The friction properties of an ultrathin confined water film

An ultrathin water film confined between two substrates in moving contact is studied using Langevin molecular dynamics with coordinate- and velocity-dependent damping coefficient. The correlations between the structure of the water lubricant film and its frictional properties are found in a wide range of applied loads and for various strengths of interactions between water and surfaces. A self-organization of the film into a low-friction state under driving is observed to occur. Surprisingly, it is found that the “hydrophilic” surfaces exhibit a lower friction than the “hydrophobic” ones. The viscosity of the confined water estimated from the simulations is in a good agreement with the experimental value.