Molecular dynamics modelling of nanodroplet spraying on liquid substrates

Molecular dynamics simulation with a bead-spring model was employed to study the molecular structure and dynamics of perfluoropolyether (PFPE) nano-films in the humid environment. The distribution functions of water, functional end bead, backbone bead were studied to show the nanostructure of PFPE nano-films in humidity. The conformation of PFPE molecules were also studied by calculating the radius of gyration. Water coupled with functional end groups and wall forming characteristic cluster structure was observed. The normalized autocorrelation function of normal modes for entire PFPE chain was studied to extract the characteristic relaxation time. The relaxation times became shorter in the higher humidity, which was consistent with experimental findings. The self-diffusion coefficients of water and PFPE were also calculated to investigate the dynamic property of PFPE films. The molecular dynamics simulation results provided the fundamental understanding of nanostructure and dynamics of PFPE lubricant films, which was critical to optimize the lubricant/overcoat system in HDI. This is an abstract of a paper presented at the 2006 AIChE National Meeting (San Francisco, CA 11/12-17/2006).