Wetting behavior of water droplet on solid surfaces in solvent environment: A molecular simulation study

In this work, molecular dynamics simulations were performed to investigate the wetting behavior of solid surfaces in the presence of model solvent. Three kinds of solid surfaces were considered with different hydrophilicities. We simulated the microscopic contact angles of water droplet on the solid surfaces by analyzing the phase boundary locus at the water/solvent/solid interfaces. It was observed that the contact angle generally increases with the surrounding solvent density. This behavior is qualitatively consistent with the available limited experimental observation. However, at very high solvent density, the water droplet was found to separate with the hydrophobic surface. This simulation study provides direct microscopic evidence for the effect of solvent on the wettability of a solid substrate. The wetting phenomenon was interpreted in terms of free energy analysis. It was shown that the wetting behavior is determined by a competition effect between the water–solvent interaction and the surface–water interaction.