Fabrics embedded with nanowires and hydrogels could help soldiers to keep warm and comfortable in colder climates.
Some of the winter weather gear worn by the US Army was designed 30 years ago. It’s heavy and can cause overheating during exertion, while also not doing a very good job of keeping the extremities from going numb.
“That's problematic if soldiers have to operate weapons as soon as they land,” said Paola D'Angelo, a research bioengineer at the US Army’s Natick Soldier Research, Development and Engineering Center in Massachusetts. “So we want to pursue this fundamental research to see if we can modify hand wear for that extreme cold weather.”
So scientists are developing smart fabrics that heat up when powered, and can capture sweat. The work, which was presented at the 254th National Meeting and Exposition of the American Chemical Society, is based on research from Stanford University in California. A team there embedded a network of very fine silver nanowires in cotton, and was able to heat the fabric by applying power to the wires.
D’Angelo and her colleagues are working to extend the approach to other fabrics more suitable for military uniforms, including polyester and a cotton/nylon blend. By applying three volts – the output of a typical watch battery – to a one-inch square of fabric, they were able to raise its temperature by almost 40 degrees C.
The idea is that soldiers would be able to dial the voltage up or down to vary the amount of heat. The system would mean that uniforms could be lighter and thinner.
The researchers are also incorporating a layer of hydrogel particles made of polyethylene glycol that will absorb sweat and stop the other layers of the fabric from getting wet.
“Once we have optimised the coating, we can start looking at scaling up,” D’Angelo told Professional Engineering. She said the fabric has been tested with up to three washes, and still works the same as unwashed fabric for most of the textiles being tested.
The process for integrating the nanowires varies depending on the type of fabric being used. “Some can simply be immersed in nanowire ink for some time and let dry,” she explained. “Others may need a chemical process to get the fabric ready before coating the nanowires. Production of the nanowires is very simple and not as expensive as you may think, so it may be possible to mass-produce relatively easy. However, since this research is in the early stages we have not started looking into mass-production.”
She is confident that the technology could have non-military uses too. “I think this could ultimately be beneficial to anyone that is exposed to extreme cold weather, from researchers that work in Arctic climates to people that like to go skiing,” she said.