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8 novembre 2021: 1 événement

  • Séminaires Invités

    Lundi 8 novembre 11:00-12:30 - Eric Dufresne - Department of Materials, ETH Zürich

    Living Droplets Get To Work

    Résumé : Cells need to organize chemical reactions. In the classical view, lipid bilayer membranes define the boundaries of organelles – cellular sub-compartments with distinct chemical compositions. Recently, a number of liquid-like domains enriched in specific proteins and nucleic acids have been identified. While these membraneless organelles fulfill clear biochemical functions, they can potentially play mechanical roles.
    In this seminar, I will describe a series of experiments that span live cells, in vitro biochemical systems, and synthetic materials. Together, they demonstrate three distinct ways that membraneless organelles could perform mechanical work. In equilibrium, droplets’ interfacial energy drives adhesion and deformation. Near equilibrium, free energy liberated by condensation allows growing droplets to deform their surroundings. Far from equilibrium, chemical reactions localized to droplets can create chemical gradients that drive flow.
    We hope that these basic physical insights will help us to understand the physiology of cells and inspire new approaches to the design of synthetic materials.
    Contact : Elise Lorenceau

    En savoir plus : Séminaires Invités

8 novembre 2021: 1 événement

  • Soutenances de Thèse/HDR

    Lundi 8 novembre 14:00-17:30 -

    PhD. C. Arauz

    Résumé : Titre : Bubble growth in a confined polymer under temperature changes
    Résumé : We investigate the dissolution or growth of bubbles in polymeric systems driven by means of temperature variations. In this regard, laminated safety glass serves as an inspiration. The latter is a multi-layered assembly, which includes a thin, hygroscopic, polymeric film (typically, polyvinyl butyral-PVB) positioned in between two layers of glass. The assembly, guarantees that, if broken, sharp glass shards remain bonded to the polymeric interlayer. However, it is common to observe bubbles in laminated glass. These bubbles, which are anathema to the beautiful appearance of glass, can occur during production, quality testing at high temperatures or during normal operation and are typically associated with air oversaturation.
    During the thesis, an experimental transparent setup was developed to reproduce one of the main steps involved in the production of safety glass at the laboratory scale, i.e., autoclaving at high temperatures (140°C). The setup allows tracking the dissolution or growth of interfacial gases (gas pockets) or bubbles in glass/PVB/glass samples (or in otherwise transparent samples) when subjected to variations in temperature. We identify that air and water vapour follow distinct thermodynamic paths in terms of solubility with increasing temperature. As a result, water vapor leads to bubble growth while air favours dissolution. The observed kinetic behaviour of gas pockets/bubbles is highly non-monotonous and is strongly influenced by the rheology of the interlayer. A non-isothermal kinetic bubble model is thus proposed addressing the nature of the two gases, the finiteness of the system, as well as the complex viscoelastic behaviour of the polymeric interlayer that was characterized in depth.
    Jury :

    • Monsieur Matteo Ciccotti - Professeur ESPCI
    • Monsieur Christophe Raufaste - Maitre de conférence
    • Monsieur Rafael Estevez - Professeur des universités
    • Monsieur Christian Carrot - Professeur des universités
    • Monsieur Eric Dufresne - Professeur, ETH Zurich
    • Monsieur Constantin Coussios - Professeur Oxford University
    • Monsieur Keyvan Piroird - chef de plateforme R&D, Saint-Gobain Recherche

    En savoir plus : Soutenances de Thèse/HDR