Thomas Brunet
thomas.brunet%40u-bordeaux.fr
Acoustic waves in Complex Media
Physics of waves in disordered media is a booming and fascinating research area. To investigate the richness and the complexity of exotic wave phenomena such as negative refraction or the Anderson localization, it is essential to have rationally designed “model systems”. For this purpose, we collaborate with the colleagues from physical chemistry laboratories of our campus (CRPP & LOF) who are able to produce various customized acoustic materials by using soft-matter techniques (emulsion-templating, microfluidics…). Therefore we have the opportunity to accurately study the transport of ultrasonic waves in heterogeneous media of many different types such as emulsions, suspensions, porous materials, etc.
Soft Acoustic Metamaterials
A promising way to get unusual acoustic properties such as a negative/zero acoustic index is to use 3D locally resonant metamaterials composed of sub-wavelength resonant particles exhibiting large mechanical contrasts with the surrounding medium. As an example, we reported the first ever 3D metafluid with a negative acoustic index by taking benefit from the strong low-frequency Mie-type resonances of porous microbeads with very low sound speeds randomly dispersed in aqueous yield-stress fluids. These resonant particles were made of soft porous silicone rubber or soft porous silica.
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Related publications:
- T. Brunet et al., Science 342 , 323 (2013)
- T. Brunet et al., Nat. Mater. 14 , 384 (2015)
- T. Brunet et al., EPJ Appl. Metamat. 2 , 3 (2015)
- S. Raffy et al., Adv. Mater. 28 , 1760 (2016)
- R. Poupart et al, RSC Advances. 10, (2020)
Soft gradient-index metasurfaces
As an alternative to 3D metamaterials, the recent emergence of metasurfaces has introduced new opportunities to realize wavefront shaping without restriction (e.g., directivity design, focusing, and singular field generation). We recently reported on a new class of acoustic gradient-index metasurfaces engineered from soft graded-porous silicone rubber with a high acoustic index for broadband ultrasonic 3D wavefront shaping in water. The functionalities of these soft flat lenses was illustrated through various experiments, which demonstrated beam steering and beam focusing as well as vortex beam generation.
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Related publications:
- A. Kovalenko et al., Soft Matter 12, 5154 (2016)
- A. Kovalenko et al., Soft Matter 13, 4526 (2017)
- A. Ba et al., Sci. Rep. 7, 40106 (2017)
- Y. Jin et al., Nat. Comm. 10, 143 (2019)
- R. Kumar et al., Journal of Porous Materials (2020)
Ultrasonic wave transport in resonant emulsions
The realization of highly monodisperse resonant systems, such as resonant emulsions, has allowed us to accurately describe all the key transport parameters of classical waves in disordered media. We recently reported on the impact of strong scattering resonances on ballistic and diffusive wave transport and we have also demonstrated the important influence of the relative refractive index of scattering inclusions on energy transport. As the next step, we aim at evidencing much more complex wave phenomena such as the Anderson localization that should occur in highly concentrated or highly resonating suspensions.
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Related publications:
- T. Brunet et al., Appl. Phys. Lett. 101, 011913 (2012)
- B. Mascaro et al., J. Acoust. Soc. Am. 133, 1996 (2013)
- T. Brunet et al., Phys. Rev. Lett. 111 , 264301 (2013)
- B. Tallon et al., Phys. Rev. Lett. 119, 164301 (2017)
- B. Tallon et al., Phys. Rev. B 101, 054202 (2020)