Dynamics of nanoscale bubbles growing in a tapered conduit

TL;DR

This paper models the growth and shape of nanoscale bubbles in a tapered confined environment, explaining experimental observations of slow growth and tear-drop shapes through a migration mechanism based on Blake-Haynes theory.

Contribution

It introduces a theoretical model for nanoscale bubble dynamics in tapered channels, incorporating a migration mechanism and explaining shape and growth rate differences due to confinement.

Findings

Growth rates are significantly slower under confinement.

Tapered channels and contact line pinning produce tear-drop shaped bubbles.

Model aligns with experimental observations of bubble shapes and growth.

Abstract

We predict the dynamics and shapes of nanobubbles growing in a supersaturated solution confined within a tapered, Hele-Shaw device with a small opening angle $\Phi \ll 1$. Our study is inspired by experimental observations of the growth and translation of nanoscale bubbles, ranging in diameter from tens to hundreds of nanometers, carried out with liquid-cell transmission electron microscopy. In our experiments, the electron beam plays a dual role: it supersaturates the solution with gaseous radiolysis products, which lead to bubble nucleation and growth, and it provides a means to image the bubbles in-situ with nanoscale resolution. To understand our experimental data, we propose a migration mechanism, based on Blake-Haynes theory, which is applicable in the asymptotic limits of zero capillary and Bond numbers and high confinement. Consistent with experimental data, our model predicts that in the presence of confinement, growth rates are orders of magnitude slower compared to a bubble growing in the bulk and that the combination of a tapered channel and contact line pinning create tear-drop shaped bubbles.