University of Maryland (UMD) researchers have created a fabric that can automatically regulate the amount of heat that passes through it•△☆…◇. When conditions are warm and moist▷▽▼□●, such as those near a sweating body■▷▲□▼, the fabric allows infrared radiation▲●…, i▷▽○.e•■▷◆○.△…◇◇, heat▽☆●…, to pass through-△-•. When conditions turn cooler and drier◁○, the fabric reduces the heat that escapes=★◆-.
The development was reported in the February 8 issue of the journal &lsquo•-□▪▼;Science&rsquo★▲-;=●.
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□▼-. They refer to the action as &lsquo-○◇●△;gating&rsquo•▽□; of infrared radiation▪●, which acts as a tunable blind to transmit or block heat☆○.
&quot•▼●○;This is the first technology that allows us to dynamically gate infrared radiation☆-,&quot▷•; said YuHuang Wang■■▷, a professor of chemistry and biochemistry at UMD and one of the paper&rsquo▪=•••;s corresponding authors▷□.
The base yarn for this new textile is created with fibres made of two different synthetic materials&mdash-●■◇○;one absorbs water and the other repels it△▪◁. The strands are coated with carbon nanotubes★□, a special class of lightweight☆□, carbon-based▽◆★◆▲, conductive metal◇○▷◇★.
Because materials in the fibres both resist and absorb water▷■, the fibres 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▲▪☆.
&quot★■•○;You can think of this coupling effect like the bending of a radio antenna to change the wavelength or frequency it resonates with……•,&quot▲•; a press release from the university quoted Wang as saying•●▽-.
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&rsquo…□◇;re getting hot•☆●☆, the garment could already be cooling them down☆•▲□★. On the flip side■☆◇★, as a body cools down▷□=□•, the dynamic gating mechanism works in reverse to trap in heat■▷△-★.
According to the Science paper•…•▲●, this is first textile shown to be able to regulate heat exchange with the environment▷☆.
More work is needed before the fabric can be commercialized▲•…☆▪, but according to the researchers□▷=, materials used for the base fibre are readily available and the carbon coating can be easily added during standard dying process•▽◁. (DS)