Séminaires à venir / Upcoming

    • Optoacoustic phenotyping of cells and tissues: from cancer to metamaterials, par Thomas Dehoux (Institut Lumière Matière, Lyon)

      2020
      01
      28

      Despite deeper understanding of cancer metabolism, 90% of experimental drugs fail in clinical studies, mostly due to lack of efficacy. This stems from the lack of predictability of in vitro and in vivo models that are used to design generic drugs at preclinical stages, and from the limited histophysiological clues that can guide clinicians in adapting the generic therapy to each patient. At the same time, it is now well established that the mechanical properties of tumors control their physiology and phenotype. In this talk I will first present a novel quantitative, label-free microscopy technique based on Brillouin light scattering (BLS) to decipher the link between mechanical phenotype and drug efficacy.


      In the second part of this talk, I will discuss how the mechanical phenotype of tissues can be harnessed to engineer acoustic metamaterials. Biological composites have been known to possess remarkable mechanical performance that far exceed those of their constituents, due, in part, to their complex, hierarchal microstructure, composed of fibrous polymers, and other supra-molecular arrangements. While more is known about their mechanical properties in quasi-static settings, their phononic properties remain unexplored. In this study, we investigate the phononic behavior of micron-thick onion cells walls using laser generated, sub-GHz surface acoustic waves (SAWs). Our measurements reveal the presence of an acoustic band gap for SAWs, and suggest our biological material behaves as an organic, locally resonant metamaterial. Moreover, we show that this band gap can be phenotypically tuned, and anticipate these findings will yield new biologically-derived, "green", phononic materials.

    • Periodic boundary conditions in metamaterials: what they can't do, par Bart Van Damme (EMPA, Suisse)

      2020
      01
      29

      SEMINAIRE EXCEPTIONNELLEMENT UN MERCREDI à 11H

      The standard approach to evaluate the properties of periodic structures is the dispersion calculation by applying Bloch-Floquet boundary conditions on a unit cell. Exploiting the periodicity yields the prediction of the attenuation in bandgaps, and the wave speed of propagating waves. In this talk, I will exploit two examples where the Bloch-Floquet results are not sufficient to predict the dynamic response of simple, one-dimensional metamaterials.
      The first caveat of the resulting dispersion relation lies in its restriction to the first Brillouin zone. The real part of the wave number is a periodic function, which means that an infinite number of wave number solutions exists for each frequency. The energy distribution between the different wave modes for a given harmonic excitation depends on the size and boundary conditions of a sample. This has practical implications for e.g. wave steering and negative refraction. The second example shows how the introduction of aperiodicity in beams leads to classical effects such as band gaps and wave localization. Although some studies show that the properties of quasi- and aperiodic structures can be retrieved from periodic boundary conditions on a larger assembly of constitutive cells (the supercell approach), this cannot be generalized. In particular, samples that are too small to show any supercell should be modelled explicitly.

    • Séminaire IFSTTAR

      2020
      02
      11

      résumé à venir

    • titre à venir,par Sylvain Mézil (LIPhy)

      2020
      03
      10

      résumé à venir