Wearable gadgets are making clothes smarter all the time, but one of the most basic functions you'd want in a garment – the ability to warm you up or cool you down as needed – is still frustratingly elusive. Now, researchers at the University of Maryland (UMD) have developed a new material that senses how warm a person's body is and automatically adjusts how much heat it traps or releases.

One of the easiest ways to regulate your body temperature is just to put on or take off layers. But previous work in smarter clothing has led to different solutions, such as a reversible jacket that was cooling on one side and warming on the other, so you could turn it inside out as needed. A higher-tech attempt to fix the problem was a "robotic" jacket that used machine learning algorithms to judge how hot or cold a person was and open or close vents accordingly.

The UMD fabric seems like a much more elegant solution. Its creators say clothes made of the stuff would be able to automatically react to infrared radiation, which is the human body's main way of releasing heat, and let it pass through to the outside air.

To do this, the fibers are made of two different synthetic materials, one that absorbs water and one that repels it, both of which are then coated in carbon nanotubes. The idea is, when water (i.e. sweat) gets absorbed by half of each fiber, it distorts the fibers so they come closer together. That allows the fabric to cool the wearer in two ways at once.

First, it opens up the pores of the material, allowing more heat to escape. Secondly, the more active cooling comes from bringing the carbon nanotubes closer together. That changes the electromagnetic coupling, "tuning" the nanotubes to absorb over 35 percent more infrared radiation and draw away more heat from the wearer.

"You can think of this coupling effect like the bending of a radio antenna to change the wavelength or frequency it resonates with," says YuHuang Wang, corresponding author of the study. "It's a very simplified way to think of it, but imagine bringing two antennae close together to regulate the kind of electromagnetic wave they pick up. When the fibers are brought closer together, the radiation they interact with changes. In clothing, that means the fabric interacts with the heat radiating from the human body."

The team says this dynamic infrared gating makes the fabric the first "true bidirectional regulator" of body heat, and it apparently kicks in before the wearer even realizes they're getting too hot.

It definitely does sound less cumbersome than an AI-enabled jacket, and according to the creators all the materials are already easily available on the market, while the carbon nanotube coating can be applied during the regular dying process.

The research was published in the journal Science.

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