  This work revisits capillary filling dynamics in the regime of nanometric to
subnanometric channels. Using molecular dynamics simulations of water in carbon
nanotubes, we show that for tube radii below one nanometer, both the filling
velocity and the Jurin rise vary non-monotonically with the tube radius.
Strikingly, with fixed chemical surface properties, this leads to
confinement-induced reversal of the tube wettability from hydrophilic to
hydrophobic for specific values of the radius. By comparing with a model liquid
metal, we show that these effects are not specific to water. Using
complementary data from slit channels, we then show that they can be described
using the disjoin-ing pressure associated with the liquid structuring in
confinement. This breakdown of the standard continuum framework is of main
importance in the context of capillary effects in nanoporous media, with
potential interests ranging from membrane selectivity to mechanical energy
storage.
