University of Maryland (UMD) researchers have created a new fabric that cools or insulates its wearer depending on the weather.
Fabrics that possess high-tech thermal properties and keep marathon runners cool or alpine hikers warm have already been on the market for some time now.
However, there has never been a material that changes its insulating properties in response to the environment.
UMD’s fabric can automatically regulate the amount of heat that passes through it depending on conditions.
For example, when conditions are warm and moist, such as those of a sweating body on a summer day, the fabric allows infrared radiation to pass through.
When conditions become cooler and drier, the fabric reduces the heat that escapes.
The new technology is based on infrared radiation which is a primary way the body releases heat.
The researchers 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 to allows more heat.
The researchers call this action as ‘gating’ of infrared radiation, which acts as a tunable blind to transmit or block heat.
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 strands are coated with carbon nanotubes.
Because materials in the fibers both resist and absorb water, the fibers warp when exposed to humidity such as that surrounding a sweating body.
This distortion between the strands 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.
Depending on the tuning, the fabric either blocks infrared radiation or allows it to pass through.
According to the researchers, the reaction is almost instant, so before people realize they’re getting hot, the garment could already be cooling them down.
Moreover, as a body cools down, the dynamic gating mechanism works in reverse to trap in heat.
Image and content: University of Maryland