Graphene’s Newfound Strength

Graphene is one of the strongest known materials on the microscale. But some processes that could economically produce large quantities of graphene, such as chemical vapor deposition (CVD), create a polycrystalline version that is weak at the grain boundaries, the interfaces between variously oriented crystal regions that make up the bulk material. That weakness is a result of the processing, not an inherent characteristic of the material, report Gwan-Hyoung Lee, Ryan C. Cooper, Jeffrey W. Kysar, and James Hone of Columbia University and coworkers (Science 2013, DOI: 10.1126/science.1235126). Graphene is usually grown on copper foil, which must be etched away, and is transferred using a polymer support that is then removed. Both steps weaken the grain boundaries, making the material an order of magnitude weaker than pristine graphene, which has no grain boundaries. The group swapped the etching chemical and transfer method for gentler alternatives and, using an atomic force microscopy method called nanoindentation, found that the resulting films were nearly as strong as pristine graphene. With this information in hand, the group says CVD-prepared graphene can be used as “a large-area, high-strength material for flexible electronics” and in other applications.