Search Results (417)

Traditional homogeneous materials often face an inherent trade-off between strength and toughness, restricting their application in high-performance impact protection. Mechanical metamaterials overcome this fundamental limitation by integrating structure and material. The 3D-printed Bouligand laminates (3DPBLs), a type of mechanical metamaterial, are renowned for their exceptional impact resistance. While the 3DPBLs have been proven to provide superior resistance under normal impact, actual service conditions inevitably involve complex, multi-directional loading. We aimed to investigate the 3DPBLs’ oblique impact resistance here. To this purpose, samples of 3DPBLs with varying helical angles (0°, 7°, 15°, 60°, 90°) were fabricated and subjected to low-velocity drop-weight impact tests at impact angles of 0°, 30°, 45°, and 60° to evaluate their damage evolution and energy dissipation. The experimental investigation exhibited distinct temporal evolutions of contact forces, with the 15° helical configuration identified as the optimal design. Further numerical analysis using a finite element model (validated with a deviation < 10%) is conducted to simulate performance under diverse impact angles in order to validate the reasonability of the experimental investigation. Mechanistically, 3DPBLs enhance impact resistance by increasing fracture tortuosity through their periodically rotated layered structure. These findings establish a theoretical foundation for developing high-performance, lightweight, and toughened protective materials. Full article

This study investigates the structural behavior of metamaterial sandwich panels with Bézier-based lattice cores using parametric finite element modeling. Geometric parameters were varied to assess their influence on mass, stress, and energy absorption capabilities. Ligament thickness was found to strongly affect mass, while curvature influences stress and deformability. The optimization results outline a set of optimal design solutions, enabling selection of configurations based on specific performance priorities. The proposed workflow provides a robust strategy for designing mechanically efficient structures suitable for advanced engineering applications. Full article

Metamaterials possess unique and desirable multiphysical behaviors derived from deliberately arranging conventional materials into designed structural topologies. Multifunctional mechanical metamaterials that can both carry load and provide in situ state awareness are increasingly needed for applications such as structural health monitoring and soft robotic systems. To address the demand for multifunctional metamaterials, this study reports a scalable fabrication strategy for self-sensing lattice metamaterials by conformally dip-coating 3D-printed flexible cells with a carbon nanotube (CNT)–styrene–ethylene–butylene–styrene (SEBS) nanocomposite. Scanning electron microscopy shows that the coating conforms closely to the printed struts with well-dispersed CNT networks. The electromechanical behavior of coated Octet, Kelvin, and auxetic unit cells was characterized under quasi-static cyclic uniaxial compression (0–40% strain). All the coated structures exhibited highly stable, reversible, and repeatable piezoresistive response, with a near-linear relationship between resistance change and strain. Among the tested geometries, the auxetic unit cell achieved the highest strain sensitivity that was approximately four times that of the Octet cell and six times that of the Kelvin cell. To evaluate scalability, auxetic lattices containing eight scaled auxetic unit cells were shown to retain high sensitivity and remained statistically similar to the unit cell. This study demonstrates that the strain sensing performance of nanocomposites can be engineered through lattice topology using a simple dip-coating functionalization approach, enabling scalable self-sensing metamaterials for large-scale and conformal sensing applications. Full article

Polymer-based systems have been shown to have a particular combination of characteristics that make them desirable in technological sectors, such as lightness, insulating properties, and easy molding during processing, as well as mechanical versatility, which is greatly due to their molecular microstructure. Nevertheless, they still present limitations in mechanical performance and use at moderate/high temperatures, considerably restricting their range of applications. Thus, great efforts have been directed towards developing strategies intended to enhance said characteristics and predict their complex mechanical behavior, with the main goal of adapting their properties to the end-use application. The present review considers the most recent developments, focusing on the research published in 2025 and early 2026, and future challenges in the mechanical behavior of polymer-based materials, being structured according to material considerations, more specifically the development of advanced (nano)composites based on high-performance matrices and functional nanoparticles, as well as bio-based polymer (nano)composites obtained from renewable sources and multifunctional smart and meta-materials for monitoring and long-term use; the development of new processing methods, focusing on advanced additive manufacturing; and the use of artificial intelligence and machine learning. All in all, the final objective is generating knowledge that will enable the preparation of components with tailor-made mechanical characteristics and functional properties, covering material design and processing. Full article

Magnetic metals are of considerable importance for stealth technology and electromagnetic pollution control. However, they suffer from inherent limitations, such as the Snoek limit and narrow absorption bandwidth, which restrict their applications in complex scenarios. To address these challenges, this review systematically summarizes the recent advances of magnetic metal-based microwave-absorbing materials (MAMs), focusing on four core directions: alloy design, composite engineering, structural regulation, and preparation technology. The intensity and frequency bands of absorption in alloys are dictated by the material’s composition as well as its structural attributes. Moreover, composite systems incorporating carbon materials, MXenes, oxides, ceramics, and conductive polymers are discussed, where the synergistic design of components optimizes impedance matching and loss mechanisms. Key structural design strategies include core-shell structures, interface engineering, self-assembled hierarchical structures, and macroscopic structural design. These structures achieve the synergistic improvement of thin, lightweight, broadband, and strong absorption performance by enhancing interface polarization, multiple scattering, and resonance effects, while endowing materials with excellent environmental stability. Notably, metamaterial-based designs can further achieve an ultrawide bandwidth spanning 0.3–18 GHz. Additionally, preparation processes are crucial for regulating the microstructure and activating loss mechanisms. This review aims to offer theoretical and practical insights for developing high-performance, multifunctional magnetic MAMs. Full article

Honeycomb structures are widely utilized in engineering due to their light weight, high strength, high stiffness, excellent energy absorption, and outstanding vibration isolation performance. In this study, we propose a novel tuning fork–honeycomb megastructure, which demonstrates excellent tunable vibration isolation capabilities. The geometric configuration of the structure before and after shape memory–induced deformation is described, and a theoretical model for the natural frequency of the initial configuration is established. The vibration isolation performance of the structure is validated through simulations and experiments, and three strategies for tuning its vibrational behavior are proposed. First, by exploiting variable stiffness, shape memory materials are used to achieve a linear shift in the bandgap position. At 75 °C, the starting frequency of the bandgap decreases to 95% of its value at room temperature. Second, based on shape memory programming, the deformed structure exhibits a 20% reduction in the center frequency of the first bandgap and a 47% reduction in the center frequency of the second bandgap compared to the undeformed configuration. Then, by altering the geometry of the tuning fork structure, in–plane deformation is shown to provide superior low–frequency vibration isolation performance compared to out–of–plane deformation. Finally, the design method of programmable mechanical pixel metamaterials is introduced. This method achieves tunable full–band vibration isolation through shape–memory–induced deformation and temperature–induced stiffness variation. It enhances the structural diversity, modularity, and reconfigurability. Moreover, a shape memory tuning fork structure could be combined with any type of cellular structure with excellent vibration isolation performance. It offers a new paradigm for designing structures with adjustable wide–frequency vibration isolation performance. Full article

This paper introduces a vanadium dioxide-integrated broadband metamaterial absorber designed for the terahertz frequency range. The simulation results for the proposed structure demonstrate a wide 90% absorption bandwidth of 8.23 THz, corresponding to a fractional bandwidth of 89.5%. By leveraging the phase-transition properties of VO₂, the absorber demonstrated dynamic adjustability by modulating the absorption from 3% to 98.74%. The absorption mechanism was analyzed through the impedance matching theory and electromagnetic field distributions, confirming the role of magnetic resonance and interference. Furthermore, machine learning algorithms, specifically Linear Regression, Support Vector Regression, and Random Forest (RF), were applied to accelerate the design process and optimize the structural parameters. Among these, the RF model demonstrated superior prediction accuracy. The machine learning-assisted optimization successfully extended the effective absorption bandwidth to 9 THz, representing an improvement by 9.4% compared to the traditional optimization methods. These results validate the efficacy of combining electromagnetic simulation with data-driven techniques for advanced metamaterial design. Full article

A compact and polarization-insensitive hexa-band metamaterial absorber (MMA) is designed, fabricated, and experimentally validated for S, C, X, and Ku band applications. The proposed unit cell consists of two square rings, two hexagonal rings, and two diamond-shaped copper resonators printed on an FR-4 dielectric substrate with a thickness of 1.6 mm. The structure exhibits six distinct absorption peaks at 2.178, 5.484, 8.391, 11.811, 15.858, and 18.689 GHz, with corresponding absorptivities of 99%, 98%, 99%, 99%, 99%, and 97%, respectively. The compact unit cell of 12.5 × 12.5 mm² achieves high absorption efficiency due to strong electromagnetic coupling among the resonators. Simulated and measured results show strong agreement, confirming the accuracy of the design. Owing to its four-fold symmetric geometry, the absorber maintains stable performance under varying polarization angles and incidence angles up to 60° for both TE and TM polarizations. The electric field, magnetic field, and surface current distributions are analyzed to explain the absorption mechanism at each resonant frequency. The proposed MMA demonstrates multiband functionality, angular stability, and high absorptivity within a simple and low-cost design, making it a promising candidate for stealth, air traffic control, and satellite communication applications. Full article

Programmable mechanical metamaterials enable precise regulation of mechanical responses through geometric design, ushering in transformative paradigms for transformable structures. To systematically map the knowledge landscape and development trends in this field, this study employs knowledge mapping methods to analyze the current research status, core hotspots, and future directions of programmable mechanical metamaterials. During the research process, we expanded keywords using the litsearchr tool to optimize the retrieval strategy. Bibliometric tools, including CiteSpace 6.3.R3 and bibliometrix, were utilized to conduct multidimensional analyses on 2017 original papers related to mechanical metamaterials in transformable architecture from 2015 to 2025. These analyses encompass co-word analysis, co-citation clustering, and structural variation analysis. Key aspects include (1) identifying core journals and their attributes to clarify interdisciplinary dynamics, (2) mapping research themes and evolutionary trends through keyword analysis and clustering, and (3) pinpointing research hotspots and future directions based on citation networks and clustering results. The results reveal significant interdisciplinary characteristics, with core knowledge emerging from the intersection of materials science, mechanics, and civil engineering. Mathematical system theory provides a cross-scale modeling foundation for metamaterial microstructure design. The field is evolving from static structural design toward environment-adaptive intelligent systems. Future efforts should prioritize multi-physics collaborative regulation, engineering integration, and technical chain refinement. These findings offer a theoretical reference for the innovative development of transformable architecture. Full article

This work explores the mechanical responses of 3D-printed periodic arch-inspired structures (PASs) and PASs doped with NdFeB powder to advance their application in lightweight structural load-bearing and future structure–function integration. Three PAS configurations were fabricated via digital light processing (DLP), and magnetic PASs (MPASs) were produced by dispersing NdFeB powder (1–3 g/200 mL) into photosensitive resin. Under quasi-static compression, key mechanical properties—Young’s modulus (E), yield strength (σ_y), and compressive strength (σ_c)—of non-magnetic PASs increase linearly with relative density (ρ* = 0.18–0.48): for PAS22, E rises from 68.1 to 200.3 MPa (+194%), σ_y from 2.18 to 6.75 MPa (+210%), and σ_c from 2.98 to 9.07 MPa (+204%). Under dynamic impact (~100 s⁻¹), mechanical enhancement is even more pronounced: E of PAS22 surges to 814.8 MPa (3.2× higher than quasi-static), and σ_c reaches 11.54 MPa. Finite element simulations reveal that the Ideal Plastic Model best predicts quasi-static brittle fracture, whereas the Hardening Function Model captures dynamic behavior most accurately. Stress and plastic strain concentrate at the straight–arc junctions—identified as critical weak points. MPASs exhibit higher stiffness and yield strength (e.g., E of MPAS22 up to 896.5 MPa under impact) but lower compressive strength (e.g., 11.01 MPa vs. 11.54 MPa for NMPAS22), attributed to NdFeB-induced brittleness that shifts the failure mode from “local damage accumulation” to “rapid overall failure”. This study establishes quantitative doping–structure–property correlations, providing design guidelines for next-generation functional arch-inspired metamaterials toward magnetically responsive, load-bearing applications. Full article

Metamaterials (MMs)-based terahertz (THz) biosensors hold promise for clinical diagnosis, featuring label-free operation, simple, rapid detection, low cost, and multi-cell-type discrimination. However, liquid around cells causes severe interference to sensitive detection. Most existing MMs-based cell biosensors detect dead cells without culture medium (losing original morphology), hindering stable, sensitive multi-cell discrimination. Here, a terahertz biosensor composed of a microcavity and MMs can be used to detect and discriminate multiple cell types within suspension. Its detection mechanism relies on cellular size (radius)/density in suspension, which induces effective permittivity (ε_eff) differences. By designing MMs’ split rings with luxuriant gaps, the biosensor achieves a theoretical sensitivity of ~328 GHz/RIU, enabling sensitive responses to suspended cells. It shows a robust, increasing frequency shift (610–660 GHz) over 72 h of cell apoptosis. Moreover, it discriminates nerve cells, glioblastoma (GBM) cells, and their 1:1 mixture with obviously distinct frequency responses (~650, ~630, ~620 GHz), which suggests effective and reliable multi-cell-type recognition. Overall, this study and its measurement method should pave the way for metamaterial-based terahertz biosensors for living cell detection and discrimination, and this technology may inspire further innovations in tumor investigation and treatment. Full article

To address the challenges of high computational costs, susceptibility to local optima, and heavy reliance on manual intervention in multi-physics parameter optimization for symmetric acoustic metamaterials, an enhanced Chimp Optimization Algorithm (DADCOA) is proposed in this paper. This algorithm integrates the double chaotic initialization strategy (DCS), adaptive multimodal convergence mechanism (AMC), and dual-weight pinhole imaging update operator (DWPI). It employs a Logistic–Tent composite chaotic mapping strategy for population initialization, significantly enhancing distribution uniformity within high-dimensional parameter spaces. An AMC factor is then introduced to dynamically balance global exploration and local exploitation based on the real-time evolutionary state of the population. A dual-weight population update mechanism, incorporating distance and historical contributions, is integrated with a pinhole imaging opposition-based learning strategy to improve population diversity. Additionally, a composite single objective error feedback local differential mutation operation is introduced to improve optimization accuracy for coupled multi-physics objectives. Experimental validation based on the CEC 2022 test function suite and an acoustic metamaterial parameter optimization model demonstrates that compared to the standard COA algorithm and existing improved algorithms, the DADCOA algorithm reduces simulation time by 28.46% to 60.76% while maintaining high accuracy. This approach effectively addresses the challenges of high computational cost, stringent accuracy requirements, and composite single objective coupling in COMSOL physical parameter optimization, providing an effective solution for the design of acoustic metamaterials based on symmetric structures. Full article

Light carrying orbital angular momentum (OAM) has emerged as a promising tool for manipulating light–matter interactions, providing an additional degree of freedom to explore chiral-optical phenomena at the nanoscale. When such vortex beams interact with chiral metamaterials, a unique phenomenon of optical asymmetry known as vortical dichroism (VD) arises. Nevertheless, most existing chiral metamaterials exhibit limited VD responses, and the underlying physical mechanisms are yet to be fully clarified. In this work, we propose three-dimensional spiral metamaterials that achieve gigantic VD effect. This pronounced VD effect originates from the intrinsic coupling between the spiral structure and the chirality inherent to optical vortices, which leads to strongly asymmetric scattering intensities for left- and right-handed OAM beams of opposite topological charges. Numerical simulations confirm a remarkable VD value of 0.69. Further analysis of electric field distributions reveals that the asymmetric VD response stems from a handedness-dependent excitation of distinct electromagnetic modes. For opposite handedness, spatial mode mismatch results in enhanced scattering. In contrast, matching handedness enables efficient energy coupling into a guided spiral mode, which suppresses scattering. These findings not only deepen the physical understanding of VD mechanisms but also establish a versatile platform for developing advanced chiral photonic devices and enhancing OAM-based light–matter interactions. Full article

In recent years, achieving ultra-wideband electromagnetic absorption has emerged as a critical challenge in confronting advanced broadband electromagnetic detection technologies. This capability is essential for effectively countering sophisticated radar systems. In this study, we present a novel multilayer metamaterial absorber that integrates an FR4 transmission layer, a periodic gradient dielectric structure designed for resonant impedance matching, and a magnetic skin layer for enhanced energy dissipation. By employing asymptotic gradients in both structure and composition, this design achieves dual-gradient electromagnetic parameter modulation, enabling efficient absorption across the X, Ku, and K bands (8.6–26.4 GHz) with a total thickness of 3.5 mm (effective thickness: 2 mm) and a density that is one-third that of conventional magnetic metamaterials. The proposed absorber demonstrates polarization insensitivity, stability across wide incident angles (up to 60°), and an absorption efficiency of 94%, as confirmed by full-wave simulations and experimental validation. Moreover, the fiber-reinforced hierarchical structure addresses the traditional trade-off between broadband absorption performance and mechanical load-bearing capacity. Full article

Two-photon polymerization (2PP) is revolutionizing micro- and nanoscale manufacturing by enabling true 3D fabrication with feature sizes far below the diffraction limit—capabilities that traditional lithography cannot match. By using ultrafast femtosecond laser pulses and nonlinear absorption, 2PP initiates polymerization only at the laser’s focal point, offering unmatched spatial precision. This paper highlights key advancements driving the field forward: the development of new materials engineered for 2PP with improved sensitivity, mechanical strength, and the introduction of high-speed, parallelized fabrication strategies that significantly enhance throughput. These innovations are shifting 2PP from a prototyping tool to a viable method for scalable production. Applications now range from custom biomedical scaffolds to complex photonic and metamaterial structures, demonstrating their growing real-world impact. We also address persistent challenges—including slow writing speeds and limited material options—and explore future directions to overcome these barriers. With continued progress in materials and hardware, 2PP is well positioned to become a cornerstone of next-generation additive manufacturing. Full article