Superlubricity

Superlubricity is a regime of motion in which the friction between sliding solid surfaces is extraordinarily small, often accompanied by greatly reduced wear. It is typically studied at the micro- to nanoscale, where interfacial interactions can be controlled and characterized.

A key mechanism is structural superlubricity, which occurs when contacting crystalline surfaces are incommensurate, meaning their atomic lattices do not match. In such arrangements the lateral forces contributed by the atoms average to near zero, creating a very smooth energy landscape with suppressed stick-slip and low energy barriers to sliding.

Layered materials such as graphene and graphite, hexagonal boron nitride, and transition-metal dichalcogenides like MoS2, often exhibit structural superlubricity under appropriate conditions. Experiments using atomic force microscopy and nanoscale contact tests have demonstrated ultra-low friction for clean, well-oriented interfaces; some observations extend to micro-scale devices in controlled environments.

Real-world realization remains challenging. Friction and wear can rise due to contamination, chemical reactions, surface roughness, temperature fluctuations, and changes in orientation during sliding. Achieving stable, long-duration superlubricity at macroscopic scales is an active area of research.

Potential applications include reducing wear in MEMS and NEMS, precision positioning systems, and advanced coatings designed to maintain low friction under specific conditions. The concept is one of ongoing research into material design, surface treatment, and interface engineering to extend ultra-low friction regimes beyond laboratory demonstrations.