Watch: Apr.28 Prof. Dominique Langevin: Foams in Microgravity

Foams in Microgravity
Speaker: Dominique Langevin(Paris-Saclay University)
Apr.28, 2022
4pm GMT+8
Watch it on Bilibili
First image of foam in the SMD container, taken on March 9, 2020
 (liquid fraction 15%; window size 1.2 cm x1 cm)
Foams are dispersions of bubbles in liquids or solids and have many applications. It is therefore important to master the conditions in which they are stable. During their elaboration, the foams contain significant amounts of liquid, which flows quickly due to gravity. Experiments were planned in microgravity conditions to suppress drainage and to study the other foam destabilisation processes, ripening (growth of bubbles due to gas transfer between them) and coalescence (fusion of bubbles). The expectations were to stabilize foams with large liquid fractions f, which is impossible on Earth. Above a liquid fraction f ~ 36%, the bubbles disconnect. This is a jamming transition, which is found in other systems such as powders and grains or automobile traffic. The study of this transition in foams was another goal of the foam microgravity project.
Coalescence studies were performed in parabolic flights and in the International Space Station (ISS) in 2009 and 2012, they will be described. Coarsening is a much longer process and required the design of a suitable experiment container to be installed in the Fluid Science Laboratory of the ISS. A container called SMD (Soft Matter Dynamics) was constructed by Airbus. It includes light scattering and imaging diagnostics and it was installed in the ISS in 2018. The measurement capabilities of this container can be used to study different materials in exchangeable sample cell units, such as granular media, foams and emulsions. The container will be described.
Ripening experiments with foams in this container started in 2020. The SMD container includes a camera to measure bubble size distribution at the surface of the cell, and several multiple light scattering diagnostics to measure the bubble size in bulk as well as the foam dynamics, in particular inter-bubble rearrangements during ripening. The data are still under evaluation and preliminary results will be presented.
About the Speaker

DOMINIQUE LANGEVIN is CNRS research director. She first worked at the Physics Laboratory of Ecole Normale Superieure in Paris. She was afterwards director of the Paul Pascal Research Center, CNRS laboratory in Bordeaux. She currently works at the Laboratoire de Physique des Solides in Orsay. Her main research topic is the study of liquid interfaces in the presence of surfactants, polymers and/or nanoparticles, with a special focus on interfacial rheology. She is involved in an ESA project, scheduling experiments on aqueous foams in the ISS. She participated and still participates to a number of scientific committees and editorial boards; in the field of space sciences, she has been president of the physical science group of CNES and chair of the ESSC panel of physical and life sciences in space.


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