Design Of Metamaterials Research Articles

Lightweight composite from graphene-coated hollow glass microspheres for microwave absorption

In developing the effective and lightweight materials for microwave absorption, graphene holds a bright promise because of its excellent electrical properties and low density, but it suffers from poor impedance matching; while the hollow glass microspheres on the other hand have extremely low density and are dielectric. Their synergistic combination could achieve a perfect impedance matching and thus create a novel lightweight absorption composite. The metamaterial structure absorber can efficiently absorb electromagnetic waves over a wide frequency range. This study employs a hydrothermal method to deposit graphene onto the surfaces of hollow glass microspheres, followed by the design of a metamaterial absorber. Upon coating with graphene flakes, the composite material effectively dissipates electromagnetic wave energy through mechanisms such as interfacial polarization, dielectric loss, and the multiple scattering effects of hollow glass microspheres and graphene flakes. The composite exhibits an effective absorption bandwidth up to 4.02 GHz under a graphene flakes mass fraction of 30 %. More importantly, the incorporation of the metamaterial absorber design further significantly enhances the absorption bandwidth to 7.7 GHz. This material demonstrates significant advantages in terms of lightweight and broadband absorption performance, providing new insights for the research of high-performance lightweight and wideband absorbing materials in the future. However, further investigation is required to examine its long-term stability and performance in complex environments.

Development and Characterization of a Flexible Soundproofing Metapanel for Noise Reduction

This study addresses the critical challenge of developing lightweight, flexible soundproofing materials for contemporary applications by introducing an innovative Flexible Soundproofing Metapanel (FSM). The FSM represents a significant advancement in acoustic metamaterial design, engineered to attenuate noise within the 2000–5000 Hz range—a frequency band associated with significant human auditory discomfort. The FSM’s novel structure, comprising a box-shaped frame and vibrating membrane, was optimized through rigorous finite element analysis and subsequently validated via comprehensive open field tests for enclosure-type soundproofing. Our results demonstrate that the FSM, featuring an optimized configuration of urethane rubber (Young’s modulus 6.5 MPa) and precisely tuned unit cell dimensions, significantly outperforms conventional mass-law-based materials in sound insulation efficacy across target frequencies. The FSM exhibited superior soundproofing performance across a broad spectrum of frequency bands, with particularly remarkable results in the crucial 2000–5000 Hz range. Its inherent flexibility enables applications to diverse surface geometries, substantially enhancing its practical utility. This research contributes substantially to the rapidly evolving field of acoustic metamaterials, offering a promising solution for noise control in applications where weight and spatial constraints are critical factors.

Design of lattice metamaterials under the equal strength concept and research on the mechanical properties of their sandwich structures

This study proposes a novel lattice metamaterial with equal strength struts based on the concept of equal strength of beams, which has been designated the strut-enhanced body-centered cubic lattice structure (EBCC). The structure is capable of effectively reducing the stress concentration of the lattice structure at the nodes and increasing the structural energy absorption. The effective elastic properties of EBCC unit cells are investigated in detail under periodic boundary conditions (PBC), and the results show that the deformation response of the unit cell under compressive loading is dominated by bending. A novel sandwich structure, designated S-EBCC, was developed utilizing EBCC as the core material. The effects of geometrical parameters and relative density on the deformation mechanism and mechanical properties of the sandwich structure were analyzed through experiments, numerical simulations and theoretical predictions. The results show that under compressive loading, the stress concentration at the nodes of the EBCC structure is effectively improved and the peak stress is reduced while the energy absorption is increased compared with the traditional S-BCC structure. Under three-point bending load, the larger the strut angle of the S-EBCC structure, the higher the load capacity. Comparison of experimental and theoretical results shows that the failure modes of the S-EBCC structure under both compressive and three-point bending loads are plastic yield.

Designing Connectivity-Guaranteed Porous Metamaterial Units Using Generative Graph Neural Networks

Abstract Designing 3D porous metamaterial units while ensuring complete connectivity of both solid and pore phases presents a significant challenge. This complete connectivity is crucial for manufacturability and structure-fluid interaction applications (e.g., fluid-filled lattices). In this study, we propose a generative graph neural network-based framework for designing the porous metamaterial units with the constraint of complete connectivity. First, we propose a graph-based metamaterial unit generation approach to generate porous metamaterial samples with complete connectivity in both solid and pore phases. Second, we establish and evaluate three distinct variational graph autoencoder (VGAE)-based generative models to assess their effectiveness in generating an accurate latent space representation of metamaterial structures. By choosing the model with the highest reconstruction accuracy, the property-driven design search is conducted to obtain novel metamaterial unit designs with the targeted properties. A case study on designing liquid-filled metamaterials for thermal conductivity properties is carried out. The effectiveness of the proposed graph neural network-based design framework is evaluated by comparing the performances of the obtained designs with those of known designs in the metamaterial database. Merits and shortcomings of the proposed framework are also discussed.

Design of metamaterial for broadband sound absorption through double resonances

Abstract Broadband acoustic absorber via a structure with sub-wavelength thickness is of great and continuing interest in research and engineering communities. To broaden the absorption band of acoustic absorbers, common methods often involve using septum to create a double-layer structure or replacing cavity walls with flexible materials. However, such approaches require strict restrictions of thickness and structure design for the absorbers. This work presents a metamaterial design method that uses an external frame to construct double resonant metamaterials, effectively improving broadband sound absorption performance. Specifically, this method can be decoupled from the design of original cavity-type absorber structure and external frame. The absorption performance is significantly improved by adding an external frame to wrap around a cavity-type acoustic absorber structure with air. Furthermore, utilizing the coaction of cascade coupling and external frame, the average absorption ratio of the metamaterial in high frequency domain (above 2000 Hz) can be improved by 6 times. Since this structural design broadens the absorption band without changing structural parameters of the original absorber, it has potentials to be applied in various engineering fields.

Uncertainty quantification of acoustic metamaterial bandgaps with stochastic material properties and geometric defects

Acoustic metamaterials are a subject of increasing study and utility. Through designed combinations of geometries with material properties, acoustic metamaterials can be built to arbitrarily manipulate acoustic waves for various applications. Despite the theoretical advances in this field, however, acoustic metamaterials have seen limited penetration into industry and commercial use. This is largely due to the difficulty of manufacturing the intricate geometries that are integral to their function and the sensitivity of metamaterial designs to material batch variability and manufacturing defects. Capturing the effects of stochastic material properties and geometric defects requires empirical testing of manufactured samples, but this can quickly become prohibitively expensive with higher precision requirements or with an increasing number of input variables. This paper demonstrates how uncertainty quantification techniques, and more specifically the use of polynomial chaos expansions and spectral projections, can be used to greatly reduce sampling needs for characterizing acoustic metamaterial dispersion curves. With a novel method of encoding geometric defects in a 1D, interpretable, resolution-independent way, our uncertainty quantification approach allows for both stochastic material properties and geometric defects to be considered simultaneously. Two to three orders of magnitude sampling reductions down to ∼100 and ∼101 were achieved in 1D and 7D input space scenarios, respectively. Remarkably, this reduction in sampling was possible while preserving accurate output probability distributions of the metamaterial performance characteristics (bandgap size and location).

Fast inverse design of microwave and infrared Bi-stealth metamaterials based on equivalent circuit model

This work proposed a fast inverse design method for microwave and infrared (IR) bi-stealth metamaterials based on the equivalent circuit model (ECM). Using this method, we designed a microwave and IR bi-stealth metamaterial by deploying a multilayered structure of the indium tin oxide (ITO) film based metasurface. First, the IR emissivity of the ITO film was calculated in the framework of the ECM. Then, an ITO metasurface was proposed to implement low IR emission and high microwave transmission simultaneously. Based on the ECM of the square patch, the ECM of the whole metamaterial was established at the microwave band. An inverse design program was built by incorporating the ECM with genetic algorithm (GA). Structure parameters of the metamaterial were optimized by GA to achieve the broadest microwave stealth bandwidth for the given thickness. Finally, the sample of the optimized bi-stealth metamaterial was prepared and tested. The calculated, simulated, and measured results are in good agreement, showing that such a metamaterial has an IR emissivity of 0.18 in the band from 3 to 14 μm and an efficient microwave stealth band from 4.8 to 17 GHz with a thickness of 4.9 mm. The proposed method will benefit the design and application of microwave and IR bi-stealth metamaterials.

Sound absorption performance of honeycomb metamaterials Inspired by Mortise-and-Tenon structures

To address the limitations of traditional honeycomb sandwich structures in attenuating mid to low-frequency sounds, particularly in configurations with minimal thickness and weight, this study introduces an innovative honeycomb acoustic metamaterial incorporating the traditional Chinese mortise-and-tenon joint. We systematically investigate the acoustic absorption characteristics of the modified honeycomb structure through theoretical analysis, empirical validation, and numerical simulations. Our experimental setup maintained consistent geometric parameters across all trials and demonstrated that the resonance frequency of the modified honeycomb structure decreased by 10 % relative to its conventional counterpart. We conducted detailed analyses on the influence of micropore positioning, tenon geometric dimensions, and micropore diameters on the acoustic performance. Notably, elongating the tenon from 2 mm to 6 mm resulted in a 15 % reduction in resonance frequency, whereas increasing the micropore-to-tenon distance from 0 mm to 4 mm led to a 30 % increase. The integration of the mortise-and-tenon joint significantly enhances the mid to low-frequency sound absorption performance of the honeycomb panels. This improvement is achieved while preserving the structural benefits of low panel thickness and shallow cavity depth, alongside simplified processing of micropores. Our findings elucidate a promising approach to augmenting the acoustic properties of lightweight structural materials, thereby extending their application potential in noise control engineering. This study not only contributes a novel perspective to the design and optimization of acoustic metamaterials but also highlights the potential for integrating traditional architectural techniques with modern material science to enhance noise control solutions.

Investigation of additively manufactured metamaterials for load-bearing structural applications

The study explores the potential application of Triply Periodic Minimal Surface (TPMS) metamaterials in structural engineering and architecture. It evaluates parametric design possibilities and analysis approaches while examining the mechanical properties of five TPMS structures (Gyroid, Schwarz, Diamond, Split, and Neovius). Comparisons are made between Additively Manufactured (AM) samples and numerical simulations. Gyroid and Diamond structures, which display advantageous properties, undergo further investigation with parametric design for uniform and non-uniform lattices. The study proposes simplified analytical formulations for metamaterial design, along with Homogenization analysis and detailed FEM analysis. Compression tests reveal distinct failure modes and stress-strain behaviors for each TPMS. The research suggests further investigation into the influence of the 3D printing process, void detection, and thermomechanical analysis. Finally, the study provides insights into tailored applications of these lattice metamaterials in structural engineering.

Investigating Static and Dynamic Behaviors in 3D Chiral Mechanical Metamaterials by Disentangled Generative Models

AbstractChiral mechanical metamaterials with engineered asymmetric structures have garnered significant interest owing to their potential for manipulating mechanical waves and unconventional mechanical properties. Although several design methodologies have made significant strides in the design and discovery of chiral mechanical metamaterials, 3D designs that incorporate multiple mechanical characteristics remain largely unexplored and the static and dynamic properties of these structures have not received sufficient attention. Here, an innovative approach is introduced for the inverse design of 3D chiral mechanical metamaterials with desired static and dynamic properties, leveraging streamlined shapes to enable a versatile design. By employing conditional generative adversarial networks (c‐GANs), the desired mechanical properties are targeted by focusing on both wave attenuation and stress distribution under compression and shear loading. 3D chiral mechanical metamaterials with additive manufacturing are fabricated to demonstrate the performance of the proposed c‐GAN. Experimental investigations show that the generated structures exhibited a wide range of wave attenuation properties, low stress concentrations, and a variety of stress‐strain curve profiles including nonlinear stiffness, demonstrating their effectiveness in achieving the desired mechanical characteristics. This research offers significant advancements in the on‐demand design capabilities of metamaterials and their applications.

Optimization of acoustic porous material absorbers modeled as rigid multiple microducts networks: Metamaterial design using additive manufacturing

This research presents a strategy to enhancing sound absorption in porous acoustic metamaterials through the optimization of micro-duct networks. The study employs a combination of analytical and numerical methods, systematically adjusting micro-duct diameters within a 2D grid to optimize absorption coefficients at specific frequency bands. The Finite Element Transfer Method (FETM) is utilized for modeling, supported by a multi-objective function influenced by the surface impedance of the network. This approach ensures practical applicability and manufacturability of the designed metamaterial. A significant aspect of the study is the development of an analytical mobility matrix for each microduct, integrated through the Transfer Matrix Method using the visco-thermal dissipation theory. This integration results in a physically coherent model, for which a semi-analytical sensitivity analysis related to the microduct diameters can be directly performed. The optimization employs the Method of Moving Asymptotes (MMA), effectively managing the complexity associated with a large number of design variables. Subsequently, the optimized structure is adapted into a 3D grid, facilitating prototype creation using Additive Manufacturing Technology (AMT) with a specific polymer material. The research methodology is validated through four distinct test cases, each demonstrating the efficacy and adaptability of the optimization tools and techniques. Experimental validation, conducted using an impedance tube, indicates a significant shift in the first absorption maximum from 2500 Hz to 1000 Hz, achieved without altering the material thickness. Additional validation through 3D Finite Element Method (FEM) modeling, which includes visco-thermal effects, further confirms the acoustic efficiency of the final designs. While the potential for achieving lower sub-wavelength conditions is recognized, the study opts for simpler structures, considering the current limitations of 3D printing technology. This study contributes to both theoretical understanding and practical application in acoustic material design, emphasizing the potential for customizing materials to specific frequency ranges. The integration of FETM modeling with MMA provides a systematic and effective approach for optimizing acoustic materials, particularly in enhancing absorption at lower frequencies.

Deep Inverse Design of an Infrared Metasurface Diffuser

AbstractMachine learning (ML) algorithms have become invaluable tools for tackling design challenges associated with achieving unique scattering effects in artificial electromagnetic materials (AEMs). However, their effectiveness is reliant on substantial, well‐constructed training datasets. Building such datasets using traditional methods becomes impractical for increasingly complex and large‐scale geometric models. Achieving a specific diffuse scattering is one example and this often requires electrically large and diverse AEM arrays. Unfortunately, while numerical simulations offer high accuracy by utilizing fine meshing, their computational limitations render them incapable of handling such large structures and computing their scattering parameters efficiently. This work proposes a new approach to overcome these limitations by replacing conventional numerical simulations with a hybrid method that combines electromagnetic simulations with an analytical model, enabling the rapid and accurate generation of datasets for electrically large metamaterial arrays. Utilizing this approach, an optimized metasurface geometry for the mid‐infrared range is successfully identified and tested that exhibits desirable diffuse scattering effects. This innovative method paves the way for significantly faster design and optimization of metamaterials, while also unlocking the potential for a new generation of large‐scale, high‐quality ML datasets for AEM problems.

Crafting shape-changing experiences: emotional evaluation of morphing metamaterials

ABSTRACT We introduce a novel approach to evaluate how the design properties of morphing metamaterial influence shape-changing experiences. We leverage parametric design to create cutting patterns that change the Density and Geometry material properties. Using laser-cutting, we apply the patterns to a non-stretchable woven textile, resulting in a stretchable metamaterial that we actuate using an electromagnetic coil. This systematic design approach leads to programmatic control over the material movement, making it suitable for controlled evaluation of perceived experience. In a 2×2 mixed-method study, we assess how the metamaterial’s Density and Geometry properties impact the observed experience. Our findings indicate that such changes significantly and independently affect participants’ perceived emotions, mood, associations, and preferences. Our research contributes to the body of work of systematic studies in the shape-changing community. By using our morphing metamaterial design and implementation technique, coupled with our controlled evaluation of specific design properties, we have revealed new insights about the influencing factors of shape-changing experiences. We have incorporated these insights into our morphing metamaterial design guidelines, which outline the impact of Density and Geometry properties on an observer’s perceived emotions. We hope our work will open up new possibilities for expressive, evocative metamaterial-focused shape-changing experiences.

Efficient Study on Westervelt-Type Equations to Design Metamaterials via Symmetry Analysis

Metamaterials have emerged as a focal point in contemporary science and technology due to their ability to drive significant innovations. These engineered materials are specifically designed to couple the phenomena of different physical natures, thereby influencing processes through mechanical or thermal effects. While much of the recent research has concentrated on frequency conversion into electromagnetic waves, the field of acoustic frequency conversion still faces considerable technical challenges. To overcome these hurdles, researchers are developing metamaterials with customized acoustic properties. A key equation for modeling nonlinear acoustic wave phenomena is the dissipative Westervelt equation. This study investigates analytical solutions using ansatz-based methods combined with Lie symmetries. The approach presented here provides a versatile framework that is applicable to a wide range of fields in metamaterial design.

Click metamaterials: Fast acquisition of thermal conductivity and functionality diversities

In material science, the development of metamaterials is crucial for advancing various technological applications. However, most metamaterial designs are still case by case due to lacking a fundamental mechanism for achieving reconfigurable thermal conductivities, largely hindering design flexibility and functional diversity. Inspired by the principles of click chemistry, known for its modular and efficient approach to creating molecular diversity, here we propose a universal concept of click metamaterials for fast realizing various thermal conductivities and functionalities. Tunable hollow-filled unit cells are constructed as the modified building blocks to change the thermal conductivity locally. Different configurations of unit cells with variable fill fractions can generate convertible thermal conductivities from isotropy to anisotropy, allowing click metamaterials to exhibit environment-free and reconfigurable thermal functionalities. The straightforward structures enable full-parameter regulation and simplify engineering preparation, making click metamaterials a promising candidate for practical use in other diffusion and wave systems.

Periodicity alters topological states in thermal diffusion system

Topological edge states are a ubiquitous phenomenon across diverse wave systems, including electromagnetic, acoustic and quantum systems. In contrast to wave systems, thermal transport is a kind of diffusion system characterized by pure dissipation. The imposition of different boundary conditions can significantly influence the evolution of thermal system, leading to the appearance of different topological states, which haven't been systematically analyzed yet, especially in practical heat transfer structures. In this work, via a non-Hermitian thermal diffusion lattice model, we discuss the periodicity-dependent topological states. Through rigorous theoretical analysis and numerical simulations of the temperature field, the Hamiltonian is obtained whose eigenvalues are purely imaginary corresponding to the decay rate of the temperature field. Our work paves the way for the investigation of how periodicity alters topological states in thermal diffusion systems, potentially revolutionizing the design of thermal metamaterials for topological thermal protection in thermal management.

Unprecedented mechanical wave energy absorption observed in multifunctional bioinspired architected metamaterials

In practical engineering, noise and impact hazards are pervasive, indicating the pressing demand for materials that can absorb both sound and stress wave energy simultaneously. However, the rational design of such multifunctional materials remains a challenge. Herein, inspired by cuttlebone, we present bioinspired architected metamaterials with unprecedented sound-absorbing and mechanical properties engineered via a weakly-coupled design. The acoustic elements feature heterogeneous multilayered resonators, whereas the mechanical responses are based on asymmetric cambered cell walls. These metamaterials experimentally demonstrated an average absorption coefficient of 0.80 from 1.0 to 6.0 kHz, with 77% of the data points exceeding the desired 0.75 threshold, all with a compact 21 mm thickness. An absorptance-thickness map is devised for assessing the sound-absorption efficiency. The high-fidelity microstructure-based model reveals the air friction damping mechanism, with broadband behavior attributed to multimodal hybrid resonance. Empowered by the cambered design of cell walls, metamaterials shift catastrophic failure toward a progressive deformation mode characterized by stable stress plateaus and ultrahigh specific energy absorption of 50.7 J/g—a 558.4% increase over the straight-wall design. After the deformation mechanisms are elucidated, a comprehensive research framework for burgeoning acousto-mechanical metamaterials is proposed. Overall, our study broadens the horizon for multifunctional material design.

Low-Frequency Sound-Insulation Performance of Labyrinth-Type Helmholtz and Thin-Film Compound Acoustic Metamaterial.

This paper presents a type of acoustic metamaterial that combines a labyrinth channel with a Helmholtz cavity and a thin film. The labyrinth-opening design and thin-film combination contribute to the metamaterial's exceptional sound-insulation performance. After comprehensive research, it is observed that in the frequency range of 20-1200 Hz, this acoustic metamaterial exhibits multiple sound-insulation peaks, showing a high overall sound-insulation quality. Specifically, the first sound-insulation peak is 26.3 Hz, with a bandwidth of 13 Hz and giving a transmission loss of 56.5 dB, showing excellent low-frequency sound-insulation performance. To further understand the low-frequency sound-insulation mechanism, this paper uses the equivalent model method to conduct an acoustic-electrical analogy, construct an equivalent model of the acoustic metamaterial, and delve into the sound-insulation mechanism at the first sound-insulation peak. To confirm the validity of the theoretical calculations, physical experiments are carried out by 3D printing experimental samples. The analysis of the experimental data has yielded results that are consistent with the simulation data, providing empirical evidence for the accuracy of the theoretical model. The material has significant practical application value. Finally, various factors are studied in depth based on the established equivalent model, which can provide valuable insights for the design and practical engineering application of acoustic metamaterials.

High-Throughput On-Demand Design Platform for Plasmonic Nanocavities: A Wavefunction Theory Approach.

Surface plasmon polaritons from plasmonic nanocavity have aroused great interest due to their applications in various fields, in which on-demand design is hindered by the lack of theoretical frameworks. Herein, based on its wave nature, we developed a wavefunction theory to explicitly describe individual surface plasmon polaritons and the resultant near-field and far-field behaviors, which serves as an efficient platform for high-throughput on-demand design of nanocavities. We found an applicative wavefunction form and proposed a two-body interaction function and a "shell" model for many-body interactions in surface plasmon polaritons' coupling. The wavefunction of individual surface plasmon polaritons and resultant near-field and far-field behaviors can be given explicitly and precisely. The theory provides a fundamental and quantitative understanding of surface plasmon polaritons and enables highly efficient on-demand design of plasmonic metamaterials and devices, leading to further methodological applications in numerous aspects.

Metamaterial structure design based on genetic algorithm and phase change material GST for multispectral camouflage

This study proposes a multispectral camouflage tunable multilayer film metamaterial (TMFM) with thermal management function based on genetic algorithm (GA), which is composed of ZnS/YbF3/Ge/Ge2Sb2Te5 (GST)/Au multilayer film. Through numerical analysis, we assess its efficacy in visible-infrared compatibility camouflage and radiative heat dissipation. Within the visible light band, different structural colors can be produced by adjusting the thickness of the ZnS film. The average emissivity within the 3–5 μm and 8–14 μm infrared bands is measured at 0.04 and 0.14, respectively. The low emissivity facilitates effective thermal management. Moreover, an average emissivity of 0.52 within the 5–8 μm range is instrumental in achieving efficient radiation heat dissipation. Laser stealth capability is further enhanced, with an emissivity reaching 0.70 at 10.6 μm. Therefore, this metamaterial structure has broad application prospects in both military and civilian industrial fields.