A prototype patch made of hybrid nylon/silver vents that open in response to a person's sweat and close again once dry. Requiring no energy, the vents open because the nylon must expand. Credit: Po-Chun Hsu, Duke University.
The scientists at Duke University have developed a lightweight material that traps thermal energy when dry, but opens a series of tiny vents to let heat escape when a person starts sweating. Once they are dry, the vents close again.
The material can be used as a patch on clothing to help keep the wearer comfortable in a wide range of situations.
The approach is described in a journal.
Po-Chun Hsu, assistant professor of mechanical engineering and materials science at Duke, said that people who are skiing or hiking in cold weather usually wear layers so they can adjust how much heat their clothing is trapping. One could make a one-piece-fits-all textile by strategically placing patches of a material that can let out heat when a person is sweating.
When he tried to make a dual-purpose material, he turned to nylon. It's inexpensive, lightweight and soft, and Hsu knew that if cut into flaps, nylon would get a little wet.
The silver on top of the nylon was heat-trapping and not known for making warm clothing. He tried to make the layer as thin as possible, expecting the weight of silver to cause problems. The silver addition made the flaps curl back even more.
The Goldilocks spot is around 50 nanometers and is2,000 times thinner than a sheet of paper. The phenomena wouldn't be as strong if it were thinner. The weight of silver interfered with the opening of the vent.
He turned to a Duke professor who was also a mechanical engineering and materials science chair to find out what was going on. Brinson was able to give an explanation while working with her graduate student.
A single strip of nylon/silver material is affected by the humidity. If placed over a large area, researchers hope to make a patch that keeps people warm when the vents are closed. Credit: Po-Chun Hsu, Duke University.
Brinson said that adding something heavy on top of a polymer can make it bend and open more. The silver is Shrinking and the nylon is Expanding.
Brinson and Ma explained that when the nylon is wet, it wants to expand like a sheet being pulled from its sides. It can't stretch in those directions because it's attached to silver. The easiest option is for the nylon to expand and the silver to shrink.
The researchers created a patch about the size of a human hand with flaps that were about the size of a fingernail. When dry, the material is about 16% warmer than an average traditional textile, and when humid, it is about 14% cooler. The nylon-silver hybrid can expand the thermal comfort zone by 30%. This approach has advantages to the existing methods of cooling heat through warm clothing, such as putting a zip up under the armpits.
"We want the sweating parts of the body to be open, which is not necessarily the underarms," he said. The effort to open our chest and back is almost the same as taking off our clothing.
The vents are being made as small as possible while retaining their effectiveness. He's looking at using a top layer of a material that could make it any color without changing its thermal attributes.
If we can find a way to create small flaps and attach a patch to clothing, we can create this effect without looking like we're wearing a costume," said Hsu. This kind of material could look very similar to what we're wearing.
The Metalized polyamide Heterostructure is a moisture-responsive actuator for multimodal adaptive personal heat management. Science.org has an article titled "Sci Adv. abj7906."
Science Advances has journal information.
The news about innovative textile vents to release heat when you sweat was retrieved from thephys.org.
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