Graphene manufacturing techniques have come a long way from the early 2000s, when scientists would use tape to laboriously scrape it away from a hunk of pencil lead. A new method published Wednesday in Nature (subscription required) takes inspiration from beetles and tree frogs, whose feet informed researchers how they can more effectively integrate graphene into electronics and other devices.
Graphene, an atom-thick layer of carbon atoms, is renowned for its unmatched strength and conductivity. It is theoretically a great fit for use in electronic chips and solar cells, but researchers need to figure out how to manufacture it reliably in large batches before it is commercially viable.
In this case, the researchers added it to a silicon wafer, which can be used to make a circuit, among other things. They were able to grow and attach graphene to the wafer in a single step.
The process begins with a layer of copper-based catalyst coating the silicon disc. The catalyst enables graphene to grow, but you don’t want it to stick around after the graphene has formed. So the researchers grew graphene on the catalyst and then used bubbles to adhere it to the disc. Even as the catalyst was removed, the graphene stayed in place, finally adhering to the silicon. Gases injected into the wafer further helped prevent the graphene from splitting from the silicon.
These bubbles were inspired by beetles and tree frogs, whose feet use similar bubbles to stick to submerged leaves. The bubbles form capillary bridges: stretched structures that exert an inward force on both ends, holding them together. It is the same effect that holds a sand castle together.
The current best way to manufacture graphene happens in an oven, where at high temperatures carbon is pulled from the air and deposited on copper in layers of graphene. The technique can yield nice, big sheets of graphene that could soon be manufactured into electronics in large quantities via a method similar to how you print a newspaper. But removing graphene from copper can be extremely difficult, making an alternate method like this one potentially attractive.
The researchers will now focus on growing larger pieces of graphene and extending the technique to other two dimensional materials. They are also working with industry partners to commercialize their method.