Design of Frictionless Interfaces for Moiré Layers

Ultralow friction offers great potential for energy-efficient applications. However, the superlubric sliding of a flake is often plagued by persistent finite friction arising from incomplete moiré tiles at flake edges. To tackle this challenge, we develop a theory of structural frictionless interface based on moiré geometry. Our theory predicts the existence of a directional frictionless interface, which can further evolve to two kinds of all-direction frictionless interfaces, even when the total flake area is not a multiple of the size of a complete moiré tile. Before reaching the frictionless state, friction scales with flake area via a geometry-dependent proportionality factor that encodes frictionless directions, agreeing with large-scale molecular dynamics simulations for both homogeneous or heterogeneous interfaces. Our theory further paves the way for designing frictionless motions in double-interface nanoconfinement channels. Our work provides insights into the creation of structural frictionless interfaces for future advancements in nanoscale tribology and nanoconfinement transport.