Matériaux, résonances et interfaces (MRI)

Responsable

Sébastien BIDAULT

Tél. : 01 80 96 30 49

Co-responsable

Valentina KRACHMALNICOFF

Tél. : 01 80 96 30 73

Membres permanents

Sébastien BIDAULT

Tél. : 01 80 96 30 49

Yannick DE WILDE

Tél. : 01 80 96 30 84

Samuel GRESILLON

Tél. : 01 80 96 30 37

Xiaoping JIA

Tél. : 01 80 96 30 43

Daniel KIEFER

Valentina KRACHMALNICOFF

Tél. : 01 80 96 30 73

Fabrice LEMOULT

Tél. : 01 80 96 30 50

Anne LOUCHET-CHAUVET

Tél. : 01 80 96 30 42

Sylvain MEZIL

Tél. : 01 80 94 30 94

Claire PRADA

Tél. : 01 80 96 30 53

Arnaud TOURIN

Tél. : 01 80 96 30 63

Actualités

Detection and characterization of targets in complex media using fingerprint matrices Le Ber, A., A. Goïcoechea, L. M. Rachbauer, W. Lambert, X. Jia, M. Fink, A. Tourin, S. Rotter, and A. Aubry Nature Physics 21, no. 10, 1609-1615 (2025) Résumé: When waves propagate through a complex medium, they undergo several scattering events. This phenomenon is detrimental to imaging, as it causes full blurring of the image. Here we describe a method for detecting, localizing and characterizing any scattering target embedded in a complex medium. We introduce a fingerprint operator that contains the specific signature of the target with respect to its environment. When applied to the recorded reflection matrix, it provides a likelihood index of the target state. This state can be the position of the target for localization purposes, its shape for characterization or any other parameter that influences its response. We demonstrate the versatility of our method by performing proof-of-concept ultrasound experiments on elastic spheres buried inside a strongly scattering granular suspension and on lesion markers, which are commonly used to monitor breast tumours, embedded in a foam mimicking soft tissue. Furthermore, we show how the fingerprint operator can be leveraged to characterize the complex medium itself by mapping the fibre architecture within muscle tissue. Our method is broadly applicable to different types of waves beyond ultrasound for which multi-element technology allows a reflection matrix to be measured.
Non-linear coupling in two non-linear delayed acoustic resonators Reda, J., M. Fink, and F. Lemoult Journal of the Acoustical Society of America 158, no. 3, 2130-2137 (2025) Résumé: Building on our previous work on a Hopf resonator that mimics the cochlear amplifier from Reda, Fink, and Lemoult [(2023). Europhys. Lett. 144(3), 37001], we now turn to the fact that the inner ear comprises thousands of such resonators, which interact through coupling mechanisms. To gain insight into these interactions, we investigate the coupling of two acoustic resonators with slightly detuned resonance frequencies, interacting through time-delayed feedback loops. By modulating the gain of the loop and the coupling strength, we demonstrate the emergence of frequency synchronization at low amplitudes and bifurcations leading to desynchronization at higher amplitudes. This tunable non-linear interaction offers insights into resonance phenomena in coupled systems, with potential implications for auditory modeling and complex acoustic systems.
Analog phase-sensitive time-reversal of optically carried radiofrequency signals Llauze, T., and A. Louchet-Chauvet Optics Letters 50, no. 16, 4874-4877 (2025) Résumé: Achieving low-latency time-reversal of broadband radiofrequency signals is crucial for reliable communications in dynamic, uncontrolled environments. However, existing approaches are either digitally assisted—making broadband extension challenging—or limited to amplitude modulation. In this work, we report the very first, to our knowledge, experimental realization of a fully analog, phase-preserving time-reversal architecture for optically carried radiofrequency signals. The method exploits the exceptional coherence properties of rare-earth ion-doped materials and leverages the well-established photon echo mechanism, widely used in quantum technologies. While our demonstration is conducted with a modest bandwidth, we identify the fundamental cause of this limitation and propose solutions for future scalability.
Exploring the limits to quantitative elastography: supersonic shear imaging in stretched soft strips Croquette, S., A. Delory, D. A. Kiefer, C. Prada, and F. Lemoult Physics in Medicine and Biology 70, no. 14 (2025) Résumé: Objective. Shear wave elastography has enriched ultrasound medical imaging with quantitative tissue stiffness measurements. We aim to explore the limitations that persist related to viscoelasticity, guiding geometry or static deformation. Approach. A nearly-incompressible soft elastomer strip is chosen to mimic the mechanical behaviour of an elongated tissue. A supersonic shear wave scanner measures the propagation of shear waves within the strip. It provides a wide range of shear wave velocities, from 2 to 6 m s<sup>−1</sup>, depending on the frequency, the static strain as well as the orientation of the strip. Main results. To explain these different measurements, the guided wave effect is highlighted and analysed from the dispersion diagrams provided by the spatio-temporal Fourier transform of the raw data. The guided waves are then described using a material model that accounts for both the rheology and the hyperelastic behaviour, and allows to extract the mechanical parameters of the sample. Significance. To overcome some limitations of current elastography, we propose a theoretical framework which allows the simultaneous characterization of the viscoelastic and hyperelastic properties of soft tissues, paving the way for robust quantitative elastography of elongated tissues.

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Nos activités portent à la fois sur l’étude et la caractérisation de matériaux en interaction avec des ondes électromagnétiques ou mécaniques, mais aussi sur la conception de matériaux artificiels (métamatériaux) avec une ingénierie précise de leurs propriétés optiques, microondes ou acoustiques. Nous exploitons et analysons des phénomènes de résonance et de guidage des ondes aux interfaces et leur incidence sur la propagation et les relations de dispersion spectrales et spatiales.
Ceci nous amène à la conception de nouveaux matériaux actifs, dépendant du temps ou biomimétiques, et aussi au développement de dispositifs expérimentaux d’imagerie, de spectroscopie et de métrologie. Nos efforts s’inscrivent dans des domaines tels que les technologies quantiques, la nanophotonique, la nanothermique, le contrôle non-destructif et la sismologie des milieux granulaires.

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Matériaux, résonances et interfaces (MRI)

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