Soldiering in arctic conditions is tough. Protective clothing can be heavy and can cause overheating and sweating upon exertion. And hands and feet can grow numb despite wearing such gear. To keep military personnel more comfortable and battle-ready in bitterly cold climes, scientists are now conducting research aimed at creating high-tech fabrics that heat up when powered and that capture sweat. These fabrics could also conceivably make their way to consumer clothing in the future.
Much of the Army’s cold-weather hand gear was designed more than 30 years ago, so soldiers often opt to buy winter gloves at retail stores, Paola D'Angelo, Ph.D., says. But even this modern gear isn’t enough to prevent paratroopers from losing feeling in their hands and feet when they parachute to earth in arctic conditions. “That’s problematic if soldiers have to operate weapons as soon as they land,” D’Angelo notes. “So we want to pursue this fundamental research to see if we can modify hand wear for that extreme cold weather.”
The work was inspired by research led by Yi Cui, Ph.D., at Stanford University. Cui’s team synthesized very fine silver nanowires, and then placed a network of the wires on cotton. By applying power to the silver nanowires, the researchers could heat the fabric.
D’Angelo, Elizabeth Hirst, Ph.D., and colleagues at the U.S. Army Natick Soldier Research, Development & Engineering Center, are working to extend this silver nanowire idea to fabrics suitable for military uniforms, such as polyester and a cotton/nylon blend. The Army team found that applying a mere 3 volts to 1-inch by 1-inch test swatches of these fabrics — the output of a typical watch battery — raises the temperature by 100 degrees Fahrenheit in just one minute. If these experimental fabrics can ultimately be used in uniforms, soldiers could dial up or down the voltage to vary the amount of heat their uniforms produce to match weather conditions. The added heating means uniforms could be thinner and lighter, an advantage for soldiers who must carry heavy loads and walk long distances.
The scientists are also incorporating a layer of sweat-absorbing hydrogel particles made of polyethylene glycol or poly(N-isopropylacrylamide). The researchers think these particles might stop other layers in the fabrics from getting wet, which would keep soldiers more comfortable during missions