Understanding wetting transitions using molecular simulation

The thermophysical and transport properties of fluid at nanoscale, adjacent to the solid surface, are quite different from that of macroscopic level. It has been realized that the fluid behavior can be tuned via modification of surfaces, which can unfold the underlying physics or mechanism of many biochemical processes or phenomena that exist in nature. In this chapter, we mainly emphasize the characteristic equilibrium properties of complex fluids near surfaces. In particular, we investigate different types of surface phase transitions such as layering transition, prewetting transition, and 2D vapor-liquid transition for associating (hydrogen-bond-forming) fluids using molecular simulations. These phases can be altered or controlled using chemically modified surfaces to tune the structure and the stability of the adsorbed layers. In addition, the wetting behavior of different amphiphilic molecules such as water and ethanol and their mixture on smooth and rough surfaces is examined based on the contact angle of the liquid droplet on the surface. Different types of wetting modes such as Cassie-Baxter, Wenzel, and impregnation of a droplet are observed as a function of roughness factor, surface fraction, and composition of the binary mixture. The effect of electric field on the phase transition of water under nanoconfinement is also presented. Further, we also discuss the phase transition and transport properties of 2D thin films.