Duke University : Textile vents release heat ...
Duke University

Textile vents release heat during sweating

(Source: Duke University)
(Source: Duke University)

A prototype patch made of hybrid PA/silver vents opens in response to a person’s sweat and closes again once dry. Requiring no energy, the vents open because the moist polyamide (PA) must expand but the silver can only curl in on itself.  
Materials scientists at Duke University, Durham, NC/USA, have developed the lightweight material that traps thermal energy. Using physics rather than electronics to open the vents, the material has potential as a patch on various types of clothing to help keep the wearer comfortable in a wide range of situations.
When the bottom layer of PA gets wet, it wants to expand like a sheet being pulled from its sides. But because it is attached to the silver on top, it cannot stretch in those directions. The easiest option remaining is for the 2-layer material to curl up, allowing the PA to expand while forcing the silver to shrink.
In the experiments, the researchers created a patch about the size of a human hand with flaps a few millimeters long. Compared with an average traditional textile represented by a blend of polyester (PET) and elastane (spandex), the material is about 16% warmer when dry with the flaps closed and 14% cooler when humid with the flaps open. Put together, the PA-silver hybrid can expand the thermal comfort zone by 30%. According to researchers, this approach has advantages to existing methods of venting heat through warm clothing, such as placing zippers beneath the armpits.

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