Fabric Regulates Heat Exchange With the Environment

For the first time, scientists have developed a fabric that automatically regulates the amount of heat that passes through it. When conditions are warm and moist, such as those near a perspiring body, the material allows infrared radiation (heat) to pass through. When conditions become cooler and drier, the fabric reduces the heat that escapes.

A team from the University of Maryland created the fabric from specially engineered yarn coated with a conductive metal. Under hot, humid conditions, the strands of yarn compact and activate the coating, which changes the way the fabric interacts with infrared radiation. The scientists refer to the action as “gating” of infrared radiation, which acts as a tunable blind to transmit or block heat.

“This is the first technology that allows us to dynamically gate infrared radiation,” said YuHuang Wang, a professor of chemistry and biochemistry.

The base yarn for the textile is created with fibers made of two different synthetic materials—one absorbs water and the other repels it. The strands are coated with carbon nanotubes, a special class of lightweight, carbon-based, conductive metal. Because materials in the fibers both resist and absorb water, the fibers warp when exposed to humidity such as that surrounding a sweating body. That distortion brings the strands of yarn closer together, which does two things: first, it opens the pores in the fabric; this has a small cooling effect because it allows heat to escape, and second, it modifies the electromagnetic coupling between the carbon nanotubes in the coating.

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