Bubble formation in nanopores: a matter of hydrophobicity, geometry, and size

This review focuses on the phase behaviour of liquids in nanoscale confinement, which promotes drying by a combination of hydrophobicity, small size, and high degree of confinement. In these conditions, the vapour phase can form at exceptionally large pressures or low temperatures as compared to bulk vaporisation, giving rise to the unexpected formation of bubbles. A general framework is introduced which allows to understand the main effects of confinement on the thermodynamics and on the kinetics of drying. The relevance of such phenomena is discussed in the realm of biological nanopores, specifically ion channels, and in nanoporous materials. The emergence of nanoscale effects not accounted for in macroscopic theories is discussed together with the open challenges in this rapidly expanding field.