Study of the wetting characteristics of water droplet on a heterogeneous pillared surface

We investigated the wetting characteristics of a water droplet on a heterogeneous pillared surface at the nano-scale including contact angle, molecule inflow percentage and density fields and compared them with the wetting characteristics of a water droplet on a homogeneous pillared surface. Molecular dynamics simulations were employed to analyze the wetting behavior of water droplets on surfaces with pillar structures by considering different potential energies including bond, angle, Lennard-Jones and Coulomb to calculate the interacting forces between water molecules and the surface. The heterogeneous surfaces considered had pillars with a different surface energy than the base surface. It was found that the difference in surface energy between the base surface and pillar had little effect on the hydrophobicity of the surface at low pillar heights. However cases with pillar heights over H = 4.24 Å, the pillar surface energy has a larger effect on the molecule inflow percentage with the maximum differences in the range from 33.8% to 47.2% depending on the base surface energy. At a pillar height of H = 16.96 Å, the pillar surface energy has a large effect on the contact angle of the water droplet with the maximum differences in the range from −26.1% to −40.62% depending on the base surface energy. There was a large variation in the contact angle of the droplet as the pillar height increased when there was a large difference in the surface energies between the base and the pillars.