IMX/IPHYS Talks - Unravelling the multiscale surface mechanics of soft solids

The mechanics of soft solid interfaces is key to the response of many natural and artificial systems at small scales. Yet, their underlying properties are vigorously debated, particularly for polymer networks. While molecular-scale theory predicts no interfacial changes with macroscopic deformation, multiple experiments suggest that interfacial tension increases with strain. In this presentation, I will detail two experimental systems that aim at settling this issue. This first one exploits the topography of rough surfaces under stretch, and the second focuses on the measurement of displacement fields near the interface of a deformed silicone gel. Their results demonstrate that the mechanical response of soft polymeric solids is intrinsically multi-scale, and that the interfacial elastic properties are modulated by the composition of the outer medium.

Bio: Nicolas Bain is a CNRS Researcher at the Institut Lumière Matière, in Lyon. After studying at the École Polytechnique, where he specialised in Mechanical Engineering, he went on to do a Master's degree in Civil and Environmental Engineering at MIT, and a PhD at the Physics Laboratory of the ENS in Lyon entitled ‘Hydrodynamics of polarized crowds, experiments and theory’. He then spent four years as a post-doctoral fellow in the Materials Science department at ETH Zürich, where he focused on the interfacial mechanics of polymer gels.

His research focuses on two themes, at the crossroads of physics and mechanics. Active matter, and the mechanics soft solids. In both areas, he has designed model experiments, developed advanced analysis tools, and used continuous theories to quantify fundamental behaviours that were previously inaccessible. Recently, he has been developing micromechanics experiments, which measure 3D deformations inside transparent polymer solids, with the aim of understanding the mechanical response of heterogeneous materials.