Investigation of surface wettability behavior using molecular dynamics simulation

Molecular dynamics simulation is one of the computerized computational techniques that can be used to reconstruct the fluid behavior on surfaces from molecular scale. In recent years, many researchers have been interested in investigating the wettability of nanostructures such as graphene and nanoparticles as well as metal surfaces because the control of wettability on surfaces has many applications in various sciences, especially in the manufacture of smart surfaces. Molecular dynamics simulations can be used to complement or confirm experimental data on fluid-bed interaction. In the study of wettability by molecular dynamics simulation approach, the following quantities are usually calculated as described in the present work. Contact angle, surface tension, fluid density profile on the surface, hydrogen bond number, molecular orientation, order parameter, interaction energy between fluid and surface, and diffusion coefficient. Among the above quantities, the two quantities of contact angle and surface tension are also empirically measurable and can provide valuable information about the wettability phenomenon. Due to the amount of bonding force between the water molecules and the adhesion force between the water molecules and the surface, the amount of contact angle and consequently the surface wettability are affected. Where the surface is rough, two main Wenzel and Cassie Baxter models are presented to explain the drop behavior on the surface. In Wenzel´s model, the space between the surface roughness is filled by fluid. On the other hand, fluid behavior in the vicinity of the surface is greatly affected by the nature of the surface and the determination of surface tension plays an important role in understanding the above behaviors.