Graphene origami produced by world’s thinnest folds
An ancient art just got an extremely modern update. Researchers can now fold origami shapes from graphene, the 1-atom-thick sheets of carbon. The technique could be used to build tiny three-dimensional structures like nano-robots and flexible circuits.
Graphene is a sheet of carbon atoms linked together in one layer and is prized for its variety of “wonder properties” – it’s the strongest material ever studied and is a powerful electrical conductor. Researchers are using origami, the Japanese art of paper-folding, to bend graphene into different shapes. Last year, a team in China built a self-folding origami robot from multiple layers of graphene oxide sheets, and the bot could walk and turn a corner.
But until now, no one has been able to make an origami crease in just a single sheet, says Itai Cohen of Cornell University in Ithaca, New York. “Folding rules are the same at the macro scale or the micro scale,” he says it’s just much more difficult to fold a few atoms at a time, because of their size and fragility.
Researchers on Cohen’s team coated a single layer of graphene with a single layer of silicon dioxide glass, which was half a nanometre thick. The team found that the glass molecules respond differently to the linked carbon atoms when heated, exposed to an electric charge, or soaked in a liquid with a different pH level. These three responses let the team predict how the graphene sheet would expand and contract to produce an instant fold. “This really represents the limit,” says Cohen. “There’s not going to be any way to make the sheet any thinner.”
In future, the team hopes that adding other compounds like gold, semiconductors and insulators, will let them create two-dimensional circuits that can be folded into any desirable shape using origami techniques.
“You can imagine printing your entire circuit on one of these sheets, then folding it up into a three-dimensional structure that can absorb light, do some kind of calculation, and report back by emitting light at a different frequency,” Cohen says. “This work is about being able to build the folding technology, but we’re starting to work with origami artists to fold cool things.”
The team is presenting its work this week at the American Physical Society annual meeting in Baltimore, Maryland.
Image: Itai Cohen Group/Mark Miskin/Cornell University