Sci­en­tists cre­ate unique fab­ric for cool clothes

China Daily (USA) - - TOP NEWS - By LIA ZHU in San Fran­cisco li­azhu@chi­nadai­

Chi­nese re­searchers at Stan­ford Uni­ver­sity have de­vel­oped a plas­tic-based tex­tile that can cool the hu­man body and may some­day re­duce de­mand for air con­di­tion­ing.

The ma­te­rial cools by not only tak­ing away sweat like or­di­nary fab­rics do but also by al­low­ing the heat that the body emits as in­frared ra­di­a­tion to pass through, which makes the wear­ers feel cooler than they would when wear­ing cot­ton clothes, ac­cord­ing to the re­searchers’ study, re­cently pub­lished in the jour­nal Science.

By­cool­ing thep­er­son­rather than an en­tire build­ing, a sub­stan­tial im­pact could be made on global en­ergy use, ac­cord­ing to Yi Cui, an as­so­ci­ate pro­fes­sor of ma­te­ri­als science and engi­neer­ing at Stan­ford and the lead au­thor of the study.

The­hu­man­bodyemitsmid­in­frared ra­di­a­tion, an in­vis­i­ble and be­nign wave­length of light. That con­trib­utes to­more than 50 per­cent of the to­tal body-heat loss in a typ­i­cal in­door set­ting like an of­fice.

How­ever, tra­di­tional tex­tiles are not de­signed for in­frared ra­di­a­tion con­trol.

To en­hance ra­dia­tive dis­si­pa­tion in hot weather, the re­searchers used nanoporous poly­eth­yl­ene, or nanoPE, a vari­ant of poly­eth­yl­ene widely used in bat­tery­mak­ing, which al­lows in­frared ra­di­a­tion to pass through it while opaque to vis­i­ble light.

There are also other chal­lenges that the re­searchers need to ad­dress be­yond en­sur­ing the cool­ing ef­fect, such as wick­ing, me­chan­i­cal strength and air per­me­abil­ity, which are im­por­tant for a tex­tile to be wear­able.

The re­searchers al­tered nanoPE through a num­ber of pro­cesses in or­der to make it into a suit­able hu­man cloth.

They first cre­ated mi­cro­holes as thin as hu­man hairs with com­monly used mi­cronee­dle punch­ing, re­sem­bling the spac­ing be­tween­the yarns in wo­ven cot­ton tex­tiles.

Be­cause the hole is so small, the vis­ual opac­ity is not af­fected. The wick­ing rate and the me­chan­i­cal strength of the new ma­te­rial also are com­pa­ra­ble to cot­ton, ac­cord­ing to the study.

To make the thin ma­te­rial more fab­ric-like, the re­searchers cre­ated a three­layer ma­te­rial with two sheets of treated poly­eth­yl­ene sand­wich­ing a cot­ton mesh for strength and thick­ness.

They then tested the cool­ing ef­fect of nanoPE with a de­vice that sim­u­lated the heat out­put of skin. The ma­te­rial in­creases the sim­u­lated skin tem­per­a­ture lessthancot­ton, they­said.

Though the tem­per­a­ture dif­fer­ence is small, it­can­make a dif­fer­ence for air con­di­tion­ing set­points, the re­searchers said, which means some­one dressed in the new ma­te­rial may not feel the need to turn on the air con­di­tioner. be­ing

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