Slip flow regimes in nanofluidics: a universal superexponential model

TL;DR

This paper introduces a universal superexponential model for nanofluidic slip flow that accurately explains experimental flow enhancements in nanotubes, bridging the gap between simulations and measurements, and providing insights into nanoscale transport mechanisms.

Contribution

The study presents a generic continuum slip flow model that accounts for experimental flow enhancements in nanotubes, explaining a wide range of data with finite interfacial energy variations.

Findings

Model explains experimental flow enhancement ratios across 140 cases.

Predictions closely match experimental data for most cases.

Provides insights into effects of nanotube material and surface properties.

Abstract

Many experiments have shown large flow enhancement ratios (up to 10^5) in carbon nanotubes (CNT) with diameters larger than 5nm. However, molecular dynamics simulations have never replicated these results maintaining a three-order-of-magnitude gap with measurements. Our study provides a generic model of nanofluidics for continuum slip flow (diameter>3nm) that fills this significant gap and sheds light on its origin. Compared to 140 literature cases, the model explains the entire range of experimental flow enhancements by changes of nanotube diameters and finite variations of interfacial energies. Despite large variations of flow enhancement ratios spanning 5 orders of magnitude in experimental results, the ratio between these data and corresponding model predictions approaches unity for the majority of experiments. The role of viscous entrance effects is discussed. The model provides insight into puzzling observations such as differences of CNTs and boron nitride nanotubes, the slip on low-contact-angle surfaces and massive functionalization effects. This study could advance our understanding of nano-scale transport mechanisms and aid the design of tailored nanomembranes.