Charge-induced ultralow friction

Abstract

Abstract Reaching near-zero friction is one of the jewels on the crown of tribology, and structural lubricity is a crucial mechanism to achieve it. Previous works focus mainly on the structural lubricity at incommensurate crystalline interfaces. However, realizing such interfaces on a large scale without defects and contaminations is a formidable challenge. Here, we report a charge-induced robust macroscale superlubricity between single crystal graphite and atomically flat surfaces in the ambient condition. We transferred single crystal graphite flakes on Si3N4 balls and used them to measure the friction properties on pristine and charged atomically flat surfaces such as 300 nm SiO2/Si and sapphire. We found that the surface charge can dramatically reduce the coefficient of friction between graphite and substrates by two orders of magnitude to 10-4, and the sliding is wearless even under harsh contact conditions (~ 1.1 GPa center pressure and > 100 m). We demonstrate that the surface charge is critical in achieving superlubricity because it can reduce adhesion between graphite and substrate surfaces and make the substrate surfaces resistant to contaminations. Our method offers a ready-to-use solution to superlubricity alternative to achieve incommensurate crystalline interfaces. Thus, it can reduce the difficulty of realizing macroscale superlubricity for applications.