Robust microscale structural superlubricity between graphite and nanostructured surface

Abstract

Structural superlubricity (SSL), a state of nearly zero friction and no wear between two contacted solid surfaces, brought a dawn for the revolutionary solution of friction and wear problems. Recently, SSL was realized between microscale graphite flake with two dimensional single-crystalline surface and various non-van der Waals materials, which greatly broadens its application range. However, the SSL state has a certain probability of failure due to the edge defects of graphite flake. Here, we achieve robust SSL state between microscale graphite flakes and nanostructured silicon surfaces under ambient condition. We find that the friction is always less than 1 μN, the differential friction coefficient is on the order of 10-4, without observable wear. Detailed characterization and simulation show that this is attributed to the edge warping of graphite flake on the nanostructured surface under concentrated force, which eliminate the edge interaction between the graphite flake and the substrate. This study proves that a graphite flake with single crystal surface without edge contact with the substrate can universally realize robust SSL state with any non-van der Waals materials in the atmosphere, which reduce the roughness requirements of SSL technology and provides a new method for SSL technology to generally apply in the atmospheric environment.