First of all, the extreme mechanical strength of graphene suppresses material wear. For example, Lee et al.[5] tested the mechanical properties of graphene and confirmed it to be one of the strongest materials ever measured. For their study, the authors used free-standing graphene membranes and analyzed them with a diamond atomic force microscopy (AFM) probe, which allowed measuring the breaking strength. The measured strength of defect-free graphene sheet corresponds to a Young's modulus of 1 TPa. The breaking force depends on the tip radius, not the diameter of the membrane. Moreover, it was shown recently that the grain boundaries do not affect the overall strength of graphene [6]