Metamaterials and Phononics group

(left) Metasurfaces for the generation of vortices and acoustic holograms. (right) Acoustci pressure and sound absorption coefficient of a 13mm thick absorbing metasurface operating at 50 Hz.

Examples of acoustic holograms generated from predefined images by phase and amplitude modulation across a metasurface

Concept de Méta-égaliseur acoustique très large bande

Concept of very wide band acoustic meta-equalizer

Last publications

Scattering-free modulation of elastic shear-horizontal waves based on interface impedance theory
Mu Jiang, Yan-Feng Wang, Badreddine Assouar, Yue-Sheng Wang
Physical Review Applied, 2024, 20 (5), pp.054020. ⟨10.1103/PhysRevApplied.20.054020⟩
Multibranch Elastic Bound States in the Continuum
Shuowei An, Tuo Liu, Liyun Cao, Zhongming Gu, Haiyan Fan, Yi Zeng, Li Cheng, Jie Zhu, Badreddine Assouar
Physical Review Letters, 2024, 132 (18), pp.187202. ⟨10.1103/PhysRevLett.132.187202⟩
Isotacticity in chiral phononic crystals for low-frequency bandgap
Wei Ding, Tianning Chen, Dewen Yu, Chen Chen, Rui Zhang, Jian Zhu, Badreddine Assouar
International Journal of Mechanical Sciences, In press, 261, pp.108678. ⟨10.1016/j.ijmecsci.2023.108678⟩

Presentation

The Metamaterials and Phononics group (METAs) develops theoretical, numerical and experimental researches on acoustic and elastic metamaterials and metasurfaces, and more generally on wave propagation in complex media.

METAs research activities are based on 2 main axes:

• Understanding the physical mechanisms involved in metamaterials, metasurfaces and phononic crystals.

• The design and realization of innovative devices and systems capable of manipulating the propagation of acoustic and elastic waves in a highly controlled manner.

The approaches on which the strategy is based are theoretical, numerical and experimental.

The group has had long experience in the field of metamaterials, phononics and their interactions with acoustic, elastic and vibration waves. It has developed many innovative concepts, notably concerning :

      • acoustic absorption at very low frequencies
      • super-focusing
      • acoustic holography

With an intensive numerical calculation platform, fabrication equipment and experimental measurements for acoustics and vibrations, the METAs group tackle on the properties and functionalities of the metamaterials it develops. The group develops experimental approaches to measure the absorption, reflection and transmission of acoustic and elastic waves for the metastructures, and to qualify the performance of the associated devices.

Metamaterials, which are artificial structures with remarkable and unprecedented properties, allow to deal with new physics, to produce new functionalities, and to propose innovative systems and devices that may lead to scientific and technological breakthrough. To this end, the metamaterials group focuses on the development of applications for aeronautical, automotive, environmental, biomedical, and space fields. The group develops, for instance, metamaterials and metasurfaces for very low-frequency sound absorption, acoustic invisibility, illusion, biomedical imaging, holography, acoustic levitation, etc.

On another hand, the METAs group is developing several fruitful national and international collaborations, especially with universities in the USA (Georgia Institute of Technology), China (Tongji University, SCUT-Guangzhou and Tianjin University in particular) and South Korea (Seoul National University). These collaborations take various forms of exchanges and joint projects: PHC, PICS, etc.

Keywords

Metamaterials

Metasurfaces

Acoustics

Phononics

Vibrations

Waves in complex media

Topological and non-Hermitian metamaterials

Artificial Intelligence

Research topics

Metamaterials and acoustic metasurfaces

The group develops numerical models to understand the mechanisms of propagation and interaction of acoustic and elastic waves with complex metastructures. These models are based on classical approaches such as finite elements method, and on artificial intelligence algorithms such as deep-learning and convoluted neural network. In parallel, the group develops theoretical methods based on different formalisms to confront the numerical approaches to theory. Experimental fabrication and characterization of the different metastructures and devices are carried out, using the equipment available in the group.

Different applications are developed:

acoustic absorption in very low frequency regimes
energy harvesting
super-focusing
holography
Non-reciprocity

The group is also interested in the multifunctional aspect of its metastructures to integrate different functionalities in the same metamaterial or metasurface.

Projects:

US Air Force Office of Scientific Research, 2018 – 2022 (AIRCRAFT)
ICEEL Carnot, 2018-2021 (METACOM)
Région Grand Est; 2018 – 2021 (METACOUSTICS)

Theses:

Krupali Donda
Shiwang Fan

Articles:

Acoustic Metasurfaces, Nature Reviews Materials 3, (2018) 460., M. B. Assouar, B. Liang, Y. Wu, Y. Li, J-C. Cheng & Y. Jing
Acoustic metasurface-based perfect absorber with deep subwavelength thickness, Appl. Phys. Lett., 108 (2016) 063502. Y. Li & M. B. Assouar [Highlighted by AIP, Phys.org, ScienceDaily, etc. as most cited paper in 2016 and among most read in 2016 and 2017 and a ESI highly cited paper]

Topological and non-Hermitian metamaterials

The group develops topological metamaterials with propagating modes that are immune to defects (i.e. they are topologically protected). The protection associated with topological effects is strong. For example, waveguiding along interfaces allows the development of robust delay lines or waveguides, and more generally access to wave manipulation is much more efficient way than that offered by current acoustic devices.
Non-Hermitian metamaterials also derive from analogies between quantum mechanics and acoustics. Indeed, the concept of non-Hermiticity can be extended to acoustic structures by means of the spatial modulation of loss and gain within the metamaterial. The group is thus developing elastic and acoustic metamaterials, integrating constituents with balanced gain and loss. In this way, it obtains a multitude of phenomena, paving the way for unusual wave manipulations (PT-symmetry approach). Among others, metamaterials based on the PT-symmetry approach have been developed for applications concerning negative refraction or asymmetric propagation.

Project:

PHC France – Chine (2018-2019)

Thesis:

Sheng Wan (2016 – 2020)

Articles:

PT-Symmetry for Elastic Negative Refraction, Phys. Rev. Applied 10 (2018) 044071, Z. Hou, H. Ni & M. B. Assouar
Space-time phononic crystals with anomalous topological edge states, Physical Review Research 1 (3), 033069 (2019), M. Oudich, Y. Deng, M. Tao, Y. Jing
Ultrasonic nodal chains in topological granular metamaterials, Communications Physics 2 (2019) 154, A. Merkel & J. Christensen

Phononics and vibrations

The group is interested in the manipulation of elastic waves using phononic structures and elastic metamaterials for a wide range of applications. We investigate the dispersion of surface acoustic waves by metasurfaces made up of phononic pillars to give rise to confinement phenomena, Fano type resonance, and the acoustic analogue of electromagnetic induced transparency (EIT). The structure could be adapted to the design of platforms for the observation of quantum phenomena, opto-mechanical couplings or for the detection of biological species with very high sensitivity.
The group is also working on the development of metamaterials in the form of multifunctional plates offering the possibility of suppressing vibrations over a wide range of frequencies, and harvesting acoustic energy. The engineering of these artificial materials is specifically dedicated to aeronautic and aerospace applications. In addition, the team is developing work on phononic crystals and metasurfaces for vibration to deal with super-focusing phenomena for biomedical applications, asymmetric propagation or mechanical isolation at low frequencies.

Theses:

Liyun Cao (2016-2020)
Yi Zeng (2019-2023)
Simin Yuan (2017-2021)

Articles:

Elastic Metamaterial Insulator for Broadband Low-Frequency Flexural Vibration Shielding, Phys. Rev. Applied, 8 (2017) 054034. J-H. Oh, S. Qi, Y-Y. Kim & M. B. Assouar.
Rayleigh waves in phononic crystal made of multilayered pillars: confined modes, Fano resonances, and acoustically induced transparency, Physical Review Applied 9, 034013 (2018)., M. Oudich, B Djafari-Rouhani, B Bonello, Y Pennec, et. al.
Acoustic superfocusing by solid phononic crystals, Applied Physics Letters, 105 (2014) 233506. X. Zhou, M. B. Assouar & M. Oudich

Know-how

Numerical modelling and theoretical approaches

Development of numerical models (1D, 2D and 3D) based on finite elements, Plane Wave Expansion or FDTD
Development of artificial intelligence algorithms based on deep-learning and convoluted neural network
Development of theoretical approaches based on effective medium theory, lumped electrical models and multi-physics models

Manufacturing and measurements

Fabrication of metamaterials by additive manufacturing
Measurement and characterization of the acoustic and vibration wave field (1D, 2D and 3D). Reflection and transmission measurements
Scanning Doppler Laser Vibrometry (SLDV) for the frequency range from a few hundred Hz to 50kHz
Double acoustic impedance tube for transmission, reflection and absorption measurements
Elastic wave generation and measurement system for the ultrasonic range

Numerical calculation

3 numerical super-calculator stations (512 GB memory) equipped with finite element-based simulation software allow the modelling of all designs, particularly complex and 3D ones, of conceived metamaterials and metasurfaces