High-tech fabrics with thermal properties that keep marathon runners cool or high-altitude hikers warm are nothing new, but until now there has never been a material that does both by changing its insulating properties in response to the environment.
Researchers at the University of Maryland have developed a “smart” fabric that automatically regulates the amount of heat that passes through it depending on conditions. For example, when conditions are wet and warm, such as on a hot summer day, the fabric allows heat from the body to e
A paper on their work was just published in the journal Science.
Infrared radiation is the primary way the body releases heat and is the focus of this new technology. “This is the first technology that allows us to dynamically gate [regulate] infrared radiation,” said YuHuang Wang, a UMD professor of chemistry and biochemistry and one of the authors of the paper.
The researchers created the fabric from specially engineered yarn coated with a conductive metal. Under hot, humid conditions, the strands of yarn contract and activate the coating, which changes the way the fabric interacts with infrared radiation to allow more heat to pass through.
The base yarn for this fabric is made from two different synthetic materials—one absorbs water and the other repels it. The strands are then coated with carbon nanotubes, a special class of lightweight, carbon-based metal. Because the materials of the fabric both repel and absorb water, they warp when exposed to humidity from a sweating body. The contracting and warping brings the strands of yarn closer together which opens the pores in the fabric and most importantly, modifies the electromagnetic coupling between the carbon nanotubes in the coating.
“You can think of this coupling effect like the bending of a radio antenna to change the wavelength or frequency it resonates with,” Wang said. “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.”
Depending on the tuning, the fabric either blocks infrared radiation or allows it to pass through. The reaction is almost instant, so before people realize they’re getting hot, the fabric could already be cooling them down. Reversely, as a body cools down, the gating mechanism works in reverse to trap heat.
“The human body is a perfect radiator. It gives off heat quickly,” said Min Ouyang, a professor of physics at UMD and the paper’s other corresponding author. “For all of history, the only way to regulate the radiator has been to take clothes off or put clothes on. But this fabric is a true bidirectional regulator.”
More work is needed before it can be commercialized, but according to the researchers, materials used for the base fiber are readily available and the carbon coating can be easily added during