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

In extreme confinement, in particular in nanopores, the phase behavior of liquids is dramatically altered, facilitating drying — the formation of a confined vapor phase. Here, the thermodynamics and kinetics of drying are discussed in the light of recent results based on mean field theories and atomistic simulations, clarifying the effect of hydrophobicity, geometry, size, and connectivity of nanopores. The emergence of nanoscale effects not accounted for in macroscopic theories is considered together with the open challenges in the field, which include the presence of dissolved gases and ions in solution. The relevance of such drying phenomena is discussed in different realms; in particular, in biological ion channels, drying of the hydrophobic pore may lead to the block of ionic currents across the membrane, which is known as hydrophobic gating; in solid-state nanoporous materials, drying should be controlled, e.g., in reversed-phase liquid chromatography and in energy applications of heterogeneous lyophobic systems.

A. Giacomello, R. Roth (2020). Adv. Phys.: X, 5, 1817780