Labyrinthine water flow across multilayer graphene-based membranes: molecular dynamics versus continuum predictions

TL;DR

This study compares molecular dynamics simulations and continuum models to predict water flow through multilayer graphene membranes, demonstrating continuum models' effectiveness even at nanoscales and challenging the notion of hydrodynamics breakdown.

Contribution

It provides a validated continuum modeling approach for water permeance in graphene membranes, bridging molecular and macroscopic descriptions.

Findings

Continuum models accurately predict permeability at nanoscales.

Hydrodynamics remains valid despite extreme confinement.

Results serve as a benchmark for experimental data.

Abstract

In this paper we investigate the hydrodynamic permeance of water through graphene-based membranes, inspired by recent experimental findings on graphene-oxide membranes. We consider the flow across multiple graphene layers having nanoslits in a staggered alignment, with an inter-layer distance ranging from sub- nanometer to a few nanometers. We compare results for the permeability obtained by means of molecular dynamics simulations to continuum predictions obtained by using the lattice Boltzmann calculations and hydrodynamic modelization. This highlights that, in spite of extreme confinement, the permeability across the graphene-based membrane is quantitatively predicted on the basis of a continuum expression, taking properly into account entrance and slippage effects of the confined water flow. Our predictions refute the breakdown of hydrodynamics at small scales in these membrane systems. They constitute a benchmark to which we compare published experimental data.