Anomalous solid-like necking of confined water outflow in hydrophobic nanopores

Intrusion of liquid into hydrophobic nanopores has yielded unusual fluid and transport properties that classical theories cannot fully describe, and its extrusion yet remains largely mysterious. Here, we report that the outflow of confined water from hydrophobic nanopores exhibits an anomalous necking phenomenon followed by its breaks, similar to that of solid metal nanowires under uniaxial tension. Molecular dynamics simulations reveal that this solid-like behavior attributes to strong cohesions of water molecules and nanoporous confinements associated with hydrogen-bonding networks and dipole alignments. The extracted elastic modulus and failure strength are quantitatively described by establishing solid-like mechanics scaling laws of outflow deformation and strength. Quasi static experiments on hydrophobic nanopores/water systems were performed and confirmed the scaling laws of both outflow deformation and strength in remarkable agreement with theoretical predictions. This study offers a facile route for probing mechanical and structural properties of nanoconfined liquid by leveraging its unprecedented solid-like outflow behavior.

Automated summary

This study investigates the outflow behavior of confined water in hydrophobic nanopores and reveals its solid-like necking phenomenon and rupture. Molecular dynamics simulations demonstrate that this behavior is attributed to strong interactions between water molecules and the nanoporous confinements. The scaling laws of outflow deformation and strength are quantitatively described and confirmed by experiments, providing a new approach for investigating the mechanical and structural properties of nanoconfined liquid.