In an effort to develop superstrong lightweight materials, others have used carbon nanotubes. And the new graphene-oxide paper is not as strong as carbon-nanotube films, Geim says. “The advantage of materials made from carbon nanotubes is they’re much tougher, because they entangle like spaghetti,” he says. “When you’re dealing with flat sheets, they entangle very little and are breakable.”
But the graphene-oxide paper has other key advantages. Graphite is a cheap raw material, and the filtration method is simple and leads to lots of graphene. Most important, the Northwestern researchers’ work opens up a way to manipulate graphene sheets and make paperlike materials with different properties.
When Ruoff and his colleagues oxidize graphene into graphene oxide, for instance, the carbon-based material goes from being an electrical conductor to being an insulator. Ruoff says that he can alter graphene’s chemistry in other ways to change its electrical properties and make it an insulator, a conductor, or even a semiconductor.
That electrical versatility combines with an ultrastrong material has some observers excited. “They haven’t used any tough glue between the [graphene platelets],” Geim says. “I expect very, very tough materials if a proper glue between graphene is used.”