Spreading Characteristics of Molecularly Thin Lubricant on Surfaces With Groove-Shaped Textures: Monte Carlo Simulation and Measurement Using PFPE Film

Spreading characteristics of molecularly thin lubricant on a grooved surface have been studied numerically by Monte Carlo simulations and compared with measurements obtained by perfluoropolyether (PFPE) thin film spreading on a solid surface with minute grooves. In the simulations, by incorporating the interactions between molecules and the side surfaces of a groove, the Monte Carlo method based on the Ising model was extended to the case of a surface with grooves and applied to simulate the spreading of non-polar lubricant inside a groove. Compared with the spreading on a smooth surface, lubricant spreads rapidly inside a groove, indicating an acceleration of the spreading along the groove. In the experiments, lubricant spreading on a surface with groove-shaped textures was measured by making use of the phenomenon in which diffracted light decreases or vanishes in the lubricant-covered region. Based on the results showing lubricant spreading predominantly along the groove, the accelerating effect obtained in the simulations is well confirmed by the measurements.