Interfacial control and evaporation pinning of nanocapillary filling from ambient to serpentinization temperatures

Abstract Fluid transport in nanometer-scale channels underlies nanofluidic technologies and geological systems, yet measured capillary filling rates in hydrophilic channels are often far slower than classical theory predicts. Here we show, using a coupled flow model based on classical density functional theory combining hydrodynamics, electrokinetics and capillarity, that electrokinetic resistance and locally elevated viscosity near the channel walls jointly suppress flow, capturing the measured slowdown across independent experiments. At higher temperatures relevant to serpentinization (around 200 degrees Celsius), the model predicts a regime of evaporation-driven pinning: once relative humidity falls below saturation, classical capillary scaling breaks down and evaporation, orders of magnitude faster than at ambient conditions, balances capillary inflow and pins the meniscus inside the channel. Depending on wettability, humidity and channel length, transport may continue through thin liquid films and vapor migration. These predictions await experimental testing but identify a high-temperature flow regime, to our knowledge not previously described in nanochannels, relevant to nanodevice design, subsurface fluid modeling, and geologic hydrogen generation.