Publications
296 results found
Lemkalli B, Kadic M, El Badri Y, et al., 2024, The emergence of low-frequency dual Fano resonances in chiral twisting metamaterials, Wave Motion, Vol: 127, ISSN: 0165-2125
We describe innovative designs of chiral mechanical metamaterials with a twist feature that induces Fano-resonances with a relatively high quality factor. Through a finite element analysis, we delineate the phononic dispersion curves and transmission responses provided by a syndiotactic symmetry configuration, which we contrast to the ones of homogeneous medium, isotactic nonchiral, and isotactic chiral beams. We demonstrate that the beam with the chiral syndiotactic cell based on the two octagonal plates exhibits dual Fano resonances at low frequencies. Finally, we explore the prospect of applying syndiotactic beam metamaterials as temperature sensors with significant sensitivity and quality factors for the proposed size at the vicinity of frequencies investigated. The dissipation effects influencing the acoustic wave attenuation in both solids and liquids, which may result in a decrease in the quality factors, are appropriately accounted for.
Touboul M, Lombard B, Assier RC, et al., 2024, High-order homogenization of the time-modulated wave equation: non-reciprocity for a single varying parameter, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 480, ISSN: 1364-5021
<jats:p>Laminated media with material properties modulated in space and time in the form of travelling waves have long been known to exhibit non-reciprocity. However, when using the method of low-frequency homogenization, it was so far only possible to obtain non-reciprocal effective media when both material properties are modulated in time, in the form of a Willis-coupling (or bi-anisotropy in electromagnetism) model. If only one of the two properties is modulated in time, while the other is kept constant, it was thought impossible for the method of homogenization to recover the expected non-reciprocity since this Willis-coupling coefficient then vanishes. Contrary to this belief, we show that effective media with a single time-modulated parameter are non-reciprocal, provided homogenization is pushed to the second order. This is illustrated by numerical experiments (dispersion diagrams and time-domain simulations) for a bilayered modulated medium.</jats:p>
Mangach H, Achaoui Y, Kadic M, et al., 2024, Polarization state conversion achieved by chiral mechanical metamaterial, New Journal of Physics, Vol: 26, ISSN: 1367-2630
Recently, metamaterials have driven advancements in wave propagation and polarization control. Chiral elastic metamaterials, in particular, have attracted considerable attention due to their distinctive properties, such as acoustical activity and auxeticity. Such characteristics arise from the additional degrees of freedom for tuning the embedded micro- and macro-rotations. In this study, we demonstrate an unusual energy exchange between longitudinal and in-plane shear waves in a 3D chiral mechanical metamaterial. The structural design is capable of inducing up to a 90∘ rotation in the plane of polarization. Additionally, this capacity for conversion is achieved by employing both an arrangement of chiral cells and a single meta-atom. This peculiar behavior enables a seamless switch between the three polarization states existing within a solid material, namely, the longitudinal state, the shear horizontal state, and the shear vertical state. Furthermore, a 2D discrete mono-atomic mass-spring model featuring inclined connectors is used to characterize the distinctive energy exchange between modes. This characterization is based on the retrieval of the pertinent elastic coefficients. The engineered chiral metamaterial polarization converter stands as a promising device for momentum conservation conversions and applications in elasto-dynamic polarimetry.
Lemkalli B, Guenneau S, Badri YE, et al., 2024, Seismic Waves Shielding Using Spherical Matryoshka-Like Metamaterials, Pages: 77-85, ISSN: 2367-3370
Among the most destructive natural mechanical events on the planet, seismic waves cause substantial damage and degradation to infrastructure throughout the world, posing a threat to humankind. The development of seismic metamaterials opens up a new frontier for shielding buildings and infrastructure against earthquakes. Furthermore, vibrations from seismic waves propagating at the surface of the earth are mostly due to Rayleigh waves, which have low frequencies, typically below 10 Hz. Within this critical range of frequencies, we report a novel architecture optimized for shielding against seismic waves, which is denoted as a spherical Matryoshka-like seismic metamaterial. We explore the response of this system using numerical analysis based on the finite element method. The band diagram in the irreducible Brillouin zone reveals, most notably, omnidirectional stop bands. Its frequency response analysis was carried out to better explore this metamaterial’s ability to attenuate seismic waves. The findings of this study open up new pathways for designing and optimizing seismic metamaterials. Thus, offering new avenues for improving earthquake shielding.
Ji Q, Zhang Q, Guenneau S, et al., 2024, Bilayer thermal metadevices that mold transient heat flows, International Journal of Heat and Mass Transfer, Vol: 218, ISSN: 0017-9310
Thermal manipulation has been widely researched due to its potential in novel functions, such as cloaking, illusion and sensing. To avoid the spatially inhomogeneous and anisotropic heat conductivity tensors (introduced by transformation thermodynamics), several thermal cloaks based on scattering cancellation (SC) approach are designed and experimentally demonstrated. However, the current SC cloak is only effective in the steady-state heat transfer condition as the heat capacity terms are neglected by the requirement of constant external fields. In order to expand the SC cloak to the transient regime, a bilayer scheme is introduced to achieve the accurate solutions of the camouflage equations considering time factors. Indeed, there are two equations to solve with two unknown quantities: first the thermal conductivity and second the product of specific heat capacity by the density. We construct thermal camouflage devices and verify their ability to mold dynamic heat flows both by simulations and experiments. Our proposed method paves an efficient avenue to extend SC approach to dynamic heat transfer regime.
Putley HJ, Guenneau S, Craster RV, et al., 2023, Effective properties of periodic plate-array metacylinders, Physical Review B, Vol: 108, ISSN: 2469-9950
We use semianalytic methods to model a periodic structure of plate-array cylinders (metacylinders), and derive several of the medium's effective material properties in the quasistatic limit. Subject to s-polarized [transverse-electric (TE)] light, the anisotropic dispersion of the crystal manifests as a Maxwell Garnett equation for the effective permittivity at leading order. This is performed both for the case of no material contrast between interior and exterior regions, and a nonunity normalized refractive index. In each case, the leading order effective permittivity is a function of the difference between Bloch wave and plate-array angles. As such, we envisage the metamaterial as being mechanically tunable through uniform mechanical rotation of the constituent metacylinders.
Chatzopoulos Z, Palermo A, Diatta A, et al., 2023, Cloaking Rayleigh waves via symmetrized elastic tensors, International Journal of Engineering Science, Vol: 191, ISSN: 0020-7225
In this work we propose a strategy based on coordinate transformation to cloak Rayleigh waves. Rayleigh waves are in-plane elastic waves which propagate along the free surface of semi-infinite media. They are governed by Navier equations that retain their form for an in-plane arbitrary coordinate transformation x=Ξ(X), upon choosing the specific kinematic relation U(Ξ(X))=u(x) between displacement fields in virtual, i.e. reference, (U) and transformed, i.e. cloaked, (u) domains. However, the elasticity tensor of the transformed domain is no longer fully symmetric, and thus, it is difficult to design with common materials. Motivated by this issue, we propose a symmetrization technique, based on the arithmetic mean, to obtain anisotropic, yet symmetric, elastic tensors for Rayleigh wave near-cloaking. In particular, by means of time-harmonic numerical simulations and dispersion analyses, we compare the efficiency of triangular and semi-circular cloaks designed with the original non-symmetric tensors and the related symmetrized versions. In addition, different coordinate transformations, e.g. linear, quadratic and cubic, are adopted for the semi-circular cloaks. Through the analyses, we show that a symmetrized semi-circular cloak, obtained upon the use of a quadratic transformation, performs better than the other investigated designs. Our study provides a step towards the design of feasible and efficient broadband elastic metamaterial cloaks for surface waves.
Lefebvre G, Dubois M, Achaoui Y, et al., 2023, Subwavelength pulse focusing and perfect absorption in the Maxwell fish-eye, Applied Physics Letters, Vol: 123, ISSN: 0003-6951
Maxwell's fish-eye is a paradigm for an absolute optical instrument with a refractive index deduced from the stereographic projection of a sphere on a plane. We investigate experimentally the dynamics of flexural waves in a thin plate with a thickness varying according to the Maxwell fish-eye index profile and a clamped boundary. We demonstrate subwavelength focusing and temporal pulse compression at the image point. This is achieved by introducing a sink emitting a cancelling signal optimally shaped using a time-reversal procedure. Perfect absorption and outward going wave cancellation at the focus point are demonstrated. The time evolution of the kinetic energy stored inside the cavity reveals that the sink absorbs energy out of the plate ten times faster than the natural decay rate.
Lemkalli B, Kadic M, El Badri Y, et al., 2023, Mapping of elastic properties of twisting metamaterials onto micropolar continuum using static calculations, International Journal of Mechanical Sciences, Vol: 254, ISSN: 0020-7403
Recent developments in the engineering of metamaterials have brought forth a myriad of mesmerizing mechanical properties that do not exist in ordinary solids. Among these, twisting metamaterials and acoustical chirality are sample-size dependent. The purpose of this work is, first, to examine the mechanical performance of a new twisting cubic metamaterial. Then, we perform a comparative investigation of its twisting behavior using the finite element method on microstructure elements computation, a phenomenological model, and we compare them to the Eringen micropolar continuum, for which we enunciate a straightforward approach for retrieving effective parameters using static computations. Notably, the results of the three models are in good qualitative and quantitative agreements. Finally, a systematic comparison of dispersion relations was made for the continuum and for the microstructures with different sizes in unit cells as final proof of perfect mapping.
Su Y, Li Y, Qi M, et al., 2023, Asymmetric Heat Transfer with Linear Conductive Metamaterials, PHYSICAL REVIEW APPLIED, Vol: 20, ISSN: 2331-7019
Craster R, Guenneau S, Kadic M, et al., 2023, Mechanical metamaterials, REPORTS ON PROGRESS IN PHYSICS, Vol: 86, ISSN: 0034-4885
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- Citations: 1
Vial B, Guenneau S, Hao Y, 2023, Topology optimization of a thermal cloak in the frequency domain, AIP ADVANCES, Vol: 13
Lenz SV, Guenneau S, Drinkwater BW, et al., 2023, Transformation twinning to create isospectral cavities, Physical Review B, Vol: 108, ISSN: 2469-9950
Bounded domains have discrete eigenfrequencies/spectra, and cavities with different boundaries and areas have different spectra. A general methodology for isospectral twinning, whereby the spectra of different cavities are made to coincide, is created by combining ideas from across physics including transformation optics, inverse problems, and metamaterial cloaking. We twin a hexagonal drum with a deformed hexagonal drum using a nonsingular coordinate transform that adjusts the deformed shape by mapping a near boundary domain to a zone of heterogeneous anisotropic medium. Splines define the mapping zone for twinning these two drums and we verify isospectrality by a finite-element analysis.
Wellander N, Guenneau S, Cherkaev E, 2023, Two-scale cut-and-projection convergence for quasiperiodic monotone operators, European Journal of Mechanics, A/Solids, Vol: 100, ISSN: 0997-7538
Averaging a certain class of quasiperiodic monotone operators can be simplified to the periodic homogenization setting by mapping the original quasiperiodic structure onto a periodic structure in a higher dimensional space using the cut-and projection method. We characterize the cut-and-projection convergence limit of the nonlinear monotone partial differential operator [Formula presented] for a bounded sequence uη in W01,p(Ω), where 1<p<∞, and Ω is a bounded open subset in Rn with Lipschitz boundary. We identify the homogenized problem with a local equation defined on a hyperplane, or a lower dimensional plane in the higher-dimensional space. A new corrector result is established.
Brun M, Guenneau S, 2023, Transformation design of in-plane elastic cylindrical cloaks, concentrators and lenses, WAVE MOTION, Vol: 119, ISSN: 0165-2125
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- Citations: 1
Chaumet PC, Guenneau SRL, 2023, Electromagnetic forces on a discrete concentrator under time-harmonic illumination, APPLIED PHYSICS LETTERS, Vol: 122, ISSN: 0003-6951
Chen Y, Wang K, Kadic M, et al., 2023, Phonon transmission through a nonlocal metamaterial slab, COMMUNICATIONS PHYSICS, Vol: 6, ISSN: 2399-3650
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- Citations: 3
Krushynska AO, Torrent D, Aragon AM, et al., 2023, Emerging topics in nanophononics and elastic, acoustic, and mechanical metamaterials: an overview, NANOPHOTONICS, Vol: 12, Pages: 659-686, ISSN: 2192-8606
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- Citations: 5
Tang K, Luz E, Amram D, et al., 2023, Dynamic cloaking of a diamond-shaped hole in elastic plate, APPLIED PHYSICS LETTERS, Vol: 122, ISSN: 0003-6951
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- Citations: 1
Brûlé S, Enoch S, Guenneau S, 2023, State of the art on the recovery of mechanical energy in the city: The role of seismic metamaterials, Pages: 523-524
Studies on structured soils, including seismic metamaterials, have shown the existence of complex wave phenomena within and around the structured zone. Seismic protection in conjunction with invisibility cloak has led to the emerging research area of seismic energy harvesting with seismic metamaterials. In this fast-developing niche, it is a question of evaluating the zones of energy concentration and deciding on the interest of valuing them by placing piezoelectric energy sensors. The article presents what is already being done and shows the interest of seismic metamaterials in this context.
Putley HJ, Guenneau S, Porter R, et al., 2022, A tunable electromagnetic metagrating, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 478, Pages: 1-22, ISSN: 1364-5021
We explore electromagnetic (EM) wave incidence upon gratings of reconfigurable metamaterial cylinders, which collectively act as a metagrating, to identify their potential as reconfigurable subwavelength surfaces. The metacylinders are created by a closely spaced, microstructured array of thin plates that, in the limit of small inter-plate spacing, are described by a semi-analytical continuum model. We build upon metacylinder analysis in water waves, translating this to EM for TE polarization (longitudinal magnetic field) for which the metacylinders exhibit anisotropic scattering; this is exploited for the multiple scattering of light by an infinite metagrating of uniform cylinder radius and angle, for which we retrieve the far-field reflection and transmission spectra for plane-wave incidence. These spectra reveal unusual effects including perfect reflection and a negative Goos–Hänchen shift in the transmitted field, as well as perfect symmetry in the far-field scattering coefficients. The metagrating also hosts Rayleigh–Bloch surface waves, whose dispersion is contingent on the uniform cylinder angle, shifting under rotation towards the light-line as the cylinder angle approaches the horizontal. For both plane-wave scattering and the calculation of the array-guided modes, the cylinder angle is the principal variable in determining the wave interaction, and the metagrating is tunable simply through rotation of the constituent metacylinders.
Cassier M, DeGiovanni T, Guenneau S, et al., 2022, Active exterior cloaking for the two-dimensional Helmholtz equation with complex wavenumbers and application to thermal cloaking., Philos Trans A Math Phys Eng Sci, Vol: 380
We design sources for the two-dimensional Helmholtz equation that can cloak an object by cancelling out the incident field in a region, without the sources completely surrounding the object to hide. As in previous work for real positive wavenumbers, the sources are also determined by the Green identities. The novelty is that we prove that the same approach works for complex wavenumbers which makes it applicable to a variety of media, including media with dispersion, loss and gain. Furthermore, by deriving bounds on Graf's addition formulas with complex arguments, we obtain new estimates that allow to quantify the quality of the cloaking effect. We illustrate our results by applying them to achieve active exterior cloaking for the heat equation. This article is part of the theme issue 'Wave generation and transmission in multi-scale complex media and structured metamaterials (part 2)'.
Ji Q, Chen X, Liang J, et al., 2022, Deep learning based design of thermal metadevices, International Journal of Heat and Mass Transfer, Vol: 196, ISSN: 0017-9310
Thermal metadevices obtained from transformation optics have recently attracted wide attention due to their vast potential for thermal management. However, these devices require extreme material parameters that are difficult to achieve in large-scale applications. Here, we design a thermal concentrator using a machine learning method and demonstrate the thermal concentration performance of the designed device. We first define an architecture with a single isotropic material. Deep learning models based on artificial neural networks are implemented to retrieve design geometry parameters ensuring that the required spatially varying anisotropy is achieved. We implement the optimized architecture into a thermal concentrator, fabricate samples and experimentally demonstrate that the designed metamaterial can simultaneously concentrate the heat flux in its core and minimize perturbations to the external thermal field. Our approach paves new avenues for the design of thermal management devices and, more generally, enables feasible solutions for inverse heat manipulation problems.
Farhat M, Guenneau S, Chen P-Y, et al., 2022, Scattering properties of acoustic beams off spinning objects: Induced radiation force and torque, APPLIED PHYSICS LETTERS, Vol: 121, ISSN: 0003-6951
Martí-Sabaté M, Guenneau S, Torrent D, 2022, High-quality resonances in quasi-periodic clusters of scatterers for flexural waves, AIP Advances, Vol: 12
Multiple scattering theory is applied to the study of clusters of point-like scatterers attached to a thin elastic plate and arranged in quasi-periodic distributions. Two types of structures are specifically considered: the twisted bilayer and the quasi-periodic line. The former consists in a couple of two-dimensional lattices rotated a relative angle, so that the cluster forms a moiré pattern. The latter can be seen as a periodic one-dimensional lattice where an incommensurate modulation is superimposed. Multiple scattering theory allows for the fast and efficient calculation of the resonant modes of these structures as well as for their quality factor, which is thoroughly analyzed in this work. The results show that quasi-periodic structures present a large density of states with high quality factors, being therefore a promising way for the design of high quality wave-localization devices.
Aznavourian R, Guenneau S, Ungureanu B, et al., 2022, Morphing for faster computations with finite difference time domain algorithms, EPJ Applied Metamaterials, Vol: 9, ISSN: 2272-2394
In the framework of wave propagation, finite difference time domain (FDTD) algorithms, yield high computational time. We propose to use morphing algorithms to deduce some approximate wave pictures of their interactions with fluid-solid structures of various shapes and different sizes deduced from FDTD computations of scattering by solids of three given shapes: triangular, circular and elliptic ones. The error in the L2 norm between the FDTD solution and approximate solution deduced via morphing from the source and destination images are typically less than 1% if control points are judiciously chosen. We thus propose to use a morphing algorithm to deduce approximate wave pictures: at intermediate time steps from the FDTD computation of wave pictures at a time step before and after this event, and at the same time step, but for an average frequency signal between FDTD computation of wave pictures with two different signal frequencies. We stress that our approach might greatly accelerate FDTD computations as discretizations in space and time are inherently linked via the Courant–Friedrichs–Lewy stability condition. Our approach requires some human intervention since the accuracy of morphing highly depends upon control points, but compared to the direct computational method our approach is much faster and requires fewer resources. We also compared our approach to some neural style transfer (NST) algorithm, which is an image transformation method based on a neural network. Our approach outperforms NST in terms of the L2 norm, Mean Structural SIMilarity, expected signal to error ratio.
Brûlé S, Enoch S, Guenneau S, 2022, Cloaking of bulk and surface mechanical waves, ISSN: 0277-786X
Ten years ago, two large scale experiments on seismic metamaterials demonstrated a cloaking effect for surface Rayleigh waves generated by a time-harmonic source at 50 Hertz in a sedimentary soil structured with boreholes 0.3m in diameter [1] and a lensing effect via negative refraction at 10 Hertz for surface Rayleigh waves generated by a multi-frequency source in a sedimentary soil structured with boreholes 2m in diameter [2]. These experiments have fueled the interest in large scale mechanical metamaterials for applications in civil engineering. Here, we propose that some experiments on broadband cloaking of spoof plasmon polaritons on metal surfaces structured with TiO2 [3] could be translated to the realm of seismic metamaterials. We point out that drawing analogies between surface Rayleigh waves in geophysics and spoof plasmon polariton in plasmonics, makes it possible to envision seismic cloaks and carpets at the decameter and kilometer scales. Research advances in photonics and plasmonics in the past twenty years might lead to a paradigm shift in earthquake engineering in the near future.
Chatzopoulos Z, Palermo A, Guenneau S, et al., 2022, Cloaking strategy for Love waves, Extreme Mechanics Letters, Vol: 50
Love waves are antiplane elastic waves which propagate along the surface of a heterogeneous medium. Under time-harmonic regime, they are governed by a scalar equation of the Helmholtz type. We exploit the invariance of this governing equation under an in-plane arbitrary coordinate transformation to design broadband cloaks for surface defects. In particular, we apply transformation elastodynamics to determine the anisotropic, position dependent, mechanical properties of ideal cloaks able to hide triangular and parabolic-shaped defects. Dispersion analysis and time-harmonic numerical simulations are employed to validate the proposed strategy. Next, we utilize layered monoclinic materials, with homogenized properties matching those of the ideal cloaks, to design feasible triangular-shaped cloaks. The performance of the layered cloaks is validated via parametric analysis of the dispersion curves, which converge to those of the ideal cloak when the unit cell-wavelength ratio vanishes. Finally, time-harmonic numerical simulations confirm a significant reduction of the defect-generated scattered fields by the layered cloaks.
Martí-Sabaté M, Guenneau S, Torrent D, 2022, High Quality Resonances in Quasi-Periodic Distributions of Scatterers, Pages: 579-580
We present a systematic study of the different modes that can present clusters of scatterers arranged in quasi-periodic distributions of scatterers. Although we focus our study in flexural waves, our approach can be applied to any kind of classical waves.
Meng Y, Hao Y, Guenneau S, et al., 2022, Metamaterial structures with Willis coupling for wave waves, Pages: 583-584
Willis coupling has been recently realized for acoustic waves and elastic flexural waves as the analogy of bianisotropy originally in electromagnetism. For further extension, we investigate its formulation in water waves and other kinds of elastic waves. Possible designs and numerical formulation in extracting the effective media with Willis coupling will also be discussed.
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