Predicting the Dynamics of Wetting from the Fluctuations of Forces at an Equilibrium Solid-Liquid Interface

We use molecular dynamics (MD) and Lennard-Jones potentials to model a liquid bridge between two solid surfaces and apply the fluctuation-dissipation theorem to compute the friction between the liquid and the solid walls at equilibrium. We find that the frictions obtained per unit length of the interface are the same as the coefficients of contact-line friction found by applying the molecular-kinetic theory (MKT) of dynamic wetting to the dynamic contact angles found in MD simulations of spreading liquid drops and Couette flow in a liquid bridge using identical methods and potentials. Our results show the same dependence on the strength of solid-liquid interactions and the equilibrium contact angle. Combined with the lattice spacing of the solid surface, the results allow one to extract the key MKT parameters necessary to predict the full velocity-dependence of the microscopic dynamic contact angle. These findings confirm a common underlying mechanism for contact-line friction and slip at solid liquid interfaces.