Tex­tiles with a twist

Nano-yarns could soon rev­o­lu­tionise wear­able tech­nol­ogy.

Cosmos - - Digest -

It’s a rite of pas­sage in high-school physics to twist a length of string and then let it go to demon­strate how po­ten­tial energy con­verts to ki­netic energy.

Per­haps Carter Haines of the Univer­sity of Texas, Dal­las, was par­tic­u­larly im­pressed by this ev­er­green les­son. It would happily ex­plain the in­spi­ra­tion for an in­ven­tion he and col­leagues de­scribe in the jour­nal Sci­ence.

Haines’ team has cre­ated a new type of yarn from car­bon nan­otubes, which gen­er­ates elec­tric­ity when stretched or twisted. These “twistrons”, the sci­en­tists sug­gest, have a wide range of po­ten­tial uses, in­clud­ing har­vest­ing power from ocean waves, or func­tion­ing as a wear­able heart mon­i­tor.

To cre­ate the ba­sic struc­ture, Haines and col­leagues com­piled nan­otubes – tiny cylin­ders 10,000 times smaller than the width of a hu­man hair – and twisted them to­gether, like a strand of wool.

Be­fore that, how­ever, the yarns were coated with a con­duc­tive sub­stance – an elec­trolyte. High tech met low: salt wa­ter was all that was needed for proof of con­cept.

The tighter the yarns were twisted, the closer to­gether the elec­tric charges em­bed­ded in them be­came, in­creas­ing their energy out­put.

“Fun­da­men­tally, these yarns are su­per­ca­pac­i­tors,” says co-au­thor Na Li. “When you insert the car­bon nan­otube yarn into an elec­trolyte bath, the yarns are charged by the elec­trolyte it­self. No ex­ter­nal bat­tery, or volt­age, is needed.”

For such a sim­ple ma­chine, the elec­tri­cal out­put is im­pres­sive. The sci­en­tists cal­cu­lated that stretch­ing them 30 times a sec­ond pro­duced about 240 watts of power per kilo­gram of yarn.

Haines and his col­leagues have al­ready filed a patent on twistrons, and see them as a pos­si­ble so­lu­tion to one of the ma­jor hur­dles fac­ing man­u­fac­tur­ers of “smart” cloth­ing and other wear­ables. “Elec­tronic tex­tiles are of ma­jor com­mer­cial in­ter­est,” team mem­ber Ray Baugh­man notes, “but how are you go­ing to power them?”

CREDIT: UNIVER­SITY OF TEXAS AT DAL­LAS Smart-dressed: twisted car­bon nan­otubes might one day power your shirt.

SACHSEN-ANHALT, JURAJ LIPTÁK CREDIT: LANDESAMT FÜR DENKMALPFLEGE UND ARCHÄOLOGIE Tar pro­duced with­out ce­ram­ics, us­ing only Ne­an­derthal tech­nol­ogy.

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