A study of nanocapillary filling from ambient temperatures up to those typical of serpentinization examines how the interface between the liquid and the capillary wall, together with evaporation, determines the advance of the liquid front. The work addresses an open problem in the behaviour of fluids confined at the nanometre scale, where surface forces dominate over gravity and classical descriptions of capillarity no longer hold.

The phenomenon investigated, evaporation front pinning, describes how the liquid can become fixed at a particular position within the capillary when mass loss through evaporation exactly balances the capillary supply. This equilibrium is especially relevant under geological conditions such as those of serpentinization, where water interacts with olivine-rich rocks at elevated temperatures and triggers reactions that release hydrogen.

The results show that the interfacial control of filling depends critically on temperature, and that the pinning regime persists from ambient conditions up to the thermal range associated with serpentinization. The transition between free filling and a pinned front is set by the competition between capillary pressure and the evaporation rate inside the channel.

The implications range from understanding fluid migration in the Earth's crust to designing microfluidic devices and membranes that operate at high temperature. Knowing when a nanocapillary fills and when it becomes blocked also allows models of hydrogen production in hydrothermal environments to be refined, a process relevant both to planetary geochemistry and to the search for biosignatures.