Scientists have created a fabric that automatically adjusts heat to keep people warm or cool as the weather changes.
If the conditions are warm and moist, such as near the sweaty body, the fabric will pass heat. When the conditions become cooler and dry, the fabric reduces heat to escape.
Researchers at the University of Maryland have fabricated specially designed yarns coated with conductive metal.
This is the first fabric to control heat exchange with the environment, according to a study published in the journal Science.
In hot and humid conditions, the yarn is tapered and the coating is activated, changing the way the fabric interacts with the infrared radiation.
They are the "gating" of infrared radiation that acts as an adjustable blind that transmits or blocks heat.
Professor YuHuang Wang of the University of Maryland said: "This is the first technology we can use to dynamically pass infrared light.
The base yarn of this new fiber is made of fibers made of two different synthetic materials. One absorbs water and the other absorbs water.
Strands are coated with carbon nanotubes, and carbon nanotubes are made of carbon-based conductive metals. Since the material in the fibers resists and absorbs water, the fibers are bent when exposed to moisture, such as moisture surrounding the sweat body.
The distortion brings the strands of yarn closer together and opens the pores of the fabric. This is a small cooling effect because heat escapes.
The researchers say the coating changes the electromagnetic coupling between the carbon nanotubes, the researchers said.
"Considering this coupling effect, the curvature of the radio antenna is similar to changing the wavelength or frequency," Wang said.
"It's very simple to think, but imagine bringing two antennas close together and regulating the kind of electromagnetic waves they receive," he said.
"The closer the fibers are to each other, the more radiation they interact with, and in clothing it means the heat and textures emitted by the body interact."
Depending on the tuning, the fabric blocks or passes infrared radiation. The reaction is almost instantaneous, so people can already wear clothes and cool before they get hotter.
On the side of the flip, the body is cooling down and the dynamic gating mechanism works in reverse to trap heat.
"The body is a perfect radiator and it releases heat quickly," said Professor Min Ouyang of the University of Maryland.
"In all history, the only way to control the radiator was to take off the clothes and put on clothes, but this fabric is a true bi-directional device," Ouyang says.