# The effect of boundary slippage and nonlinear rheological response on flow of nanoconfined water

## TL;DR

This study investigates how boundary slippage and nonlinear rheology influence nanoconfined water flow, revealing that wettability and shear-thinning behavior significantly affect transport properties at the nanoscale.

## Contribution

It provides experimental evidence linking surface wettability and nonlinear rheology to boundary slip and flow behavior in nanoconfined water.

## Key findings

- Flow is non-Newtonian under nanoconfinement.
- Boundary slip occurs on non-wetting surfaces with nanometer slip lengths.
- Wetting surfaces exhibit no-slip boundary conditions.

## Abstract

The flow of water confined to nanometer-sized pores is central to a wide range of subjects from biology to nanofluidic devices. Despite its importance, a clear picture about nanoscale fluid dynamics is yet to emerge. Here we measured dissipation in less than 20 nm thick water films and it was found to decrease for both wetting and non-wetting confining surfaces. The fitting of Carreau-Yasuda model of shear thinning to our measurements implies that flow is non-Newtonian and for wetting surfaces the no-slip boundary condition is valid. On the contrary, for non-wetting surfaces boundary slippage occurs with slip lengths of the order of few nm. The findings suggest that both, the wettability of the confining surfaces and nonlinear rheological response of water molecules under nano-confinement play a dominant role in transport properties.