Posted in | Nanofabrication

Energized Fabrics Could Keep Soldiers Comfortable and Battle-Ready in Cold Climates

In arctic conditions, soldiering is extremely hard. Protective clothing can be heavy and can result in overheating and sweating upon exertion. In spite of wearing such gear, hands and feet can grow numb.

To ensure that military personnel are battle-ready and more comfortable in severely cold climates, Researchers are currently doing research in order to create high-tech fabrics that heat up when powered and that trap sweat. In future, these fabrics could even be used in consumer clothing.

High-tech fabric intended for gloves and other military clothing contains silver mesh (silver nanowires or 'AgNW') that could be heated to keep soldiers warm, while a hydrogel layer would absorb sweat. (Credit: US Army Natick Soldier Research Development and Engineering Center)

The Scientists are presenting the results of the study at the 254th National Meeting & Exposition of the American Chemical Society (ACS). ACS, the largest scientific society in the world, is conducting the meeting here until Thursday. It has approximately 9,400 presentations on a variety of science topics.

Most of the Army's cold-weather hand gear was designed more than three decades ago, so soldiers usually prefer to purchase winter gloves at retail stores, said Paola D'Angelo, Ph.D. However, even this modern gear is not sufficient to prevent paratroopers from losing feeling in their feet and hands while parachuting to earth in arctic conditions.

That's problematic if soldiers have to operate weapons as soon as they land. So we want to pursue this fundamental research to see if we can modify hand wear for that extreme cold weather.

Paola D'Angelo, Ph.D

The study was inspired by research headed by Yi Cui, Ph.D., at Stanford University. After synthesizing extremely fine silver nanowires, Cui’s team placed a network of the wires on cotton. The Researchers were able to heat the fabric by applying power to the silver nanowires.

D'Angelo, Elizabeth Hirst, Ph.D., and colleagues at the U.S. Army Natick Soldier Research, Development & Engineering Center, are trying to extend this silver nanowire idea to fabrics apt for military uniforms, such as polyester and a nylon/cotton blend. The Army team discovered that applying only 3 volts to 1 inch by 1 inch test swatches of these fabrics - the output of a normal watch battery - increases the temperature by 100 ºF in just a single minute.

If these experimental fabrics are eventually used in uniforms, soldiers can change the amount of heat generated by their uniforms by simply dialing up or down the voltage and thus match the weather conditions. The additional heating indicates that uniforms could be lighter and thinner which turns out to be an advantage for soldiers who should carry heavy loads and walk long distances.  

The Researchers are also integrating a layer of sweat-absorbing hydrogel particles that are made of poly(N-isopropylacrylamide) or polyethylene glycol. According to them, these particles might prevent other layers in the fabrics from getting wet, which, in turn, would keep the soldiers more comfortable during missions. Once the soldiers return to base, they can hang the uniform up to dry in the warmer indoor air to release the sweat from it.

The silver nanowires on the fabrics can bear repeated laundering, and the Scientists are presently working out on how best to apply the hydrogel so that it is equally durable. D'Angelo and her team will also explore the interaction between hydrogel and the silver mesh. The Researchers are also planning to use different power sources for the silver mesh, as batteries would add excess of weight to uniforms.

As soon as D'Angelo and her colleagues optimize the fabric for gloves, they might also apply the technology to clothing for the chest and legs. According to D'Angelo, this could ultimately find its way into consumer products.

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