Anomalous interplay of slip, shear and wettability in nanoconfined water

Abstract

Slip of liquid over nanometer scales is traditionally believed to be augmented with interfacial shear. In sharp contrast to this intuitive paradigm, here we show that a reverse of this phenomenon may also be possible, by exploiting a rich and non-trivial interplay between interfacial wettability and shear distribution in nano-confined water. This may be attributed to the complex overlapping effect of the local hydrodynamic fields imposed by the opposing boundaries, in the case of highly confined water molecules. The net effect culminates in the form of intriguing molecular layering that can by no means be intuitively estimated, as unveiled from the present molecular dynamics simulations. The consequent complex nature of the interfacial friction is observed to depend not only on the chemical and physical signature of the interface but also on the distribution of the shear rate. We also provide a simple continuum-based theory, in an effort to capture the essential aspects of the underlying physico-chemical interactions. These results are likely to open up new windows for control of slippery and sticky flows in nanofluidic channels.