MIT has combined a roll-to-roll approach — a common industrial approach for continuous processing of thin foils — with the common graphene-fabrication technique of chemical vapor deposition, to manufacture high-quality graphene in large quantities and at a high rate.
The system consists of two spools, connected by a conveyor belt that runs through a small furnace. The first spool unfurls a long strip of copper foil, less than 1 centimeter wide. When it enters the furnace, the foil is fed through first one tube and then another, in a "split-zone" design.
While the foil rolls through the first tube, it heats up to a certain ideal temperature, at which point it is ready to roll through the second tube, where the scientists pump in a specified ratio of methane and hydrogen gas, which are deposited onto the heated foil to produce graphene.
"Graphene starts forming in little islands, and then those islands grow together to form a continuous sheet," Hart says. "By the time it's out of the oven, the graphene should be fully covering the foil in one layer, kind of like a continuous bed of pizza."
The researchers found that they were able to feed the foil continuously through the system, producing high-quality graphene at a rate of 5 centimeters per minute. Their longest run lasted almost four hours, during which they produced about 10 meters of continuous graphene.