Credit: © 2008 AAAS

Even in a controlled environment it is hard to attain perfection in a material. This is because of the structural defects and flaws created during synthesis and processing. As a result, the mechanical properties of a material rarely exhibit their inherent values, and it is difficult to measure the intrinsic strength of a pristine material. Now, James Hone and colleagues1 at Columbia University have caught sight of this ideal with measurements on a single layer of graphene.

The researchers used an atomic force microscope to explore the elastic properties and intrinsic breaking strength of a layer of graphene that had been suspended over open holes. The holes were patterned into a silicon substrate and graphite flakes deposited over the top. Once areas of monolayer graphene had been identified, measurements were made by indenting the centre of a covered hole with the diamond-tipped atomic force microscope.

The strength of graphene was measured by pushing the suspended layer to breaking. The results suggest that the area of graphene near the microscope tip is free from defects, and hence the maximum stress the material can bear corresponds to its intrinsic strength. The experiments confirm graphene to be the strongest material ever measured.