Molecular Dynamics Simulation of Droplets On a Nanopatterned Solid Surface

We use molecular dynamics simulations to study the wetting of Lennard-Jones cylindrical droplets on a surface patterned with nanogrooves. We find that the surface topography, intrinsic contact angle, size, and initial position of the droplet strongly affect the wetting states and corresponding contact angles. Depending on the topographical parameters characterizing the surface, multiple wetting modes, separated by free-energy barriers, can be observed.  By scaling the surface topography parameters with droplet size, we find that the preferred wetting modes become independent of droplet size at the nano-scale.  This result is in agreement with a mathematical model for the droplet free energy at small Bond numbers, where the effects of gravity are insignificant. We construct phase diagrams of the preferred wetting modes and find that these are in good agreement with a mathematical model for the droplet free energy.