Nicolas Bachelard, UC Berkeley

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Nicolas Bachelard, UC Berkeley, USA will give a seminar "Collective mechanisms for the self-organization of dynamic wave materials out of thermodynamic equilibrium" on Tuesday, March 20 at 11:00 a.m. in Room Pierre Cotton (groundfloor of ’Institut Fresnel).

Abstract :
The propagation of waves is typically shaped through a spatial modulation of the environment. For instance, in devices achieved by repeatedly stacking layers with different properties, the propagation of waves can be forbidden over continuous energy bandwidths, known as band-gaps. Such structures are routinely obtained either through top-down fabrication—such as e-beam lithography—or bottom-up processes—such as self-assembly. However, these conventional materials are static and arise in thermodynamic equilibrium, which results in inherently rigid structures, thus difficult to reconfigure and very sensitive to inhomogeneity and imperfections.

The observation of Nature teaches that complex materials and systems can be obtained through alternative mechanisms. Flocks of birds or schools of fish are examples of systems of high complexity that spontaneously self-organize, adapt to perturbations in their environment (e.g. predators), and collectively create coherent motions despite important heterogeneities in their populations.

In this talk, we use collective mechanisms to force the spontaneous organization of wave devices. We explain how an ensemble of dissimilar mobile particles can be driven to collectively form a coherent band-gap structure, which is able to self-heal or continuously adapt. Then, we demonstrate that similar mechanisms can be enforced to drive the emergence of coherent responses in solid-state platforms that are bestowed with resilience properties.

Contact : nicolas.bachelard chez gmail.com

Invitation : Marc Dubois, équipe CLARTE