Stability of Surface Nanobubbles: A Molecular Dynamics Study

TL;DR

This study uses Molecular Dynamics simulations to investigate the stability of surface nanobubbles, revealing that contact line pinning and gas oversaturation are key to their stability and behavior.

Contribution

The paper demonstrates how contact line pinning and gas oversaturation contribute to nanobubble stability, confirming theoretical predictions through molecular dynamics simulations.

Findings

Pinning of the contact line stabilizes nanobubbles with oversaturated gas.

Equilibrium contact angle follows theoretical relation with oversaturation.

Undersaturation leads to nanobubble dissolution with stick-jump dynamics.

Abstract

The stability and growth or dissolution of a single surface nanobubble on a chemically patterned surface are studied by Molecular Dynamics (MD) simulations of binary mixtures consisting of Lennard-Jones (LJ) particles. Our simulations reveal how pinning of the three-phase contact line on the surface can lead to the stability of the surface nanobubble, provided that the concentration of the dissolved gas is oversaturated. We have performed equilibrium simulations of surface nanobubbles at different gas oversaturation levels $\zeta>0$. The equilibrium contact angle $\theta_e$ is found to follow the theoretical result of Lohse and Zhang (Phys. Rev. E 2015, 91, 031003(R)), namely $\sin\theta_e = \zeta L/L_c$, where L is the pinned length of the footprint and $L_c = 4\gamma/P_0$ a capillary length scale, with $\gamma$ the surface tension and $P_0$ the ambient pressure. For undersaturation $\zeta<0$ the surface nanobubble dissolves and the dissolution dynamics shows a "stick-jump" behaviour of the three-phase contact line.