Post-doc Fellowship

Soap films are of great interest, either as nanometer-thick membranes or as foam
building blocks. It is therefore essential to understand, and even control, their stability. The
formulation of soapy solutions is essential to adjust this stability by modifying the
thermodynamics and the mechanical properties of the liquid/air interfaces. Furthermore,
numerous studies prove that the structure and dynamics of adsorbed surfactants are crucial
to understand these macroscopic changes. If the link between micro and macro scale is
commonly admitted, it is still not fully revealed. Direct experimental investigations of the
adsorbed layer structure and its role on the macroscopic properties of the interface, and
particularly soap film stability, are still lacking notably because of the lack of surface-specific
tools which are also sensitive to the
spatial organization of the surfactants.
In that context, SOLSTICE ANR project
aims to develop a molecular description
of soap film stability, with Second
Harmonic Generation (SHG) experiments.
It consists on the conversion of two
photons at a fundamental frequency ω to
a photon at the harmonic frequency 2ω.
Since this elementary process is
forbidden in centrosymmetric media, this
technique is thus a tool of choice to probe interfaces and then tackle questions addressed in
SOLSTICE project.
Previous studies have shown that such technique is sensitive to the concentration and
organization of amphiphile molecules, and among them surfactants, at interface or in bulk. In
this project, we plan to probe the surfactant organization and dynamics at interface on single
interface and on soap film. The post-doc will upgrade an existing setup and perform SHG
experiments on soapy interfaces to evidence and study spatial heterogeneities, such as
molecular aggregates or interfacial concentration gradient at the origin of Marangoni stresses.
Light and Matter (ILM), and will also work in collaboration with the Liquid and Interface team.
He/she will also interact with other PhD students, post-doc and M2-students on close research
generation experiments. The funding is for two years for a junior post-doc (< 2 years after PhD).