# Life and death of not so "bare" bubbles

## TL;DR

This study explores how surfactant concentration influences the drainage and rupture behavior of floating bubbles, revealing a transition from foot-initiated to cap-initiated bursting as surfactant levels increase.

## Contribution

It provides new insights into the dependence of bubble rupture location and drainage profile on surfactant concentration, highlighting different rupture mechanisms.

## Key findings

- Drainage profile becomes more plug-like at lower surfactant concentrations.
- Rupture site shifts from near the bubble foot to the top as surfactant concentration increases.
- Different rupture mechanisms are proposed based on surfactant levels, involving marginal regeneration and gravitational drainage.

## Abstract

In this paper, we investigate how the drainage and rupture of surfactant-stabilised bubbles floating at the surface of a liquid pool depend on the concentration of surface-active molecules in water. Drainage measurements at the apex of bubbles indicate that the flow profile is increasingly plug-like as the surfactant concentration is decreased from several times the critical micellar concentration (cmc) to just below the cmc. High-speed observations of bubble bursting reveal that the position at which a hole nucleates in the bubble cap also depends on the surfactant concentration. On average, the rupture is initiated close to the bubble foot for low concentrations (< cmc) while its locus moves towards the top of the bubble cap as the concentration increases above the cmc. In order to explain this transition, we propose that marginal regeneration may be responsible for bubble rupture at low concentrations but that bursting at the apex for higher concentrations is driven by gravitational drainage.