ABSTRACT
In this chapter, a liquid drop on a smooth or rough planar solid surface was examined on the basis of a microscopic nonlocal density functional theory in canonical ensemble. The main idea was to consider drop-like nonuniform density distribution in a closed volume of fluid in contact with solid and from this distribution identify and analyze the drop profile. The obtained results for contact angle θ which drop profile makes with the solid surface are compared with predictions of classical theories for macroscopic drops and similarities and differences between them are analyzed. Among the results, one can mention a simple linear dependence of θ on the fluid-solid interaction parameter εfs for a drop on a smooth surface, the increase of θ with increasing roughness for a drop on hydrophilic rough surface (behavior opposite to predictions of classical theory), analysis of θ for a drop of magnetic fluid, analysis of hidden roughness, and calculation of the sticking force for the drop on an inclined surface.
