-fire system with 122 thermal sensors on the mannequin," said Don Thompson, NCSU's special projects director at the Center for Research on Textile Protection and Comfort. The sensors are evenly distributed around the body, legs, and back. "We calibrate it by burning the system nude so we know how each sensor is performing and the fire is well characterized." The clothing Pyroman tests includes industrial coveralls (as worn in chemical plants), military garments, firefighter turnout suits, and proximity suits for close-up fire fighting such as in an oil-fueled fire.
The NCSU research team also deals with transport movement of infectious agents and biological viruses and bacteria across membranes for medical applications—testing surgical gowns. "We do the same kind of testing for particulates for clean room applications," Thompson said. "For chemical plants we can test the integrity of these garments versus chemical agents."
Having a testing mannequin like Pyroman in a university is pretty unique, Thompson said. (DuPont has a similar system.) The university also tests on a sweating mannequin, which looks at how much heat and moisture can be transmitted through garments. These garments are heavy and highly encapsulating—keeping moisture in so firefighters maintain breatheability and avoid heat stress. "The balance is having something lightweight enough to move around in, but at the same time to protect you from these environments," Thompson said.