On the role of surfactants in emulsions and foams

This perspective article is centered around my work related to surfactant science. The field is multidisciplinary, linked to physics, chemistry and biology. It is part of the field of soft matter and is well connected to industrial applications. My particular expertise deals with liquid surfaces, an area that expanded considerably with the advent of miniaturization, i.e., when surfaces begin to matter. I started my research with surface light scattering and surface rheology investigations. The light scattering technique allows measurements of low interfacial tension systems, and led me to investigate microemulsions. After this work, I used my knowledge in surface rheology to investigate emulsions and foams, which are not thermodynamically stable, in contrast with microemulsions. The work is still ongoing, in particular to reach a better understanding of coalescence of bubbles and drops. I will show how interesting it is to use knowledge on surface layers at macroscopic interfaces to better understand microemulsions, emulsions and foams. I conclude with considerations on the perspectives of the research field.