Applications Of Metamaterials Research Articles

Design of low-frequency and broadband acoustic metamaterials with I-shaped antichiral units

Controlling the propagation of low-frequency sound waves on the sub-wavelength scale is still a challenging problem. For the design of low frequency sound reduction materials, this paper introduces the I-shaped antichiral unit to the acoustic metamaterials with Mie resonance, which can manipulate the sub-wavelength acoustic waves and achieve effective low-frequency and broadband sound isolation. By adjusting the width of the ligament, the proportion of the omnidirectional bandgap is 65.6 % in the subwavelength range. Firstly, the designed acoustic metamaterials are constructed by rotating the I-shaped units with mutually orthogonal periodic distribution. The parametric geometric model of metamaterials is established, and the low-frequency and wide bandgap can be effectively realized by adjusting the ligament width. Then, the investigation of sound pressure and phase reveals that the bandgaps attribute to the Mie resonant mode. Furthermore, based on the transfer matrix method, the effective bulk modulus and effective mass density of acoustic metamaterials are derived. The results show that the frequency range of the negative effective parameters obtained is consistent with that of the band gap. Finally, experimental tests are carried out, the region where attenuation occurs is in good agreement with the bandgap range (1158–2500 Hz) predicted by eigenfrequency analysis. The experimental tests verify the effectiveness of the designed antichiral acoustic metamaterials for low frequency sound reduction. The introduction of the antichiral unit provides a broad space for the application of acoustic metamaterials in low-frequency sound reduction.The low-frequency and broadband can be effectively realized by adjusting the ligament width.The low-frequency can be effectively realized by adjusting the ligament width.The experimental tests verify the effectiveness of the designed antichiral unit.

A Review of Recent Research into the Causes and Control of Noise during High-Speed Train Movement

Since the invention of the train, the problem of train noise has been a constraint on the development of trains. With increases in train speed, the main noise from high-speed trains has changed from rolling noise to aerodynamic noise, and the noise level and noise frequency range have also changed significantly. This paper provides a comprehensive overview of recent advances in the development of high-speed train noise. Firstly, the train noise composition is summarized; next, the main research methods for train noise, which include real high-speed train noise tests, wind tunnel tests, and numerical simulations, are reviewed and discussed. We also discuss the current methods of noise reduction for trains and summarize the progress in current research and the limitations of train body panels and railroad sound barrier technology. Finally, the article introduces the development and potential future applications of acoustic metamaterials and proposes application scenarios of acoustic metamaterials for the specific needs of railroad sound barriers and train car bodies. This synopsis provides a useful platform for researchers and engineers to cope with problems of future high-speed rail noise in the future.

Metamaterials: From fundamental physics to intelligent design

AbstractMetamaterials are artificial structures with the ability to efficiently control light‐field, attracting intensive attention in the past few decades. People have studied the working principles, design strategies, and fabrication methods of metamaterials, making this field cross and combine with many disciplines, including physics, material science, electronics, and chemistry. In recent years, with the rapid development of high‐efficiency and multifunctional metasurfaces, which are a two‐dimensional version of metamaterials, great efforts have been made to push this material to practical applications. In particular, the introduction of artificial intelligent (AI) algorithms enables metamaterials‐based photonic devices that exhibit excellent performances and intelligent functionalities. In this review, we first introduce the basic concepts, working principles, design methods, and applications of metamaterials, and then focus on the rapidly developing metamaterials research combined with AI algorithms. Finally, we conclude this review with personal perspectives on the current problems and future directions of metamaterials research and developments.

Hot Electron Extraction Enabled By Single-Crystal Metal Films and Nanostructures

In contrast to conventional photovoltaic devices which rely on bulk semiconductor material absorption and separation of electron-hole pairs, surface plasmon-based solar energy harvesting employs rectifying metal/dielectric interfaces to capture light and separate charges. Here, we describe the requirements for efficient hot electron extraction in plasmonic photovoltaic devices and demonstrate a new scalable and environmentally friendly electroless deposition method for single-crystal epitaxial noble metals films and nanostructures. The method produces ultra-smooth, low loss, single-crystal noble metal films ideal for subtractive patterning of nanostructures through ion beam milling, and high definition, sub-wavelength single crystal nanostructures through lithographic patterning methods. We describe the nucleation and growth of these metal films and nanostructures in the absence and presence of anionic shape-control agents and examine the role of specific anions in determining the resulting film and nanostructure morphologies via scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). These effects have been exploited to yield large area patterned, and shape-controlled nanoarrays of single crystal metal nanostructures for plasmonic and metamaterial applications. These approaches offer new and cost effective routes to achieve crystalline, shape-controlled surface nanostructure to enable efficient hot electron extraction for energy harvesting and catalysis applications and new noble metal alloys for improved electrocatalysis.

Metamaterial Devices from Microwaves and Terahertz to Optical Frequencies

Microwave to optical frequency was used to review metamaterial applications. The regions are divided into hard and soft. Constructed devices, such as sources, lenses, switches, modulators and detectors, operate within these components. Programmable metamaterials can realise several distinct functionalities using a field-programmable gate array. For example, a cloak was constructed using artificially structured metamaterials under a band of microwave frequency.

A nonlinear metamaterial plate for suppressing vibration and sound radiation

Nonlinear acoustic metamaterials (NAMs) exhibit extraordinary properties for low-frequency and broadband vibration mitigation. Despite the increasing attention received, exotic properties and the physical mechanisms underpinning NAM-enabled functionalities have not been fully understood. Moreover, investigations on the sound radiation of NAM structures have not been reported. Here we systematically investigate the vibration of a NAM plate and its sound radiation using experimental and theoretical methods. We experimentally demonstrate that the NAM plate can entail significant vibration and sound radiation reduction in an ultra- low and broad frequency band, typically from 20 to 1800 Hz, without any artificial damping element. This is attributed to the nonlinear coupling among multiple local resonances, and the nonlinear collision-friction damping. This understanding allows the proposal of two design strategies to achieve ultra- low and broadband vibration and sound radiation suppression with NAMs. Moreover, we clarify the mechanisms governing the ultra- low and broadband features, including bandgaps, output saturation of nonlinear resonances, efficient energy pumping due to high-order harmonics and chaos, and modulation of nonlinear resonance modal amplitudes and shapes. These mechanisms and diverse wave behaviors are inter-related and occur concurrently. The reported study provides answers to several key questions of paramount importance in designs, mechanics and applications of nonlinear metamaterials.

In-plane elasticity of a novel arcwall-based double-arrowed auxetic honeycomb design: Energy-based theoretical analysis and simulation

In this paper, a new design of auxetic honeycomb is proposed for mechanical performance enhancement by combining the arc-shaped wall and the normal double-arrowed auxetic configuration. On basis of Mohr's 2nd theorem and Castigliano 2nd theorem, an analytical model considering strut bending and stretching is developed to modulate the in-plane mechanical properties of the proposed honeycomb with the geometric parameters. Further, an integrated experimental, simulation and theoretical approach is carried out to investigate its elastic properties and Poisson's ratios in a wide range. The comparison shows that the theoretical results are in good agreement with the experimental and simulation results, verifying the established analytical model. The results reveal that both the in-plane modulus and the Poisson's ratio of the proposed auxetic honeycomb are simultaneously improved compared to the typical double-arrowed and the re-entrant hexagonal designs, and show high and diverse dependencies on the geometric parameters. Additionally, the honeycomb features a stiffer modulus and stronger auxeticity along y direction than that along x direction when the arc angle of “bone”, θ1, not exceeding a “turning point”. The present design may provide an extensive reference for the design and application of mechanical meta-materials.

Dynamic and Active THz Graphene Metamaterial Devices.

In recent years, terahertz waves have attracted significant attention for their promising applications. Due to a broadband optical response, an ultra-fast relaxation time, a high nonlinear coefficient of graphene, and the flexible and controllable physical characteristics of its meta-structure, graphene metamaterial has been widely explored in interdisciplinary frontier research, especially in the technologically important terahertz (THz) frequency range. Here, graphene’s linear and nonlinear properties and typical applications of graphene metamaterial are reviewed. Specifically, the discussion focuses on applications in optically and electrically actuated terahertz amplitude, phase, and harmonic generation. The review concludes with a brief examination of potential prospects and trends in graphene metamaterial.

Broadband low-frequency sound attenuation in duct with embedded periodic sonic black holes

This paper studies the sound wave propagation and attenuation characteristics in a new type of acoustic device, which is constructed by periodically embedding sonic black holes (SBHs) into an air-filled waveguide. The SBH is realized by cascading a set of rigid rings with linearly or quadratically changing inner radii into each unit cell section. Acoustic impedance variation rendered by this specially tailored profile progressively slows down the incident sound velocity to generate the SBH effects including wavelength compression, energy focalization, and dissipation with inherent damping in the duct. Upon developing and validating a model based on the transfer matrix method (TMM), the sound transmission loss (STL) of a finite-length periodic duct with different geometrical parameters is investigated. Different from a single SBH unit which can trigger the complete SBH process only above the cut-on frequency, the proposed periodic arrangement offers strong attenuation bands in the low-frequency range of the STL curve well below the frequency barrier imposed by the cut-on frequency of a single SBH unit. Mechanism studies reveal that these attenuation bands result from the interplay between the Bragg scattering and the SBH-specific slow-sound effects. The latter is shown to equivalently increase the effective lattice constant of the periodic duct, thus lowering the frequency of the Bragg bandgap. It is also shown that in contrast to conventional locally-resonant metamaterials, the proposed device exhibits far less dependence on the number of unit cells and the amount of rigid rings to activate a significant low-frequency stop-band. These appealing features could greatly simplify the design and application of SBH-based metamaterials, making it a promising solution for low-frequency wave manipulation and noise control.

Examining the impact of asymmetry in lattice-based mechanical metamaterials

Lattice-based mechanical metamaterials can be tailored for a wide variety of applications by modifying the underlying mesostructure. However, most existing lattice patterns take symmetry as a starting point. We show that asymmetric lattice patterns can be more likely to have certain mechanical properties than symmetric lattice patterns. To directly compare the effects of asymmetric versus symmetric lattice arrangements, a constrained design space is defined. A generative design process is used to generate both symmetric and asymmetric lattice patterns within the design space. Asymmetric lattice patterns are shown to have distinct metamaterial property spaces from symmetric lattice patterns. Key design features are identified that are present predominantly in asymmetric lattice patterns. We show that asymmetric lattice patterns with two of these features (arrows and spider nodes) are more likely to induce a broader range of Poisson’s ratios and larger shear stiffness values, respectively, compared to lattice patterns without these features. In addition, we show that symmetry can play a role in hampering the impact of multiple features when present. This work provides insights into the benefits of using asymmetric lattice patterns in select metamaterial design applications.

Applications of Nanoporous and Metamaterials: An Unornamented Review

Applications of Nanoporous and Metamaterials: An Unornamented Review

Fabrication and characterization of shape memory auxetic metamaterial

The process of repeating shape memory cycle of the shape memory foam whose initial structure is nonauxetic is more complex. In this cases, only one-shot deformation, which will greatly limit the application of this smart metamaterial. Thus, in this study, we report a feasible approach of fabricating the original structure of shape memory foams with auxetic property based on second curing method. The commercial soft polyurethane foam material and shape memory epoxy resin was used in fabricating the shape memory auxetic foam. Polyurethane component plays role in the similar function of “auxetic mold,” while shape memory polymer act as fixing auxetic structure of foam. The negative Poisson’s ratio was achieved around −0.22. Tunable foam mechanical property was demonstrated by structural control according to its shape memory property. The functional filler was employed to realize the wireless actuation of auxetic foam. The excellent shape memory properties have been achieved as well. The combination of smart materials and metamaterial structure makes it have excellent structural mechanical properties and intelligent properties of materials, which greatly expands their potential application prospects.

Terahertz waves dynamic diffusion in 3D printed structures

Applications of metamaterials in the realization of efficient devices in the terahertz band have recently been considered to achieve wave deflection, focusing, amplitude manipulation and dynamical modulation. Terahertz metamaterials offer practical advantages since their structures have typical sizes of hundreds microns and are within the reach of current three-dimensional (3D) printing technologies. Here, we propose terahertz photonic structures composed of dielectric rods layers made of acrylonitrile styrene acrylate realized by low-cost, rapid, and versatile fused deposition modeling 3D-printing. Terahertz time-domain spectroscopy is employed for the experimental study of their spectral and dynamic response. Measured spectra are interpreted by using simulations performed by an analytical exact solution of the Maxwell equations for a general incidence geometry, by a field expansion as a sum over reciprocal lattice vectors. Results show that the structures possess specific spectral forbidden bands of the incident THz radiation depending on their optical and geometrical parameters. We also find evidence of disorder in the 3D printed structure resulting in the closure of the forbidden bands at frequencies above 0.3 THz. The size disorder of the structures is quantified by studying the dynamics diffusion of THz pulses as a function of the numbers of layers of dielectric rods. Comparison with simulations of light diffusion in photonic crystals with increasing disorder allows estimating the size distributions of elements. By using a Mean Squared Displacement model, from the broadening of the pulses’ widths it is also possible to estimate the diffusion coefficient of the terahertz radiation in the photonic structures.

Topology optimization of anisotropy hierarchical honeycomb acoustic metamaterials for extreme multi-broad band gaps

Acoustic metamaterials (AMMs), especially based on hierarchical honeycomb structure and topology-optimized design with suitable mechanical properties and low-frequency band gaps (BGs), have been studied recently. The present work reports a series of anisotropy hierarchical honeycomb structure lattices composed of the cell walls and vertices of regular hexagonal lattice replacement honeycombs of various sizes, as well as improved BG evaluation indicators. The band structures of three different types of unfilled hierarchical honeycomb lattices are calculated and the mechanism of BGs generation is analyzed. To obtain multi-broad BGs in the low-frequency range, the scatterers filling schemes are optimized by using a genetic algorithm (GA). Additionally, the effects of structural/material parameters on the BG characteristics of the optimized structures are discussed. Finally, the transmission loss (TL) experiment verified the optimization of the structures. This paper aims to promote the application of hierarchical honeycomb metamaterials with low-frequency vibration isolation in the industrial field.

Metamaterial electromagnetic wave absorbers and devices: Design and 3D microarchitecture

• In this review, the design principles of the new MMAs: bionic design and new artificial design, are explored. • Bionic design mainly includes the design of imitating the microstructures of moth-eye and diatom frustum. • 3D printing technology make MMAs light and more complex. Metamaterials refer to a class of artificial composite structures with supernormal physical properties that natural materials do not have. The emergence of metamaterials has opened up new research directions for classical electromagnetic theory and made it possible to manipulate electromagnetic waves effectively. One of most important applications of metamaterials is metamaterial absorbers (MMAs). The properties of MMAs depend on the material composition, cell size and structure, which could often achieve "perfect" absorption through reasonable design. This review starts with the development of MMAs and describes the status of this absorber, then mainly focuses on bionic design and new artificial design. Specifically, it is to draw inspiration from natural plants and animals, design novel structures to get better absorbing properties. Furthermore, the artificial design can achieve the optimize absorption capacity as well as absorption bandwidth. What's more, this review summarizes the 3D printing technology to prepare MMAs that are different from traditional printed circuit board technology. The MMAs produced by 3D printing technology can prepare more complex shapes, and has light weight and better absorbing properties. This review mainly reports the design (bionic and artificial) and preparation (3D printing technology) of metamaterial absorbers (MMAs) with super-absorbent capacity. Specifically, this review is to draw inspiration from natural plants and animals, design structures with the capacity to manipulate electromagnetic waves absorption, and use artificial patterning methods to optimize absorption capacity as well as absorption bandwidth.

Structural, dielectric, and magnetic properties characterization of sol–gel synthesized CaxZn(0.90-x)Ni0.10Fe2O4 nanopowder and its application as flexible microwave substrate with polarization-insensitive SNG metamaterial

In this work, CaxZn(0.90-x)Ni0.10Fe2O4 nanopowder-based new flexible microwave substrates are prepared using the sol–gel method for metamaterial applications. Three different x values are chosen as x = 25, 50, 75 and termed as Ca25, Ca50, and Ca75 respectively. The structural and morphology of synthesized materials are investigated with XRD and FESEM analysis. The dielectric properties were also determined and the obtained values for dielectric constant (εr) and loss tangents (Tδ) are ranges from 3.25 to 4.25 for εr and 0.0025 to 0.0065 for Tδ for Ca25, Ca50, and Ca75 respectively. In addition, the magnetic permeability μr and magnetic loss tangent (Tδm) values are estimated from the scattering parameters S11 and S21 obtained by using Agilent module 85071E, and the achieved values of μr and Tδm are ranges from 0.875 to 1.00 and 0.0035 to 0.0075 respectively. Later, the proposed metamaterial unit cell consists of a square split ring resonator (SSRR) and a circular SRR (CSRR) loaded with a plus shape is designed and fabricated on the proposed flexible substrates obtained from the synthesized CaxZn(0.90-x)Ni0.10Fe2O4 nanopowders to validate their application as metamaterials. The novelty of the proposed work is found in the unit cell being polarization-insensitive and having a multiband, low electrical dimension that improves the EMR, single-negative characteristics with high flexibility and lightweight and suitable for C, X, and Ku bands of microwave regime.

Laminated plate-type acoustic metamaterials with Willis coupling effects for broadband low-frequency sound insulation

Acoustic metamaterials provide a powerful tool for designing effective noise-reducing means at subwavelength scales. This paper is concerned with the sound insulation characteristics of plate-type acoustic metamaterials under some pragmatic conditions, including the effect of structure scale on the sound insulation performance, the Willis coupling effect in multilayer plate-type acoustic metamaterials, and the acoustic coupling between plate-type acoustic metamaterials and existing structures. Herein, laminated plate-type acoustic metamaterials (LPAM) composed of multilayer plate-type acoustic metamaterials sandwiched with porous materials are constructed to effectively insulate broadband low-frequency noise. By a numerical study on the normal, oblique, and diffuse-field incident sound transmission loss (STL) of the proposed LPAM and its constituent layers, the presence of superior sound insulation performance and the governing physical mechanism are discussed. The effectiveness of numerical study is validated by the STL experiments performed in a sound impedance tube for small-scale samples and in a reverberation and anechoic chamber for large-scale samples. The proposed LPAM construction, analysis technique, and reported findings may contribute to the design and application of plate-type acoustic metamaterials for broadband low-frequency noise control.

Double-Lattice Packing of Pentagonal Gold Bipyramids in Supercrystals with Triclinic Symmetry.

Pentagonal packing is a long-standing issue and a rich mathematical topic, brought to the fore by recent progress in nanoparticle design. Gold pentagonal bipyramids combine fivefold symmetry and anisotropy and their section varies along the length. In this work, colloidal supercrystals of pentagonal gold bipyramids are obtained in a compact arrangement that generalizes the optimal packing of regular pentagons in the plane. Multimodal investigations reveal a two-particle unit cell with triclinic symmetry, a lower symmetry than that of the building blocks. Monte Carlo computer simulations show that this lattice achieves the densest possible packing. Going beyond pentagons, further simulations show an odd-even effect of the number of sides on the packing: odd-sided bipyramids are non-centrosymmetric and require the double-lattice arrangement to recover inversion symmetry. The supercrystals display a facet-dependent optical response that is promising for sensing, metamaterials applications, and for fundamental studies of self-assembly processes.

A novel workflow to fabricate a patient-specific 3D printed accommodative foot orthosis with personalized latticed metamaterial

Patients with diabetes mellitus are at elevated risk for secondary complications that result in lower extremity amputations. Standard of care to prevent these complications involves prescribing custom accommodative insoles that use inefficient and outdated fabrication processes including milling and hand carving. A new thrust of custom 3D printed insoles has shown promise in producing corrective insoles but has not explored accommodative diabetic insoles. Our novel contribution is a metamaterial design application that allows the insole stiffness to vary regionally following patient-specific plantar pressure measurements. We presented a novel workflow to fabricate custom 3D printed elastomeric insoles, a testing method to evaluate the durability, shear stiffness, and compressive stiffness of insole material samples, and a case study to demonstrate how the novel 3D printed insoles performed clinically. Our 3D printed insoles results showed a matched or improved durability, a reduced shear stiffness, and a reduction in plantar pressure in clinical case study compared to standard of care insoles.

Impact of the Scatterer Type on Ultrasound Wave Propagation in Microstructure Composites: Calculation and Application

This study is motivated to quantitatively analyze the differences among various multiple scattering models to determine the role played by the scatterer type in ultrasonic wave propagation. By calculating the transmission and reflection coefficients of the composites, the results of multiple scattering theoretical models of different scatterer types have been evaluated. The problem of acoustic properties in a fluid matrix containing different types of micron-scale scatterers operating in the ultrasound frequency range is considered. Theoretical calculations are conducted for composites with different mechanical properties. Meanwhile, the theoretical results have been compared with numerical finite element method simulations, which can be regarded as a benchmark to verify the validity of different theoretical models. The results show that the composites can achieve negative acoustic properties by selecting appropriate resonant scatterers, paving the way for searching ultrasonic metamaterials with desired negative acoustic properties. We further explored the application of microstructure ultrasonic metamaterials by enhancing the ultrasound transmitted energy through the high-impendence skull layer, having the potential for non-invasive ultrasound brain imaging and therapy.