By Josh Perry, Editor
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Researchers at the University of Maryland (College Park, Md.) developed the first fabric that will automatically control the amount of heat that passes through it depending on environmental conditions, according to a report from the university.

This new fabric is the first textile to automatically change properties to trap or release heat depending on conditions. (Faye Levine/University of Maryland)

If conditions are hot and moist, such as when a person is sweating, the fabric allows infrared radiation to pass through, but when conditions are colder and drier the fabric blocks infrared radiation from escaping.

A specially-designed yarn coated with carbon nanotubes. When faced with heat and humidity, the yarn strands compact to allow more heat to pass through.

“The base yarn for this new textile is created with fibers made of two different synthetic materials—one absorbs water and the other repels it,” the article explained. “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. Second, and most importantly, it modifies the electromagnetic coupling between the carbon nanotubes in the coating.”

Researchers demonstrated that the coupling can be tuned to allow heat to pass through or to block it and that the reaction of the yarn strands is automatic, so the wearer wouldn’t notice the change but would instead stay comfortable.

While the process is not ready for commercialization, researchers insist the fabrics for the yarn and the carbon nanotubes can be added in a standard dying process.

The research was recently published in Science. The abstract stated:

“The human body absorbs and loses heat largely through infrared radiation centering around a wavelength of 10 micrometers. However, neither our skin nor the textiles that make up clothing are capable of dynamically controlling this optical channel for thermal management.

“By coating triacetate-cellulose bimorph fibers with a thin layer of carbon nanotubes, we effectively modulated the infrared radiation by more than 35% as the relative humidity of the underlying skin changed. Both experiments and modeling suggest that this dynamic infrared gating effect mainly arises from distance-dependent electromagnetic coupling between neighboring coated fibers in the textile yarns.

“This effect opens a pathway for developing wearable localized thermal management systems that are autonomous and self-powered, as well as expanding our ability to adapt to demanding environments.”