Negative area-dependent nanoscale friction of annular graphene sheets

The influence mechanisms of the contact area on the sliding friction behavior are still not entirely clear, and determining the intrinsic correlation between friction and the contact area at the nanoscale remains a challenge. In this study, the area-dependent friction behavior is investigated based on the model of an annular graphene flake sliding on a supported graphene substrate via molecular dynamics simulations. The results demonstrate that the friction force decreases with the increasing flake area, i.e., the nanoscale friction is inversely correlated with the contact area. This contradicts the everyday experience, wherein an increase in the contact area leads to an increase in friction. The more pronounced edge effects and elastic deformation are considered the main reasons for the larger friction force of a smaller flake on the substrate. The study results are useful for comprehensively understanding the friction behavior of two-dimensional materials and extending their application fields.