Dynamic Solidification in Nanoconfined Water Films

TL;DR

This study investigates how nanoconfined water layers exhibit a sharp transition from viscous to elastic behavior as they are compressed to a few molecular layers, revealing significant changes in their mechanical properties.

Contribution

It provides the first direct dynamic nanomechanical measurements showing the transition in mechanical response of water films at molecular confinement levels.

Findings

Mechanical properties change dramatically with dynamic state.

Sharp transition from viscous to elastic response observed.

Relaxation times increase significantly at extreme confinement.

Abstract

The mechanical properties of nanoconfined water layers are still poorly understood and continue to create considerable controversy, despite their importance for biology and nanotechnology. Here, we report on dynamic nanomechanical measurements of water films compressed down to a few single molecular layers. We show that the mechanical properties of nanoconfined water layers change dramatically with their dynamic state. In particular, we observed a sharp transition from viscous to elastic response even at extremely slow compression rates, indicating that mechanical relaxation times increase dramatically once water is compressed to less than 3-4 molecular layers.