Chain-reaction cascades in surfactant monolayer buckling

TL;DR

This study investigates the dynamic folding behavior of surfactant monolayers at the water-air interface, revealing cascade-like folding events driven by cooperative, autocatalytic processes, with detailed statistical analysis of the folding dynamics.

Contribution

It provides the first detailed statistical characterization of cascade-like folding events in surfactant monolayers, highlighting the autocatalytic nature of the instability.

Findings

Folding events follow broad magnitude distributions.

Angles and durations of folds have narrow, non-Gaussian distributions.

Folding cascades suggest an autocatalytic, cooperative process.

Abstract

Certain surfactant monolayers at the water-air interface have been found to undergo, at a critical surface pressure, a dynamic instability involving multiple long folds of micron width. We exploit the sharp monolayer translations accompanying folding events to acquire, using a combination of fluorescence microscopy and digital image analysis, detailed statistics concerning the folding dynamics. The motions have a broad distribution of magnitudes and narrow, non-Gaussian distributions of angles and durations. The statistics are consistent with the occurrence of cooperative cascades of folds, implying an autocatalytic process uncommon in the context of mechanical instability.