Microscopic description of a drop on a solid surface.

Area of Science:

• Physics
• Physical Chemistry
• Materials Science

Background:

• Understanding liquid drop behavior on solid surfaces is crucial for various scientific and industrial applications.
• Existing models often simplify liquid density and temperature effects, limiting their accuracy for nanoscale phenomena.

Purpose of the Study:

• To review and compare two theoretical approaches for describing macro- and nanodrops on diverse solid surfaces.
• To investigate the influence of fluid-fluid and fluid-solid interaction potentials on drop profiles and contact angles.
• To analyze the temperature dependence of contact angles and validate macroscopic models for rough surfaces.

Main Methods:

• Review of a potential energy minimization approach for drop profile and boundary condition derivation.
• Application of nonlocal density functional theory (DFT) to account for liquid density inhomogeneity and temperature effects.
• Investigation of nanodrops on smooth and rough surfaces using canonical ensemble DFT.

Main Results:

• The first approach yields differential equations for drop profiles and boundary conditions, enabling calculation of macroscopic and microscopic contact angles without surface tension.
• DFT accounts for liquid inhomogeneity and temperature, revealing a quasi-universal dependence of contact angle on fluid-solid interaction energy and temperature.
• A critical contact angle value (theta(0)) dictates whether the contact angle increases or decreases with temperature.

Conclusions:

• Both reviewed approaches offer valuable insights into drop behavior on solid surfaces.
• DFT provides a more comprehensive description, especially for nanodrops, by including liquid inhomogeneity and temperature effects.
• The findings validate and refine macroscopic models for drop behavior on rough surfaces and inclined planes.