Sci­en­tists cre­ate pat­terned graphene onto food, pa­per, cloth, card­board

Iran Daily - - Science & Technology -

Sci­en­tists from Rice Uni­ver­sity who in­tro­duced laserin­duced graphene (LIG) have en­hanced their tech­nique to pro­duce what may be­come a new class of ed­i­ble elec­tron­ics.

The Rice lab of chemist James Tour, which once turned Girl Scout cook­ies into graphene, is in­ves­ti­gat­ing ways to write graphene pat­terns onto food and other ma­te­ri­als to quickly embed con­duc­tive iden­ti­fi­ca­tion tags and sen­sors into the prod­ucts them­selves, ac­cord­ing to

Tour said, “This is not ink. This is tak­ing the ma­te­rial it­self and con­vert­ing it into graphene.”

The process is an ex­ten­sion of the Tour lab’s con­tention that any­thing with the proper car­bon con­tent can be turned into graphene.

In re­cent years, the lab has de­vel­oped and ex­panded upon its method to make graphene foam by us­ing a com­mer­cial laser to trans­form the top layer of an in­ex­pen­sive poly­mer film.

The foam con­sists of mi­cro­scopic, cross-linked flakes of graphene, the twodi­men­sional form of car­bon.

LIG can be writ­ten into tar­get ma­te­ri­als in pat­terns and used as a su­per­ca­pac­i­tor, an elec­tro­cat­a­lyst for fuel cells, ra­dio-fre­quency iden­ti­fi­ca­tion (RFID) an­ten­nas and bi­o­log­i­cal sen­sors, among other po­ten­tial ap­pli­ca­tions.

The new work re­ported in the Amer­i­can Chem­i­cal So­ci­ety jour­nal ACS Nano demon­strated that laserin­duced graphene can be burned into pa­per, card­board, cloth, coal and cer­tain foods, even toast.

Tour said, “Very of­ten, we don’t see the ad­van­tage of some­thing un­til we make it avail­able.

“Per­haps all food will have a tiny RFID tag that gives you in­for­ma­tion about where it’s been, how long it’s been stored, its coun­try and city of ori­gin and the path it took to get to your table.”

He added LIG tags could also be sen­sors that de­tect E. coli or other micro­organ­isms on food.

“They could light up and give you a sig­nal that you don’t want to eat this. All that could be placed not on a sep­a­rate tag on the food, but on the food it­self.”

Mul­ti­ple laser passes with a de­fo­cused beam al­lowed the re­searchers to write LIG pat­terns into cloth, pa­per, pota­toes, co­conut shells and cork, as well as toast. (The bread is toasted first to ‘car­bonize’ the sur­face). The process hap­pens in air at am­bi­ent tem­per­a­tures. Tour said, “In some cases, mul­ti­ple las­ing cre­ates a two-step re­ac­tion.

“First, the laser pho­tother­mally con­verts the tar­get sur­face into amor­phous car­bon.

“Then on sub­se­quent passes of the laser, the se­lec­tive ab­sorp­tion of in­frared light turns the amor­phous car­bon into LIG. We dis­cov­ered that the wave­length clearly mat­ters.”

The re­searchers turned to mul­ti­ple las­ing and de­fo­cus­ing when they dis­cov­ered that sim­ply turn­ing up the laser’s power didn’t make bet­ter graphene on a co­conut or other or­ganic ma­te­ri­als.

But ad­just­ing the process al­lowed them to make a mi­cro su­per­ca­pac­i­tor in the shape of a Rice ‘R’ on their twice-lased co­conut skin.

De­fo­cus­ing the laser sped the process for many ma­te­ri­als as the wider beam al­lowed each spot on a tar­get to be lased many times in a sin­gle raster scan.

Tour said, “That also al­lowed for fine con­trol over the prod­uct. De­fo­cus­ing al­lowed them to turn pre­vi­ously un­suit­able polyether­im­ide into LIG.”

Rice grad­u­ate stu­dent Yieu Chyan, co-lead au­thor of the pa­per, said, “We also found we could take bread or pa­per or cloth and add fire re­tar­dant to them to pro­mote the for­ma­tion of amor­phous car­bon.

“Now we’re able to take all these ma­te­ri­als and con­vert them di­rectly in air with­out re­quir­ing a con­trolled at­mos­phere box or more com­pli­cated meth­ods.”

Tour added, “The com­mon ele­ment of all the tar­geted ma­te­ri­als ap­pears to be lignin.”

An ear­lier study re­lied on lignin, a com­plex or­ganic poly­mer that forms rigid cell walls, as a car­bon pre­cur­sor to burn LIG in oven-dried wood.

Cork, co­conut shells and potato skins have even higher lignin con­tent, which made it eas­ier to con­vert them to graphene.

Tour said that flex­i­ble, wear­able elec­tron­ics may be an early mar­ket for the tech­nique.

“This has ap­pli­ca­tions to put con­duc­tive traces on cloth­ing, whether you want to heat the cloth­ing or add a sen­sor or con­duc­tive pat­tern.” Laser-in­duced graphene is a highly con­duc­tive ad­di­tion to a piece of bread. A Rice Uni­ver­sity lab is us­ing an in­dus­trial laser to write graphene pat­terns on ev­ery­day ob­jects, in­clud­ing food, cloth, card­board and wood.

Newspapers in English

Newspapers from Iran

© PressReader. All rights reserved.