Review of the role of surfactant dynamics in drop microfluidics

Surfactants are employed in microfluidic systems not just for drop stabilisation, but also to study local phe-nomena in industrial processes. On the scale of a single drop, these include foaming, emulsification and stability of foams and emulsions using statistically significant ensembles of bubbles or drops respectively. In addition, surfactants are often a part of a formulation in microfluidic drop reactors. In all these applications, surfactant dynamics play a crucial role and need to be accounted for. In this review, the effect of surfactant dynamics is considered on the level of standard microfluidic operations: drop formation, movement in channels and coa-lescence, but also on a more general level, considering the mechanisms controlling surfactant adsorption on time -and length-scales characteristic of microfluidics. Some examples of relevant calculations are provided. The ad-vantages and challenges of the use of microfluidics to measure dynamic interfacial tension at short time-scales are discussed.

Automated summary

Surfactants are used in microfluidic systems to stabilize drops and study phenomena in industrial processes. The dynamics of surfactants play a crucial role in drop formation, movement in channels, coalescence, and surfactant adsorption. This review discusses the effects of surfactant dynamics on microfluidic operations and the advantages and challenges of measuring dynamic interfacial tension using microfluidics.