Ex­perts make heat reg­u­lat­ing fab­ric

‘ Gat­ing’ of ra­di­a­tion acts as a blind to trans­mit or block heat

The Asian Age - - World -

Washington, Feb. 10: Sci­en­tists cre­ated a fab­ric that can au­to­mat­i­cally reg­u­late the amount of heat that passes through it, help­ing a per­son stay cool or warm de­pend­ing on the weather con­di­tions.

When con­di­tions are warm and moist, such as those near a sweat­ing body, the fab­ric al­lows heat to pass through. When con­di­tions be­come cooler and drier, the fab­ric re­duces the heat that es­capes, re­searchers said.

The re­searchers from Uni­ver­sity of Mary­land in the US cre­ated the fab­ric from spe­cially en­gi­neered yarn coated with a con­duc­tive metal.

This is first tex­tile shown to be able to reg­u­late heat ex­change with the en­vi­ron­ment, ac­cord­ing to the study pub­lished in the jour­nal Sci­ence.

Un­der hot, hu­mid con­di­tions, the strands of yarn

■ The fab­ric cre­ated from spe­cially en­gi­neered yarn coated with a con­duc­tive metal.

■ This is first tex­tile shown to be able to reg­u­late heat ex­change with the en­vi­ron­ment

com­pact and ac­ti­vate the coat­ing, which changes the way the fab­ric in­ter­acts with in­frared ra­di­a­tion.

They re­fer to the ac­tion as “gat­ing” of in­frared ra­di­a­tion, which acts as a tun­able blind to trans­mit or block heat.

“This is the first tech­nol­ogy that al­lows us to dy­nam­i­cally gate in­frared ra­di­a­tion,” said YuHuang Wang, a pro­fes­sor at

■ Un­der hot, hu­mid con­di­tions, the strands of yarn com­pact and ac­ti­vate the coat­ing

■ De­pend­ing on the tun­ing, the fab­ric ei­ther blocks in­frared ra­di­a­tion or al­lows it to pass through

Uni­ver­sity of Mary­land.

The base yarn for this new tex­tile is cre­ated with fi­bres made of two dif­fer­ent syn­thetic ma­te­ri­als -one ab­sorbs wa­ter and the other re­pels it.

The strands are coated with car­bon nan­otubes, a spe­cial class of light­weight, car­bon- based, con­duc­tive metal. Since 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 opens the pores in the fab­ric. This has a small cool­ing ef­fect be­cause it al­lows heat to es­cape.

It also mod­i­fies the elec­tro­mag­netic cou­pling be­tween the car­bon nan­otubes in the coat­ing, re­searchers said.

“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,” he said.

“When the fi­bres 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,” he added.

De­pend­ing on the tun­ing, the fab­ric ei­ther blocks in­frared ra­di­a­tion or al­lows it to pass through. The re­ac­tion is al­most in­stant, so be­fore people re­alise they're get­ting hot, the gar­ment could al­ready be cool­ing them down.

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