Keeping safe and comfortable in arctic conditions is a precarious balancing act between protecting one's self against the cold without overheating. This is particularly true of a soldier's hands and feet while working in the cold, so scientists from Stanford University and the US Army Natick Soldier Research, Development & Engineering Center are working on energized fabrics that heat up when powered, yet wick away sweat and dry easily.
If there's one constant in military life, it's that the issued kit isn't all that should be – especially when it comes to gloves and boots. It's for this reason that many armed services allow their members to buy items of kit commercially that are better suited, yet still meet military specifications.
According to Paola D'Angelo at Natick, the US Army has a particular problem because the cold weather gloves used by its soldiers were designed 30 years ago and often leave personnel with cold, numbed hands. The same is true of the footwear, and the cold-weather gear in general suffers from the problem of how to keep soldiers warm in bitterly cold conditions, yet not overheat and cause them to sweat while exerting themselves. The latter is of particular importance because damp, sweaty arctic gear can be fatal in subzero temperatures.
To help alleviate this, the US Army-funded basic research project is looking into developing new fabric with a focus on cold-weather gloves. The idea is to incorporate very fine silver nanowires set in military-grade fabrics, like polyester and a cotton/nylon blend. By applying three volts to a 1 x 1 in (2.5 x 2.5 cm) test swatch, the temperature of the swatch can be raised by 100° F (56° C) in one minute.
The ultimate goal is to produce uniforms that can withstand repeated washings and that soldiers could adjust the temperature of by simply dialing up and down the voltage. This would not only provide better warmth with less sweating, but would also make the garments lighter. To further lighten the load, the researchers are looking at alternative power sources to reduce the need for batteries.
As another refinement, the team is also including a layer of hydrogel particles consisting of polyethylene glycol or poly(N-isopropylacrylamide). This hydrogel might be able to absorb sweat and keep moisture from migrating from one layer of fabric to another, keeping soldiers drier and more comfortable. On return to base, the sweat could be allowed to evaporate by simply hanging the uniforms up to dry.
Though the silver nanowires are able to handle repeat laundering, the team still needs to determine the durability of the hydrogel layer and its compatibility with the nanowires. After completing work on energized gloves, the next step will be to apply the fabric to other articles of clothing for the torso and legs. Eventually, the technology may even end up in consumer goods.
The research was presented at the 254th National Meeting & Exposition of the American Chemical Society (ACS).
Source: American Chemical Society
