Capillarity-Driven Flows at the Continuum Limit

TL;DR

This paper experimentally explores nanoscale capillary-driven flows, demonstrating the applicability and limits of continuum fluid mechanics theories at the nanoscale through innovative experiments involving extreme drying stresses.

Contribution

It introduces a novel experimental platform combining nanoscale pores and microfluidics to test continuum theories at the nanoscale, revealing the breakdown of continuum assumptions.

Findings

Continuum theories hold at the nanoscale within certain limits.

Extreme drying stresses up to 100 MPa can drive nanoflows.

Negative slip length indicates breakdown of continuum assumptions.

Abstract

We experimentally investigate the dynamics of capillary-driven flows at the nanoscale, using an original platform that combines nanoscale pores and microfluidic features. Our results show a coherent picture across multiple experiments including imbibition, poroelastic transient flows, and a drying-based method that we introduce. In particular, we exploit extreme drying stresses - up to 100 MPa of tension - to drive nanoflows and provide quantitative tests of continuum theories of fluid mechanics and thermodynamics (e.g. Kelvin-Laplace equation) across an unprecedented range. We isolate the breakdown of continuum as a negative slip length of molecular dimension.