Microscopic Wetting at Nanostructured Surface: A Molecular Dynamics Study

Wettability of the solid surface is a very important property in the micro/nanoscale thermal fluidic systems. In this study, molecular dynamics simulations were carried out to study the microscopic wetting characteristics at the nanostructured surface and the contacting mode in the vicinity of the solid-liquid-vapor interface. A pure liquid nanodroplet was placed on a solid surface in a shape of molecular-scale unevenness with different height and spacing. The wettability of the solid-liquid interface was examined with evaluating the contact angles at the three-phase interface and the liquid-solid contacting area ratio. The results of the measured contact angles demonstrated that the nanostructures could strengthen the hydrophobic properties for a partial wetting condition, while it was insignificant in a completely wetting case. Furthermore, we compared the results of molecular dynamics (MD) simulations to the classical descriptions of Wenzel’s model and Cassie-Baxter’s model. Significant discrepancy among the results was found and a new model of contact angle in consideration of liquid filling ratio among nanostructures was proposed.