Molecular dynamics simulations of lubricant spreading on lubricant-patterned substrates

The spreading of nonfunctional perfluoropolyether (PFPE) on PFPE-patterned substrates is examined using molecular dynamics simulations. During the spreading process, mobile molecules will encounter, pass by, and embrace the bonded ones. The movement of mobile molecules is hindered by the bonded ones. The spreading exhibits a slow evolution with time, a steep profile with a precursor film from a side view and a complicated profile from a top-down view. The atomic-scale mechanism is analyzed by the driving term, such as the van der Waals interaction and surface diffusion, and the resistance term, such as the interaction between bonded and mobile molecules or, furthermore, the combined interaction from the adjacent bonded molecules. Besides, the spreading profiles of PFPE on PFPE-patterned substrates with different coverage ratios are compared, which indicate that the coverage ratio has significant effects on the PFPE spreading behavior.