A unified description of hydrophilic and superhydrophobic surfaces in terms of the wetting and drying transitions of liquids

TL;DR

This paper provides a comprehensive theoretical framework for understanding wetting and drying phase transitions on surfaces, revealing new classes of surface phase diagrams and their dependence on interaction ranges and temperature.

Contribution

It introduces a unified description of wetting and drying transitions, uncovering previously unrecognized classes of surface phase diagrams and their differences from simple models.

Findings

Different classes of surface phase diagrams depend on interaction ranges and temperature.

Drying and wetting transitions differ even near the bulk critical point.

Superhydrophobic behavior is more observable at high temperatures.

Abstract

Clarifying the factors that control the contact angle of a liquid on a solid substrate is a long-standing scientific problem pertinent across physics, chemistry and materials science. Progress has been hampered by the lack of a comprehensive and unified understanding of the physics of wetting and drying phase transitions. Using various theoretical and simulational techniques applied to realistic fluid models, we elucidate how the character of these transitions depends sensitively on both the range of fluid-fluid and substrate-fluid interactions and the temperature. Our calculations uncover previously unrecognised classes of surface phase diagram which differ from that established for simple lattice models and often assumed to be universal. The differences relate both to the topology of the phase diagram and to the nature of the transitions, with a remarkable feature being a difference between drying and wetting transitions which persists even in the approach to the bulk critical point. Most experimental and simulational studies of liquids at a substrate belong to one of these previously unrecognised classes. We predict that while there appears to be nothing particularly special about water with regard to its wetting and drying behavior, superhydrophobic behavior should be more readily observable in experiments conducted at high temperatures than at room temperature.