Single-Bubble Dynamics in Nanopores: Transition Between Homogeneous and Heterogeneous Nucleation

TL;DR

This study explores how bubble nucleation inside nanopores transitions from homogeneous to heterogeneous as pore size increases, using thermodynamic modeling to understand and predict bubble behavior for nanoscale applications.

Contribution

The paper introduces a thermodynamic model that explains the transition between homogeneous and heterogeneous bubble nucleation in nanopores based on pore size and free-energy considerations.

Findings

Nucleation regime shifts from homogeneous to mixed as pore diameter increases.

A transition barrier based on free-energy costs is identified.

Experimental bubble behavior aligns with thermodynamic predictions.

Abstract

When applying a voltage bias across a thin nanopore, localized Joule heating can lead to single bubble nucleation, offering a unique platform for studying nanoscale bubble behavior, which is still poorly understood. Accordingly, we investigate bubble nucleation and collapse inside solid-state nanopores filled with electrolyte solutions and find that there exists a clear correlation between homo/heterogeneous bubble nucleation and the pore diameter. As the pore diameter is increased from 280 nm to 525 nm, the nucleation regime transitions from predominantly periodic homogeneous nucleation to a non-periodic mixture of homogeneous and heterogeneous nucleation. A transition barrier between the homogeneous and heterogeneous nucleation regimes is defined by considering the relative free-energy costs of cluster formation. A thermodynamic model considering the transition barrier and contact-line pinning on curved surfaces is constructed, which determines the possibility of heterogeneous nucleation. It is shown that the experimental bubble generation behavior is closely captured by our thermodynamic analysis, providing important information for controlling the periodic homogeneous nucleation of bubbles in nanopores.