Knudsen gas provides nanobubble stability

TL;DR

This paper presents a model explaining the exceptional stability of surface nanobubbles by considering the gas as Knudsen type, which induces a local flow that prevents dissolution, supported by experimental validation.

Contribution

The study introduces a novel Knudsen gas-based model for nanobubble stability, predicting flow dynamics and size limits consistent with experimental observations.

Findings

Predicted water jet speed of ~3.3 m/s matches measured ~2.7 m/s.

Model explains nanobubble stability against dissolution.

Provides an upper size bound for nanobubbles consistent with data.

Abstract

We provide a model for the remarkable stability of surface nanobubbles to bulk dissolution. The key to the solution is that the gas in a nanobubble is of Knudsen type. This leads to the generation of a bulk liquid flow which effectively forces the diffusive gas to remain local. Our model predicts the presence of a vertical water jet immediately above a nanobubble, with an estimated speed of $\sim3.3\,\mathrm{m/s}$, in good agreement with our experimental atomic force microscopy measurement of $\sim2.7\,\mathrm{m/s}$. In addition, our model also predicts an upper bound for the size of nanobubbles, which is consistent with the available experimental data.