Superflexibility of graphene oxide

Bending of a thin plate simultaneously involves contraction and stretching of matter relative to a neutral plane, and tensile rigidity dictates the ability of a thin platelet to be bent. If graphene or graphene oxide (GO) were actually behaving as thin platelets, they would display high bending rigidity. Bending measurements for atomic monolayers remain particularly challenging because of their difficult manipulation. We quantitatively measure the GO bending rigidity by characterizing the flattening of thermal undulations in response to shear forces in solution. The bending modulus is found to be 1 kT, which is about two orders of magnitude lower than the bending rigidity of neat graphene. Amazingly, the high stiffness of GO is associated with an unexpected low bending modulus.