New fabric opens air vents when you sweat

Thanks to the tiny flaps and the silver coating on the outside, the new fabric is both warm and cool at the same time.

When it's hot and sweaty, people often prefer breathable clothing like mesh. However, the net is not enough to keep the body warm at normal times. To solve this problem, Associate Professor Po-Chun Hsu and colleagues at Duke University, North Carolina, developed a new fabric with breathable vents that automatically open when absorbing sweat. The new study was published in the journal Science Advances on December 15.

Cloth with vents open for perspiration (left) and closed when dry (right).

Basically, the new material is nylon with a thin silver coating on one side and many tiny flips cut. When the inner side, in contact with the skin and not coated with silver, absorbs water or perspiration, it swells. This phenomenon causes the flips to curve outward. Then, as the material dries, the nylon shrinks back to its original size and the flaps close.

The team added a 50-nanometer thick layer of silver to reflect heat radiating from the body inward, helping to keep the wearer warm when the flaps are closed. At first, Hsu wondered if the weight of the metal would interfere with the flexing effect of the flip sheet. But in fact, the silver layer also increases efficiency. This is because the silver layer on the top of each flip plate doesn't swell, forcing the nylon underneath to expand at the bottom more than the top, causing it to curve further.

To test the cooling effect, the team of scientists fabricated a cloth measuring 6 cm x 6 cm with flaps several millimeters long. As a result, compared with a closed panel made of a traditional polyester-spandex blend, the breathable fabric stays 16 percent warmer when the flaps are closed and 14 percent cooler when they're open.

Instead of making whole clothes from the new fabric, the team thinks it's possible to attach pieces of fabric in certain locations where people sweat a lot. They are working on ways to shrink the flips without losing their effectiveness, and hope to replace silver with a nanocomposite material that can be made in any color.