Macroscale superlubricity enabled by rationally designed MoS2-based superlattice films

Superlubricity, a state with nearly zero friction, is highly desirable for many engineering applications, yet its implementation has so far been constrained due to limited contact size, strict environmental requirements, and poor lifetime. By designing superlattice films with alternating molybdenum disulfide (MoS2) and tungsten carbide layers, we report that long-term macroscale superlubricity (friction coefficient of 0.006) can be achieved in mild vacuum (∼10−3 Pa) with robust environmental adaptability. Such extraordinary performance is enabled when the fine structure of the bilayer unit is rationally controlled to yield numerous incommensurate nanocontacts between highly ordered MoS2 and metal-oxide nanoparticles spontaneously formed during tribological sliding. Our analysis indicates that the ceramic phase with precisely controlled thickness is critical for superlubricity by helping to stiffen the film, facilitate the preferential growth of crystalline MoS2, and produce lubricous nanoparticles. The superlattice architecture offers a general route for designing MoS2-based materials toward long-lifetime, self-rejuvenating macroscale superlubricity.