The DQWeek (Kolkata) - - CHANNEL BONANZA -

Sci­en­tists have de­vel­oped a new self-heal­ing ma­te­rial that con­ducts ions to gen­er­ate cur­rent, and could one day help your bro­ken smart­phone to re­pair it­self. Re­searchers cre­ated the stretch­able and trans­par­ent poly­meric ma­te­rial with an eye on elec­tron­ics and soft robotics that can re­pair them­selves.

“A self-heal­ing ma­te­rial, when carved into two parts, can go back to­gether like noth­ing has hap­pened, just like our hu­man skin,” said Chao Wang from Univer­sity of Cal­i­for­nia, River­side in the US. “I have been re­search­ing mak­ing a self­heal­ing lithium ion bat­tery, so when you drop your cell phone, it could fix it­self and last much longer,” said Wang.

The key to self-re­pair is in the chem­i­cal bond­ing. Two types of bonds ex­ist in ma­te­ri­als, Wang said. There are co­va­lent bonds, which are strong and do not read­ily re­form once bro­ken; and non­co­va­lent bonds, which are weaker and more dy­namic. The hy­dro­gen bonds that con­nect wa­ter mol­e­cules to one an­other are non-co­va­lent, break­ing and re­form­ing con­stantly to give rise to the fluid prop­er­ties of wa­ter.

“Most self-heal­ing poly­mers form hy­dro­gen bonds or metal-lig­and co­or­di­na­tion, but these are not suit­able for ionic con­duc­tors,” Wang said. Wang’s team turned in­stead to a dif­fer­ent type of non-co­va­lent bond called an iondipole in­ter­ac­tion, a force be­tween charged ions and po­lar mol­e­cules.

“Ion-dipole in­ter­ac­tions have never been used for de­sign­ing a self-heal­ing poly­mer, but it turns out that they are par­tic­u­larly suit­able for ionic con­duc­tors,” Wang said. The key de­sign idea in the de­vel­op­ment of the ma­te­rial was to use a po­lar, stretch­able poly­mer, poly(vinyli­dene flu­o­ride-co­hex­aflu­o­ro­propy­lene), plus a mo­bile, ionic salt.

The poly­mer chains are linked to each other by ion-dipole in­ter­ac­tions be­tween the po­lar groups in the poly­mer and the ionic salt.

The re­sult­ing ma­te­rial could stretch up to 50 times its usual size. Af­ter be­ing torn in two, the ma­te­rial au­to­mat­i­cally stitched it­self back to­gether com­pletely within one day. As a test, the re­searchers gen­er­ated an “ar­ti­fi­cial mus­cle” by plac­ing a non-con­duc­tive mem­brane be­tween two lay­ers of the ionic con­duc­tor.

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