Missions

A soap film is a nanometrically thin water layer, covered by surface active molecules called surfactants (the soap molecules), sandwiched between two gas domains. If well designed, it can act as a liquid membrane, more or less permeable to the surrounding gas. Their main advantage is that they will never clog contrary to solid membranes. These properties are crucial to new energy-efficient chemical separation processes, currently corresponding to 10-15% of worldwide energy consumption. Separation devices have to be selective to one of the gas species, and this can be achieved in soap films thanks to the specific adsorption of gas species on the surfactant layer.
The objective of the postdoc is therefore to study this adsorption mechanism, for various gases. Two methods will be used. First, non-linear optics (Surface Harmonic Generation, fig. c) will be used to probe a single liquid-gas interface. This technique has the specificity to be highly surface-sensitive, and will allow us to probe gas adsorption and surfactant structure at the interface. Preliminary experiments have shown the SHG signal to be sensitive to the atmosphere composition. The SHG setup will be upgraded to allow for phase-resolved measurements to obtain more insight on the structure of the surfactant layer. Second, we will consider the case of a soap film with two interfaces. The postdoc will improve an existing Thin Film Pressure Balance and use it to explore how the interactions between the facing interfaces are modified by the gas atmosphere.

Activités

-setting up experiments
-collecting and analyzing experimental results
-presenting and writing publications

Compétences

PhD in physics or physico-chemistry, with a strong taste for experiments

Contexte de travail

The postdoc will work in the team Liquids and interfaces at Institute for Light and Matter (ILM) in Villeurbanne. ILM is a CNRS-Université LYon 1 research unit, located on Lyon Tech la Doua campus. With more than 300 employees, including a hundred doctoral students and post-docs, the iLM is a major player in physics and chemistry research in the Auvergne Rhône Alpes region, internationally recognized for the excellence of its research.