Waves In Metamaterials Research Articles

Novel metamaterial wave barrier structure with multiple frequency wide band gaps for rail transit vibration isolation

As a new kind of artificial composite material, locally resonant phononic crystal (LRPC) can attenuate and suppress the propagation of elastic waves in certain frequency range, which has a broad application prospect and value in the field of vibration and noise control. The traditional LRPC can only open one band gap (BG), but the vibration and noise in practical engineering are often multi-band, so the traditional LRPC cannot effectively cover the target frequency range, and the efficiency of vibration and noise reduction is greatly limited. In response to the shortcomings of traditional LRPC, this paper designs a novel locally resonant phononic crystal with multiple primitive cell combination structure (LRPCWMPCCS), which is a locally resonant supercell structure composed of five types of locally resonant single primitive cells. Firstly, the band structure of the LRPCWMPCCS is calculated using the finite element method, and compared with the band structure of traditional LRPC. Secondly, the frequency response function of the LRPCWMPCCS is calculated to evaluate its attenuation effect on elastic waves in the BG frequency range, and the generation mechanism of its locally resonant BG is explored by analyzing the displacement field and energy distribution characteristics at the BG edge. Then, the equivalent model of the LRPCWMPCCS is established for theoretical calculation of the BG range. Finally, the vibration isolation performance of LRPCWMPCCS wave barrier in practical engineering is analyzed, and the application prospects of the LRPCWMPCCS are discussed. The results show that the LRPCWMPCCS designed in this paper can open the multifrequency BGs, and the BGs width is wider. The number of BGs opened is positively correlated with the type of primitive cells inside the LRPCWMPCCS. Within the BG frequency range, the LRPCWMPCCS has a good attenuation effect on vibration waves, with attenuation values exceeding 20 dB. The spring-mass system equivalent model of the LRPCWMPCCS can accurately calculate its BG range and has good accuracy. The LRPCWMPCCS wave barrier has remarkable control and attenuation effect on vibration. Among them, the maximum vibration acceleration of traditional LRPC wave barrier and LRPCWMPCCS wave barrier is reduced by 18.51% and 39.50%, respectively. The relevant research results of this paper have great value and prospects in the design of LRPC with multifrequency and wide BGs, which can also provide a new method and idea for solving vibration and noise problems.

Elastic wave transport in angularly selective valley topological metamaterials plate

The valley degree of freedom has attracted increasing attention in elastic wave systems owing to its energy extrema at valleys and great potential in energy transportation. This study investigated the transport of valley edge states by angularly selective excitation in elastic wave metamaterials plate and designed a bifunctional elastic wave device in the bent waveguide containing two different interfaces. The supercell analysis revealed that the valley edge states exhibit symmetrical and anti-symmetrical distributions at two different interfaces. The straight and bent waveguides containing a single interface are designed, and the selective transport of valley edge states is observed due to the symmetrical or anti-symmetrical distributions at the interfaces. The angularly selective excitation of valley edge states by external excitation is demonstrated at the straight and bent interfaces. Based on these transport characteristics of valley edge states and the valley conservation mechanism, a bifunctional elastic wave device composed of a bent waveguide containing both two interfaces is designed. It can realize both the functions of the diode and the backward diode. The designed elastic wave device has the advantages of being a single structure with bifunctions. This study of topological valley transport with angularly selective characteristic may also have practical applications such as energy harvesting and sensing.

Arrest behavior of local resonators connected by nonlocal interaction in elastic wave metamaterials with machine learning prediction

In this study, the arrest behaviors of elastic wave metamaterials are analyzed in which the interconnected local resonators are considered. The influence of structural parameters on arrest performance is discussed to show good arrest properties. In order to support the theoretical calculation, both finite element simulation and fracture experiment are performed. Results show that additional energy barriers are generated in the higher subsonic range and the crack propagation resistance can be significantly improved by proper nonlocal interaction. Finally, based on the machine learning method, the energy release ratio G0/G of the elastic wave metamaterial is predicted. Comparing with the theoretical and predicted values, they are basically consistent in the stable range of energy release ratio.

Nonlinear soliton spiral induces coupled multimode dynamics in multi-stable dissipative metamaterials

With the robust and self-trapped properties, recent advances about soliton dynamics in multi-stable mechanical metamaterials have led to many innovative techniques from signal processing to robotics. This work proposes a multi-stable mechanical metamaterial driven by nonlinear dissipative solitons, in which the coupling and decoupling of multiple locomotion modes can be achieved. Based on a cylinder network with asymmetric energy landscape, the uniform field model of Landau theory is developed. During the theoretical calculation, the analytical solutions of several dissipative solitons are derived, which allow multiple special behaviors of solitary waves, such as wave velocity gaps, directional propagation and spiral phase transition. By incorporating such effects into robotic designs, a variety of complex movements can be achieved by a single structure, including hopping, rolling, rotating, swinging, bending and translational components. In particular, as excitation positions change, the mechanical metamaterial can flexibly switch multiple locomotion modes without changing configurations, e.g., spinning and spin-less, straight and oblique as well as coupled multimode movements. This work wishes to provide some new inspirations for the applications of nonlinear elastic wave metamaterials and phase transition theory in robotics.

Phonon Landau Quantization and Enhanced Lifetime in Deformed Graphene.

The pseudomagnetic field effect may offer unique opportunities for the emergence of intriguing phenomena. To date, investigations into pseudomagnetic field effects on phonons have been limited to sound waves in metamaterials. The revelation of this exotic effect on the atomic vibration of natural materials remains elusive. Our simulations of twisted graphene nanoribbons reveal well-defined Landau spectra and sublattice polarization of phonon states, mimicking the behavior of Dirac Fermions in magnetic fields. Both valley-specified helical edge currents and snake orbits are obtained. Analysis of dynamics indicates that phonon Landau states have extended lifetimes, which are crucial for the realization of Landau-level lasing. Our findings demonstrate the occurrence of the phonon pseudomagnetic field effect in natural materials, which has important implications for the mechanical tuning of phonon quantum states at the atomic scale.

Bright and dark optical solitons in optical metamaterials using a variety of distinct schemes for a generalized Schrodinger equation

Purpose The purpose of this study is to investigate the nonlinear Schrödinger equation (NLS) incorporating spatiotemporal dispersion and other dispersive effects. The goal is to derive various soliton solutions, including bright, dark, singular, periodic and exponential solitons, to enhance the understanding of soliton propagation dynamics in nonlinear metamaterials (MMs) and contribute new findings to the field of nonlinear optics. Design/methodology/approach The research uses a range of powerful mathematical approaches to solve the NLS. The proposed methodologies are applied systematically to derive a variety of optical soliton solutions, each demonstrating unique optical behaviors and characteristics. The approach ensures that both the theoretical framework and practical implications of the solutions are thoroughly explored. Findings The study successfully derives several types of soliton solutions using the aforementioned mathematical approaches. Key findings include bright optical envelope solitons, dark optical envelope solitons, periodic solutions, singular solutions and exponential solutions. These results offer new insights into the behavior of ultrashort solitons in nonlinear MMs, potentially aiding further research and applications in nonlinear wave studies. Originality/value This study makes an original contribution to nonlinear optics by deriving new soliton solutions for the NLS with spatiotemporal dispersion. The diversity of solutions, including bright, dark, periodic, singular and exponential solitons, adds substantial value to the existing body of knowledge. The use of distinct and reliable methodologies to obtain these solutions underscores the novelty and potential applications of the research in advancing optical technologies. The originality lies in the novel approaches used to obtain these diverse soliton solutions and their potential impact on the study and application of nonlinear waves in MMs.

Negative Refraction of Mixing Waves in Nonlinear Elastic Wave Metamaterials

Negative Refraction of Mixing Waves in Nonlinear Elastic Wave Metamaterials

Rapid validation of water wave metamaterials in a desktop-scale wave measurement system

Metamaterials have a unique ability to manipulate wave phenomena beyond their natural capabilities, and they have shown great promise in electromagnetic and acoustic wave control. However, their exploration in hydrodynamics remains limited. This article introduces a novel desktop-scale wave measurement system, specifically designed for the rapid prototyping and validation of water wave metamaterials. By utilizing 3D printing, the system accelerates the transition from theoretical designs to practical testing, offering a versatile and user-friendly platform. This is further enhanced by a synchronized stereo-camera setup and advanced data processing algorithms, enabling precise measurement and reconstruction of water wave behavior. Our experimental results demonstrate the system’s effectiveness in capturing intricate interactions between engineered structures and water waves. This significantly advances rapid prototyping for water wave metamaterial research, underscoring the system’s potential to catalyze further innovation in this emerging field.

Polarization-incident angle independent metamaterial wave absorber for enhanced electromagnetic energy harvesting in ultraviolet-B, visible spectrum, and near-infrared frequency range

A high-performance metamaterial wave absorber (MWA) in the ultraviolet-B, visible spectrum, and near-infrared frequency range for electromagnetic energy harvesting is presented. The elemental structure of the MWA is composed of twin ring resonators organized in a rotationally symmetrical configuration. This design's basic unit consists of three layers: the ground layer, featuring lossy gold properties; the intermediate layer, crafted from a lossy dielectric material that is silica; and the front layer, constructed using gold. The results indicate upon which an absorber can attain a comprehensive absorption. The outcomes that have been simulated using the Computer Simulation Technology (CST) Microwave Studio simulator show 313.19 THz, 525.55 THz, 576 THz, 766.71 THz, 847.2 THz, demonstrating absorption rates of 99.999%, 99.999%, 99.987%, 99.989%, and 99.999% for typically incident electromagnetic waves. The unit cell size is 560 × 560 nm²; this structure sets its sights on a captivating overall performance of the near-infrared, visible spectrum, and ultraviolet-B (UV-B) frequency bands. In addition, the energy harvester shows polarization independent at 0°, 45°, 90°, 135°, 180°, and 225° and wide-angle incident from 0° to 80° with good harvesting characteristics over the entire operating range. The surface current distribution is analyzed for insight into the energy harvesting mechanism. The present article introduces an alternative notion, expressed as a function of the phase velocities affecting various modes, throughout employing a limited periodic configuration. The impressive properties the indicated research shows are unity absorption, angle independency, etc. It is highly suitable for potential uses for energy harvesting in the near-infrared, visible spectrum, and (UV-B) frequency range with engineered dispersion characteristics.

Metamaterial Wave Absorber for Harvesting Electromagnetic Energy with Dispersion Characteristics Using Palm Oil Frond Graphitic Carbon

Metamaterial Wave Absorber for Harvesting Electromagnetic Energy with Dispersion Characteristics Using Palm Oil Frond Graphitic Carbon

Frequency-tunable quartic soliton in nonlinear negative-index metamaterials

An exact quartic soliton solution along with its constraint conditions in metamaterials (MMs) is presented on the basis of the nonlinear Schrödinger equation (NLSE) with second-, third- and fourth-order diffraction. Through analyzing the parameter relations based on the Drude model, it is demonstrated that the quartic soliton can only exist in the negative-index region (NIR) of self-focusing nonlinear MMs. With insight into the underlying parameter relations of quartic soliton, it is found that by selecting suitable frequency of incident wave, the quartic soliton in negative-index MMs (NIMs) exhibits frequency tunability or frequency stability. Particularly, the quartic solitons with different frequencies can propagate in an identical velocity, which provides a theoretical basis for realizing frequency division multiplexing (FDM) technology in nonlinear MMs. Different from pure-quartic soliton (PQS) in ordinary materials exhibiting oscillatory decaying tails in spatial domain and a flat top in frequency domain on logarithmic scale, the quartic soliton reported here possesses triangular distributions in both spatial and frequency domains. The presented results contribute to a fundamental theoretical support for future application of quartic soliton and are beneficial for exploring new solitary waves in MMs.

Hybrid rod-plate lattice metamaterial with broadband vibration attenuation

Based on the manufacturing advantages and design freedom of additive manufacturing, the control of elastic waves in metamaterials can be realized through the design of the unit cell. In this paper, a new design approach for 3D acoustic metamaterials consisting of rods and chiral plates (RCPM) was proposed, which displays omnidirectional low-frequency bandgaps over the irreducible Brillouin zone. The vibration modes at the boundary of the bandgaps were analyzed to illustrate the generation mechanism of the bandgaps. A spring-mass system and a clamped- clamped beam were developed to get the modes of the first bandgap boundaries. The influences of the main geometry parameters on the bandgaps were discussed systematically based on numerical simulation and theoretical formula, which demonstrates that the bandgap frequency range of the RCPM can be adjusted by altering the design. The elastic wave propagation in the metastructure was investigated by numerical and experimental approaches. The experimental results are in good agreement with the simulation, demonstrating bandgaps that occupy a much lower frequency range than what can be realized by Bragg scatter alone. The study provides a feasible approach to designing metamaterials for low-frequency vibration attenuation in engineering applications.

Covert Scattering Control in Metamaterials with Non-Locally Encoded Hidden Symmetry.

Symmetries and tunability are of fundamental importance in wave scattering control, but symmetries are often obvious upon visual inspection, which constitutes a significant vulnerability of metamaterial wave devices to reverse-engineering risks. Here, it is theoretically and experimentally shown that a symmetry in the reduced basis of the "primary meta-atoms" that are directly connected to the outside world is sufficient; meanwhile, a suitable topology of non-local interactions between them, mediated by the internal "secondary" meta-atoms, can hide the symmetry from sight in the canonical basis. Covert symmetry-based scattering control in a cable-network metamaterial featuring a hidden parity ( ) symmetry in combination with hidden- -symmetry-preserving and hidden- -symmetry-breaking tuning mechanisms is experimentally demonstrated. Physical-layer security in wired communications is achieved using the domain-wise hidden -symmetry as a shared secret between the sender and the legitimate receiver. Within the approximation of negligible absorption, the first tuning of a complex scattering metamaterial without mirror symmetry to feature exceptional points (EPs) of -symmetric reflectionless states, as well as quasi-bound states in the continuum, is reported. These results are reproduced in metamaterials involving non-reciprocal interactions between meta-atoms, including the first observation of reflectionless EPs in a non-reciprocalsystem.

Research progress on terahertz achromatic broadband polarization wave plates

The electromagnetic wave in the terahertz region shows many promising characteristics, such as non-ionization, “fingerprint” spectrum, sensitivity to weak resonance, strong penetration to non-polar substances, and so on. This study reviews the recent achievements of terahertz achromatic broadband polarization wave plates. The key parameters to evaluate the performance of terahertz polarized wave plates are described briefly. The relevant works, and benefits and drawbacks of terahertz wave plates based on diverse materials and designs, notably metamaterial wave plates, are summarized based on unique material attributes and design methodologies. Additionally, the current state of the terahertz achromatic broadband wave plate is generalized, along with the role of metamaterial in the design of terahertz wave plate, the innovative interdisciplinary path of terahertz metamaterial polarization is explained, and future research prospects are explored.

Dual-band topological states in actively convertible metamaterials with parallel platforms

Topological propagation in elastic wave metamaterials is widely investigated due to the superior transmission performance but most studies are focused on a single frequency range. This work proposes the elastic wave metamaterial composed of parallel platforms with active control, which illustrates topological interface states in two separate frequency ranges. In order to show basic features, band gap properties and localized modes in the rectilinear structure are considered at first. Then, the honeycomb system is investigated to present dynamic behaviors with two Dirac cones which belong to two frequency regions. The topological phase transition is identified by the eigenstates and topological invariants, respectively. Based on the k·p perturbation method, the effective Hamiltonian of two Dirac degeneracies is derived. Due to different stiffness of two platforms within a unit cell, two nontrivial degeneracies will be destroyed. Two band gaps support the interface states with topological protection and robust characteristic between lattices with different valley Hall phases. In addition, the topological transmission can be flexibly tuned by the active control system, which is supported by experiments. This work wishes to provide new designs of mechanical metamaterial with multiple functions.

2D-to-3D buckling transformability enabled reconfigurable metamaterials for tunable chirality and focusing effect

Recently, multifarious deformation approaches in nature have promoted dynamic manipulation for electromagnetic (EM) waves in metamaterials, and those representative strategies are mainly focused on the modulation of spectral parameters. Several works have also achieved tunable phase-gradient meta-devices. Here, to broaden the modulation freedom of mechanical deformation, we initially propose two reconfigurable metamaterials consisting of mirrored S-shaped meta-atoms selectively bonded on biaxially pre-stretched substrates. Planar meta-atoms with spin-insensitive transmittance are buckled into 3D morphologies to break residual symmetries by releasing the stress and to facilitate spin-dependent transmittance under circularly polarized incidence. Owing to the geometric anisotropy of S-shaped meta-atoms along the x and y axes, 3D chiral meta-atoms exhibit discriminate circularly cross-polarized transmittance under opposite spins. The underlying physical mechanism reveals that EM resonance originates from the excitation of electric dipoles and magnetic dipoles, and their cross coupling finally triggers the chiral effects of 3D meta-atoms. By introducing the gradient-phase design that keeps unchanged under various strains, two types of meta-atoms with specified orientations are interleaved to design a double-foci metalens, and its 2D-to-3D morphology transformation shortens the focusing length and facilitates the intensity change of two foci. Our approach in designing reconfigurable EM metamaterials with 2D-to-3D buckling transformability can be further extended toward terahertz even optical wavebands, and it may assist with deriving more applicable multi-functionalities in the aspects of imaging, sensing, and holograms.

Active control on topological interface states of elastic wave metamaterials with double coupled chains.

Topological elastic wave metamaterials have shown significant advantages in manipulating wave propagation and realizing localized modes. However, topological properties of most mechanical metamaterials are difficult to change because of structural limitations. This work proposes the elastic wave metamaterials with double coupled chains and active control, in which band inversion and topological interface modes can be achieved by flexibly tuning negative capacitance circuits. Finite element simulations and experiments are performed to demonstrate the topological interface modes, which show good agreements with the theoretical results. This research seeks to provide effective strategies for the design and application of topological elastic wave metamaterials.

Flower-shape resonator-based triple-band metamaterial wave absorbers to find the dispersion relation utilizing one dimensional (1-D) periodic waveguide

This paper proposes a flower-shape resonator-based triple band with a high-performance metamaterial wave absorber to find the dispersion relation utilizing one dimensional (1-D) periodic waveguide. The proposed absorber comprises flower-shaped square split ring resonator-based resonators separated by a Rogers RT5870 (lossy) dielectric layer with a thickness of 1.575 mm and back annealed copper with 0.035 mm thickness, and the size of the unit cell is 8 mm × 8 mm. The outcomes of simulations conducted using the Computer Simulator Technology (CST) Microwave Studio simulator reveal the presence of three absorption peaks at frequencies of 5.032, 7.96, and 13.94 GHz with an absorption of 99.709%, 99.966%, and 99.973%, respectively. As a result, this work presents a substitute concept in terms of phase velocity of mode in limited with periodic arrangements, showing it determines the type with terms of modalities a one-dimensional periodic concave parallel plates wavelength. The suggested phase velocity has been analysed using simulations using the CST Microwave Studio simulator and the CST eigenmode solver. A comparable circuit analysis demonstrates the superior performance of the metamaterial wave absorber, indicating its potential for excellent functionality within the advanced design system (ADS) software. Additionally, the proposed structures, modelled with the High-Frequency Structure Simulator (HFSS), exhibit a close correspondence with the maximum absorbance observed at each resonance peak in CST simulation results. The proposed research demonstrates excellent features such as unity absorption, angle insensitivity, and more, making it highly suitable for dispersion relation as well as C, X, and Ku band applications.

Orthotropic metamaterials with freely tailorable elastic constants

To control mechanical waves and structural vibrations, an important method is to design metamaterials with tailored elastic constants, but it is very difficult. In this paper, a simple and universal metamaterial design method is proposed. This orthotropic metamaterial is composed of elements arrayed periodically in space. The element includes two cuboid structures. The first structure is the basic structure of the element, and the second structure is the transformation of the first structure of the element. The first structure of the element is a cuboid structure composed of 24 bars connected by 8 nodes, and the second structure of the element is a cuboid structure composed of 36 bars connected by 14 nodes. This metamaterial has six independent elastic constants, so there is a large degree of freedom in the material design. Therefore, it has great application value in the fields of mechanical metamaterials, elastic wave metamaterials, acoustic metamaterials, and seismic metamaterials, and has also laid the foundation for realizing the dream of controlling mechanical waves and structural vibrations.

Design of an Ultra-Wideband Transparent Wave Absorber.

In this paper, a multilayer ultra-wideband transparent metamaterial wave absorber is proposed, which has the characteristics of ultra-wideband wave absorption, light transmission and flexible bending; in addition, due to the complete symmetry of the structure, the absorber has polarization insensitivity to incident electromagnetic waves. Both simulation and experimental results show that the frequency range of the microwave absorption rate is higher than 90% between 8.7 GHz and 38.9 GHz (between which most of the absorption rate can reach more than 95%), the total bandwidth is 30.2 GHz, and the relative bandwidth is 126.9%, realizing microwave broadband absorption and covering commonly used communication frequency bands such as X-band, Ku-band, and K-band. A sample was processed and tested. The test results are in good agreement with the results of the theoretical analysis, which proves the correctness of the theoretical analysis. In addition, through the selection and oxidation of indium tin (ITO) materials, the metamaterial also has the characteristics of optical transparency and flexibility, so it has potential application value in the window radar stealth and conformal radar stealth of weapons and equipment.