Self-retracting motion of graphite micro-flakes: superlubricity in micrometer scale

TL;DR

This paper investigates the superlubricity-driven self-retracting motion of graphite micro-flakes, revealing scale-dependent effects and defect formation, with implications for micro/nanoelectromechanical systems.

Contribution

It demonstrates superlubricity as the mechanism behind graphite micro-flake self-retraction and links contact states to motion, introducing a model based on polycrystal structure.

Findings

Superlubricity enables self-retracting motion of graphite micro-flakes.

Contact state determines lock-up or retraction behavior.

Defect formation causes loss of self-retractability at larger scales.

Abstract

Through experimental study, we reveal superlubricity as the mechanism of self-retracting motion of micrometer sized graphite flakes on graphite platforms by correlating respectively the lock-up or self-retraction states with the commensurate or incommensurate contacts. We show that the scale-dependent loss of self-retractability is caused by generation of contact interfacial defects. A HOPG structure is also proposed to understand our experimental observations, particularly in term of the polycrystal structure. The realisation of the superlubricity in micrometer scale in our experiments will have impact in the design and fabrication of micro/nanoelectromechanical systems based on graphitic materials.