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In this paper, a polarization-insensitive magnetic tunable perfect metamaterial absorber is analyzed which shows its functionality as a refractive index (RI) sensor. The unit cell structure of reported absorber consists of a cross-shaped Indium Arsenide (InAs) array over aluminum ground plane and has dimensions less than λ c / 4 with thickness of 7.5 μ m and periodicity of 9 μ m making it an ultra-thin absorber. The proposed absorber provides an average absorption of 99.99% on the implementation of magnetic field (B) at 0.4 T. The resonance frequency and corresponding absorption rates can be controlled by varying the magnetic field from B = 0. 1 –0.4 T which provides high absorption as well as shift in the frequency spectrum by 0.3 THz/T. Additionally, parametric analysis has also been done to confirm the selection of the optimum value of the designed parameters of the structure. Furthermore, simulation results reveal that the proposed structure is very sensitive to the change of RI values in the surroundings thus, the proposed structure can be employed as a RI sensor high sensitivity of 1.083 THz/RIU over the range of 1–1.6 RI. In addition, the result shows that the sensor can detect different chemical compounds such as ethanol, gasoline, paraffin, sodium chloride, carbon disulfide with an average sensitivity of 0.925 THz/RIU. Thus, the proposed absorber with obtained sensitivity can be utilized as a biochemical sensor, making it one of the best contenders for chemical industry uses in diagnosis of different hazardous chemicals as well as finding its applicability in biomedical uses. [ABSTRACT FROM AUTHOR]

Metamaterial design approaches, which integrate structural elements into material systems, enable the control of uncommon behaviours by decoupling local and global properties. Leveraging this conceptual framework, metamaterial adhesives incorporate nonlinear cut architectures into adhesive films to achieve unique combinations of adhesion capacity, release, and spatial tunability by controlling how cracks propagate forward and in reverse directions during separation. Here, metamaterial adhesive designs are explored with triangular cut features while integrating hierarchical and secondary cut patterns among primary nonlinear cuts. Both cut geometry and secondary cut features tune adhesive force capacity and energy of separation. Importantly, the size and spacing of cut features must be designed around a critical length scale. When secondary cut features are greater than a critical length, cracks can be steered in multiple directions, going both forward and backwards within a primary attachment element. This control over crack dynamics enhances the work of separation by a factor of 1.5, while maintaining the peel force relative to a primary cut. If hierarchical cut features are too small or too compliant, they interact and do not distinctly modify crack behaviour. This work highlights the importance of adhesive length scales and stiffness for crack control and attachment characteristics in adhesive films. This article is part of the theme issue 'Origami/Kirigami-inspired structures: from fundamentals to applications'. [ABSTRACT FROM AUTHOR]

This paper presents the detailed design configuration and investigation of a small-scale dual-band metamaterial absorber (MTMA) for solid and liquid sensing applications. The overall dimension of the MTMA unit cell is 10 × 10 × 1.57 mm3 and constitutes an affordable FR-4 substrate. The absorber exhibits dual absorption peaks at 3.470 GHz for the S-band and 7.219 GHz for the C-band, respectively. Both absorption characteristics have been validated through comprehensive simulation and experimental procedures. The dual-band absorption rate exceeded 99% during simulations, and experimental validation showed an absorption rate above 98%. For sensing applications, various solid materials, including different Rogers substrates (RT 5880, RT 5870, RT 4003 and RT 4835) and liquids such as sunflower and crown oil, were utilized. Our findings indicate that the proposed MTMA achieves a maximum Q-factor of 191 and a sensitivity of up to 2.5 for both solid and liquid sensing applications compared to previous studies. The simulation and experimental validation of the result indicate that suggested MTMA can be effectively used in different sensing applications such as the medical and communications industry. [ABSTRACT FROM AUTHOR]

Electromagnetic (EM) absorbers are specially designed structures that dissipate the absorbed EM energy into heat by minimizing the reflection as well as transmission. The absorbers operating in microwave and millimetre wave regimes have been found essential in applications such as radar, communication systems, EM interference prevention, and stealth technologies. Design concepts such as Salisbury, Jaunman screens, and impedance-matching layers are discussed. As a game-changing innovation in wave attribute manipulation, metamaterial behaviour provides an unprecedented command over how waves interact with matter. This review examines the significant hurdles and restrictions metamaterial absorbers must overcome, like fabrication, the tradeoff between absorption bandwidth and thickness, and material losses. Broadband absorption, tunability, and feasibility of producing thin, lightweight absorbers all contribute to their desirability for various applications. Different losses responsible for the absorption phenomena are detailed for both narrowband and broadband cases. This critical analysis highlights the enormous promise of metamaterial absorbers while emphasizing the ongoing research efforts needed to overcome the associated obstacles. Its goal is to advance state-of-the-art designs by critically assessing the existing status of the field, thereby guiding future research, development, making it easier to implement microwave and millimetre wave absorbers in a wide range of real-time applications. [ABSTRACT FROM AUTHOR]

The spatiotemporally-nonlocal phenomena in heat conduction become significant but challenging for metamaterials with artificial microstructures. However, the microstructure-dependent heat conduction phenomena are captured under the hypothesis of spatiotemporally local equilibrium. To capture the microstructure-dependent heat conduction phenomena, a generalized nonlocal irreversible thermodynamics is proposed by removing both the temporally-local and spatially-local equilibrium hypotheses from the classical irreversible thermodynamics. The generalized nonlocal irreversible thermodynamics has intrinsic length and time parameters and thus can provide a thermodynamics basis for the spatiotemporally-nonlocal law of heat conduction. To remove the temporally-local equilibrium hypothesis, the generalized entropy is assumed to depend not only on the internal energy but also on its first-order and high-order time derivatives. To remove the spatially local equilibrium hypothesis, the thermodynamics flux field in the dissipation function is assumed to relate not only to the thermodynamics force at the reference point but also to the thermodynamics force of the neighboring points. With the developed theoretical framework, the thermodynamics-consistent spatiotemporally-nonlocal models can then be developed for heat transfer problems. Two examples are provided to illustrate the applications of steady-state and transient heat conduction problems. [ABSTRACT FROM AUTHOR]

This paper presents a novel metamaterial absorber designed to function effectively across the S, C, X, and Ku frequency bands (2–18 GHz). The unit cell of the metamaterial absorber is derived from an edge-intruded triangular structure, exhibiting multiple resonances. It is thoughtfully designed to achieve fourfold symmetry, ensuring polarization insensitivity. The proposed structure, fabricated on an FR4 substrate with a metallic ground plane, demonstrates exceptional absorption peaks at 2.5 GHz (97%), 3.4 GHz (96.5%), 5.2 GHz (99%), 9.07 GHz (98.8%), 12 GHz (98.1%), 13.66 GHz (89.1%), and 16 GHz (98.9%). The absorber’s four-fold symmetric design ensures polarization insensitivity, while its ultra-thin profile (0.013 λ ) offers several practical benefits. By harnessing the unique properties of near-zero refractive index (NZRI) metamaterials, this absorber has the capability for precise control over electromagnetic waves. Its outstanding performance and versatility position it as a strong candidate for applications such as wavefront shaping, beam steering, sensing, and electromagnetic cloaking.Article Highlights: Investigation on the feasibility of a novel Near-Zero Refractive Index (NZRI) metamaterial designed to function effectively across a broad frequency band. Theoretical exploration of the absorption mechanisms at play in metamaterial structures. An in-depth exploration of the metamaterial absorber, involving extensive computer simulations, detailed result interpretation, and rigorous experimental validation. [ABSTRACT FROM AUTHOR]

Copyright of Micronanoelectronic Technology is the property of Micronanoelectronic Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a high‐gain wearable circularly polarized bow‐tie antenna (WCPBTA) with metamaterial unit‐cells and 5 pins (5Ps) technique for telemedicine applications such as telemonitoring the elderly or the patients especially for emergency conditions of contagious diseases. The frequency range of the proposed antenna is 5.725–5.850 GHz, which belongs to the unlicensed‐national information infrastructure (U‐NII‐3) for the industrial, scientific, and medical (ISM) sub‐channels. A light‐weight and flexible felt with dielectric constant εr = 3, thickness 1.27 mm, and tan (δ) = 0.0095 is used as the substrate for patient comfort and wearability. The overall dimensions of the proposed antenna are 64 × 62 × 1.27 mm3 or 0.102 λg3 at 5.8 GHz. The maximum simulated gain at 5.8 GHz is 8.25 dB, which is more than 4 dB compared to that of the original bow‐tie antenna. Besides, the axial ratio (AR) and the specific absorption rate (SAR) are also analyzed, which meet the perfect requirement for medical applications. The fabricated prototype of the antenna shows good compatibility between simulation and measurement results. These characteristics make the proposed WCPBTA a good choice for wireless body area networks (WBANs) in telemonitoring applications especially with the aim of preventing the spread of contagious diseases. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metals is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

AbstractThis paper introduces a novel methodology for predicting the acoustic absorption coefficient of DENORMS cell based acoustic metamaterial. The samples were printed from resin using Digital Light Processing based 3D printing technique. The manufactured samples were tested in an Impedance tube using the two Microphone method. A virtual simulation test rig was used to generate data sets for geometrically distinct DENORMS cell based metamaterial. Four distinct soft computing techniques specifically the “Neural Networks (NN), Random Forests (RF), Decision Trees (Rpart) and Generalized Linear Model (GLM)”, were employed and compared to develop an accurate prediction model for forecasting the absorption coefficient of the developed metamaterial. The machine learning techniques were used due to their higher speed and lower computational power requirement compared to numerical simulations to determine the absorption coefficient. The input variables consist of the Spherical Diameter, Cylindrical Diameter, Cylinder Length of the DENORMS cell and Frequency of Incident noise. The performance of the four prediction models was evaluated based on criteria such as Root mean square error, Coefficient of determination, Correlation and Accuracy. Ten-Fold cross validation is performed to test the robustness of the model. [ABSTRACT FROM AUTHOR]

This paper elaborates on the wave propagation characteristics of a smart sandwich plate consisting of smart piezo composite layers on a plate's upper and lower borders via an auxetic core. This study's equation of motion was derived using a refined version of the Shear-deformation theory at a higher order, or HSDT. Additionally, detecting the properties of the auxetic core and piezoelectric composite layers employs a micromechanical model. The fundamental equations of the smart sandwich plates were formulated utilizing the Hamiltonian principle and Maxwell's law. Then, the governing equations of a sandwich plate are solved using an exponential form and an analytical method. Furthermore, the phase velocity of the intelligent sandwich plate is provided based on the layer thicknesses of the auxetic core and thicknesses of intelligent piezoelectric composite layers. In addition, each figure calculates and presents the weight of the Winkler–Pasternak coefficient, the viscoelastic substances factor, the source of the outside electricity, and the volume percent of reinforcement in the matrix on the phase velocity. [ABSTRACT FROM AUTHOR]

Abstract\nHIGHLIGHTSAs a special branch of metamaterials characterized by phase discontinuity, elastic metasurfaces have presented extraordinary capacity for elastic wave manipulation. This class of metamaterials has received extensive attention in recent years. In this paper, a subwavelength elastic metasurface with locally resonant prisms is employed to steer the propagation of the A0 Lamb wave. Based on the dispersion curve and transmission ratio, we establish that the resonant feature of prisms is influenced by the diagonal ratio of cross section. By gradually tuning the diagonal ratio of prism cross section, the pattern of resonance modes and the mechanism of resonance superposition are clarified. In this regard, two different resonant modes can be superimposed at a certain frequency. A complete 2π phase shift that is crucial for redirecting wave propagation can therefore be realized. To have a broader working frequency range, the influence of prism height on the resonance superposed frequency and the effect of plate thickness on the incident flexural wave are explored. Based on the generalized Snell’s law, negative refraction is verified numerically through a metasurface assembled from unit cells with constant phase change. In addition, other wavefront modulations such as eccentric focusing, nonparaxial propagation are also demonstrated. This novel design introduces new degrees of freedom in many engineering applications such as seismic wave protection, structural health monitoring and energy harvesting.Proposing a novel subwavelength prismatic metasurface at mm-scale capable of operating in the kHz frequency range.Introducing an approach for altering the resonant mode frequency of building block.Establishing mechanism of resonant mode frequency variation and superposition.Realizing full phase span from 0 to 2π by superimposing of compression and bending modes.Demonstrating abnormal wavefront control for flexural wave by novel prismatic metasurfaces, such as negative refraction, eccentric focusing, parabolic and curvilinear wave trajectories. [ABSTRACT FROM AUTHOR]

In order to achieve low frequency vibration and noise reduction, researchers have found and explored many types of metamaterial structures. Based on this, an innovative multiphase metamaterial structure composed of hard materials and soft materials is proposed in this paper. According to Bloch's theorem, the band gap characteristics of the proposed structure are calculated using the finite element method, and the formation mechanism of the band gap is analyzed. In addition, the effects of the stiffness and density of the two materials on the band gap are studied in detail. Then, the phase velocity, group velocity and wave propagation direction are calculated according to a certain frequency of the specific dispersion curve, and the important information of wave propagation in the structure is obtained. Finally, according to the transmission characteristics of vibration in a finite periodic structure, it is verified that the existence of band gap can inhibit the vibration transmission, and it is further clarified that the proposed structure has a good performance in the design of low-frequency band gaps with large amplitude. [ABSTRACT FROM AUTHOR]

This article extends recently developed finite variation sensitivity analysis (FVSA) approaches to an inverse homogenization problem. The design of metamaterials with prescribed mechanical properties is stated as a discrete density‐based topology optimization problem, in which the design variables define the microstructure of the periodic base cell. The FVSA consists in estimating the finite variations of the objective and constraint functions after independently switching the state of each variable. It is used to properly linearize the functions of binary variables so the optimization problem can be solved through sequential integer linear programming. Novel sensitivity expressions were developed and it was shown that they are more accurate than the ones conventionally used in literature. Referred to as the conjugate gradient sensitivity (CGS) approach, the proposed strategy was quantitatively evaluated through numerical examples. In these examples, metamaterials with prescribed homogenized Poisson's ratios and minimal homogenized Young's moduli were obtained. A hexagonal base cell with dihedral D3$$ {D}_3 $$ symmetry was used to produce only metamaterials with isotropic properties. It was shown that, by using the CGS approach instead of the conventional sensitivity analysis, the sensitivity error was substantially reduced for the considered problem. The proposed developments effectively improved the stability and robustness of the discrete optimization procedures. In all the considered examples, when more accurate sensitivity analyses were performed, the parameters of the topology optimization method could be tuned more easily, yielding effective solutions even if the settings were not ideal. [ABSTRACT FROM AUTHOR]

AbstractThis paper proposes a UAV wing based on smart metamaterial resonators (smart meta-wing), and studies its vibration wave attenuation under aerodynamic loads. A novel aeroelastic transfer matrix, incorporating aerodynamic effects, is developed to analyze the wave propagation. The study examines the influence of smart resonators on the coupled flexural-torsional wave attenuation with and without aerodynamic effects. The findings reveal that a new bandgap (aeroelastic bandgap) is formed along with local bandgap (SR bandgap), effectively attenuating both flexural and torsional waves. Additionally, the bandgap behavior can be actively tuned by varying the control gain of smart resonators. The proposed smart meta-wing model and aeroelastic transfer matrix offer a novel approach for actively attenuating the aeroelastic vibration waves of UAV wings for desired frequency range. [ABSTRACT FROM AUTHOR]

This paper presents the design and analysis of a metamaterial-based wideband microwave absorber in the C- and X-band, comprised of lumped resistors, having thicknesses of the order of 0.05 λ mm. The structure was micro-machined on the FR-4 sheet in a periodically arranged array of 15 × 15 unit cells. These unit cells have a dimension of 12 × 12 mm each. The proposed absorber design presents excellent broadband absorption characteristics with relative bandwidth (RBW) of 85.05% covering a bandwidth of 8.02 GHz ranging from 5.42 to 13.44 GHz. The absorption mechanism has been explained with the help of characteristic impedance and surface current densities in the operating region. The designed absorber shows polarization angle independency and wide incidence angle stability for the incident microwaves. The results of the prototype are compared with the simulated results illustrating excellent compatibility with the simulation results. Absorber structure may find its potential use in camouflage applications during war times. [ABSTRACT FROM AUTHOR]

This article presents a symmetrical reduced-size eight-element MIMO antenna array with high electromagnetic isolation among radiators. The array utilizes easy-to-build techniques to cover the n77 and n78 new radio (NR) bands. It is based on an octagonal double-negative metamaterial split-ring resonator (SRR), which enables a size reduction of over 50% for the radiators compared to a conventional disc monopole antenna by increasing the slow-wave factor. Additionally, due to the extreme proximity between the radiating elements in the array, the modal significance (MS) method was employed to identify which propagation modes had the most impact on the electromagnetic coupling among elements. This approach aimed to mitigate their effect by using an electromagnetic barrier, thereby enhancing electromagnetic isolation. The electromagnetic barriers, implemented with strip lines, achieved isolation values exceeding 20 dB for adjacent elements (<0.023 λ) and approaching 40 dB for opposite ones (<0.23 λ) after analyzing the surface current distribution by the MS method. The elements are arranged in axial symmetry, forming an octagon with each antenna port located on a side. The array occupies an area of 0.32 λ2 at 3.5 GHz, significantly smaller than previously published works. It exhibits excellent performance for MIMO applications, demonstrating an envelope correlation coefficient (ECC) below 0.0001, a total active reflection coefficient (TARC) lower than −10 dB for various incoming signals with random phases, and a diversity gain (DG) close to 20 dB. [ABSTRACT FROM AUTHOR]

The suppression of low-frequency vibration and noise has always been an important issue in a wide range of engineering applications. To address this concern, a novel square hierarchical honeycomb metamaterial capable of reducing low-frequency noise has been developed. By combining Bloch's theorem with the finite element method, the band structure is calculated. Numerical results indicate that this metamaterial can produce multiple low-frequency bandgaps within 500 Hz, with a bandgap ratio exceeding 50%. The first bandgap spans from 169.57 Hz to 216.42 Hz. To reveal the formation mechanism of the bandgap, a vibrational mode analysis is performed. Numerical analysis demonstrates that the bandgap is attributed to the suppression of elastic wave propagation by the vibrations of the structure's two protruding corners and overall expansion vibrations. Additionally, detailed parametric analyses are conducted to investigate the effect of θ, i.e., the angle between the protruding corner of the structure and the horizontal direction, on the band structures and the total effective bandgap width. It is found that reducing θ is conducive to obtaining lower frequency bandgaps. The propagation characteristics of elastic waves in the structure are explored by the group velocity, phase velocity, and wave propagation direction. Finally, the transmission characteristics of a finite periodic structure are investigated experimentally. The results indicate significant acceleration amplitude attenuation within the bandgap range, confirming the structure's excellent low-frequency vibration suppression capability. [ABSTRACT FROM AUTHOR]

Designing and fabricating a directional coupler with composite right/left-hand (CRLH) transmission lines with a coupling level of 15 dB is presented in this paper. Compared to conventional couplers, this asymmetric structure has achieved this coupling level compared to the simple transmission line. This structure is comprised of interdigital capacitors and short connection stubs. The distance between two coupled lines is equal to 0.4 mm, and the stubs are spirally designed to compress the structure. The subs' length is approximately equal to λ/4, and the impedance of the ports is equal to 50 Ω. After designing and simulating, the coupler was fabricated and measured. The directional coupler at the frequency of 1.9 GHz has an isolation level of 44 dB and a directivity of 67.1 dB. Overall, construction and simulation results are in good agreement. [ABSTRACT FROM AUTHOR]

In this paper, a ferrite-filled rectangular waveguide as a balanced composite right/left-handed (CRLH) transmission line is considered. Based on the surface current density of dominant mode, a centerline longitudinal slot on the broad wall of this ferrite-filled rectangular waveguide can be radiate to the free space as a leaky-wave antenna (LWA). This proposed LWA has the both capability of the fixed-bias frequency scanning and fixed-frequency bias scanning from negative to positive angles. However, the gain of the centerline slotted ferrite-filled rectangular waveguide antenna is not acceptable. By adding another slot and changing the position of slots on the broad wall, the gain is improved to more than 9 dB in frequency range of 6.59–6.69 GHz. [ABSTRACT FROM AUTHOR]

This paper intends to provide an application example of using metamaterials for elastic wave manipulation inside a nonlinear waveguide. The concept of phase-gradient metasurfaces, in the form of artificially architectured structures/materials, is adopted in nonlinear-guided-wave-based structural health monitoring (SHM) systems. Specifically, the second harmonic lowest-order antisymmetric Lamb waves (2nd A0 waves), generated by the mutual interaction between primary symmetric (S) mode and antisymmetric (A) mode waves, show great promise for local incipient damage monitoring. However, the mixing strength is adversely affected by the wave beam divergence, which compromises the 2nd A0 wave generation, especially in the far field. To tackle this problem, a metasurface is designed to tactically enhance the 2nd A0 waves through manipulating the phases and amplitudes of both primary waves simultaneously. After theoretically revealing the features of the 2nd A0 wave generation in a weakly nonlinear plate, an inverse-design strategy based on topology optimization is employed to tailor-make the phase gradient while ensuring the high transmission of the primary waves, thus converting the diverging cylindrical waves into quasi-plane waves. The efficacy of the design is tested in a 2nd-A0-wave-based SHM system for material degradation monitoring. Results confirm that the manipulated S and A mode waves can propagate in a quasi-planar waveform after passing the surface-mounted metasurface. Changes in material properties inside a local region of the host plate can be sensitively captured through examining the variation of the 2nd A0 wave amplitude. The concept presented here not only showcases the potential of metamaterial-enhanced 2nd A0 waves for material degradation monitoring, but also illuminates the promising direction of metamaterial-aided SHM applications in nonlinear waveguides. [ABSTRACT FROM AUTHOR]

Metasurfaces are opening promising flexibilities to reshape the wavefront of electromagnetic waves. Notable optical phenomena are observed with the tailored surface plasmon, which is excited by metallic components in the visible spectrum. However, metamaterial or metasurface devices utilizing metallic materials encounter the challenge of low transmission efficiency, particularly within the visible spectrum. This study proposes a multilayer design strategy to enhance their transmission efficiency. By incorporating additional metal layers for improvements in the transmission efficiency and dielectric layers as spacers, cavities are formed along the propagation direction, enabling the modulation of transmittance and reflection through a process mimicking destructive interference. An analytical model simplified with the assumption of deep-subwavelength-thick metal layers is proposed to predict the structural parameters with optimized transmittance. Numerical studies employing the rigorous coupled wave analysis method confirmed that the additional metal layers significantly improve the transmittance. The introduction of the extra metal and dielectric layers enhances the transmission efficiency in specific spectral regions, maintaining a controllable passband and transmittance. The results indicate that the precise control over the layers' thicknesses facilitates the modulation of peak-to-valley ratios and the creation of comb-like filters, which can be further refined through controlled random variation in the thickness. Furthermore, when the thickness of the silver layer followed an arithmetic sequence, a multilayer structure with a transmittance of approximately 80% covering the entire visible spectrum could be achieved. Significantly, the polarization extinction ratio and the phase delay of the incident beams could still be modulated by adjusting the geometrical structure and parameters of the multilayer metamaterial for diversified functionalities. [ABSTRACT FROM AUTHOR]

Infrared metamaterial absorbers underpin many entrenched scientific and technical applications, including radiative cooling, energy harvesting, infrared detectors, and microbolometers. However, achieving both perfect and ultra-broadband absorption remains an unmet scientific challenge because the traditional metamaterial absorber strategy suffers from complex multi-sized resonators and multiple meta-element patterns. We demonstrate a simple ultra-broadband infrared metamaterial absorber consisting of tilted graphite wires and an Al reflector. The proposed tilted wires-based metamaterial (TWM) absorber exhibits absorption of above 0.95 across the middle to very long-wavelength infrared spectrum (3–30 µm). By increasing the aspect ratio, the bandwidth can be expanded and achieve near-perfect absorption in the 3–50 μm spectral range. The excellent infrared absorptance performance primarily originates from the ohmic loss induced by the electromagnetic coupling between neighboring tilted wires. Furthermore, we propose a typical three-layer equivalent model featuring a resonator/insulator/reflector configuration that requires more than 84 resonant cavities to obtain comparable infrared absorptance. Our high-performance TWM absorber could accelerate the development of next-generation infrared thermal emitters and devices and other technologies that require infrared absorption. [ABSTRACT FROM AUTHOR]

This paper addresses the limited gain of conventional Antipodal Vivaldi Antenna (AVA) at higher frequencies. We propose a novel Metamaterial Lens Vivaldi Antenna (MLVA) design that overcomes this limitation by integrating an exponentially tapered antenna lens and a strategically placed Near Zero Refractive Index (NRZI) metamaterial lattice. The MLVA achieves exceptional wideband performance with a −3 dB gain bandwidth exceeding 148.6% from 3.7 to 25 GHz. The result demonstrates a peak realized gain of 11.8 dBi at 11.2 GHz, compared to 9.1 dBi conventional AVA, especially beyond 5 GHz. The compact MLVA design measures only 120 × 78 × 1.524 mm3 (1.48 × 0.96 × 0.0188λ03) λ0 where free‐space wavelength is the lowest frequency and is fabricated on RO4350 B substrate with a 50‐Ω SMA connector. Key features of the design include exponential flaring, and trapezoidal lens geometries chosen for their inherent ability to effectively collimate and direct the spherical wavefront. The incorporation of a dielectric lens and metasurface further enhances gain and Front‐to‐Back Ratio (FBR) by directing the majority of energy in the end‐fire direction. Experimental results validate the effectiveness of the proposed design, confirming simulation predictions. These outstanding characteristics make the MLVA a promising candidate for diverse wireless communication and radar applications demanding high data rates across a broad frequency range. Plain Language Summary: This paper introduces a new type of antenna called the Metamaterial Lens Vivaldi Antenna (MLVA), designed to perform better at high frequencies than conventional Antipodal Vivaldi Antenna (AVA). By incorporating a special lens and innovative materials, the MLVA achieves a wide range of frequencies from 3.7 to 25 GHz and a high gain of 11.8 dBi at 11.2 GHz. The compact design (measuring 120 × 78 × 1.524 mm3 or 1.48 × 0.96 × 0.0188λ03) has been validated through simulations and real‐world tests. These improvements make the MLVA ideal for high‐speed wireless communication and radar systems. Key Points: The Metamaterial Lens Vivaldi Antennas (MLVA) offer higher gain and broader bandwidth than conventional Antipodal Vivaldi AntennasThe design uses an exponentially tapered lens and NRZI metamaterial lattice to enhance high‐frequency performanceThe compact MLVA, validated by simulations and experiments, is ideal for high‐data‐rate wireless communication and radar applications [ABSTRACT FROM AUTHOR]

The shift to higher orbits requires larger space structures that are assembled on-orbit. These large space structures experience problematic vibrations at low frequencies, especially during robotic assembly in space. Beyond active vibration control, which is expensive and often infeasible, current passive mitigation strategies are limited. Here, struts of the space frame are transformed to resonant metamaterials via periodically placed resonators along their length, providing a pathway for energy exhaustion. Simple and multi-degree of freedom resonators were successfully applied to struts to mitigate vibrations of frequencies <500 Hz. In frames, a dependence on resonator layout relative to the excitation point is demonstrated. [ABSTRACT FROM AUTHOR]

Metasurfaces can replace bulk optical components in a more compact form factor in applications including communication systems, sensors, and manufacturing technology. However, their design and fabrication is challenging due to competing demands of selecting meta-atoms that simultaneously provide the required amplitude and phase modulation while being robust to fabrication errors. Here, we develop two design heuristics to assist with the down-selection of meta-atoms into sensitivity-informed libraries, based on either selecting meta-atoms with minimal sensitivity or minimizing the relative sensitivities between meta-atoms. We evaluate both methods on a polarization-dependent phase mask and compare the resulting phase and intensity errors. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A new high gain MIMO array antenna with limited side lobe level between 27.5 and 28.5 GHz is modeled for 5G WLAN applications. The modeled configuration involves two-port MIMO with 8-element array antenna printed on a Rogers RT Duroid-5880 dielectric material. To enhance the antenna’s radiation characteristics, each element in the radiator is excited using corporate inset feeding. The proposed model operates well in the bandwidth of 27.5 to 28.5 GHz, resonating at 28 GHz with a return loss of − 40 dB. For an array configuration, the proposed MIMO array radiator exhibits better limited side lobe level of − 7 dBi (left) and − 4 dBi (right). The MIMO array antenna with a total footprint of 123 × 61 × 0.8 mm3 offers 14 dBi gain in the operating bandwidth. Since the model is configured to be a MIMO antenna, the MIMO attributes such as isolation, TARC, diversity gain, and correlation parameters are analyzed and estimated to be around − 17.25 dB, − 24 dB, 10 dB, and 0.006, respectively, over the band of interest. The proposed model is fabricated and experimentally validated for its simulation results and is found to be in good agreement with simulation results. [ABSTRACT FROM AUTHOR]

The present study focuses on the use of waste materials to generate cost-effective microwave absorption composites. Rice husk (agricultural waste) and exhausted activated charcoal (water filter cartridge waste) were used as waste materials for microwave absorption. Both were blended in different proportions using a planetary ball mill to prepare samples. The XRF and particle size studies were carried out for element and particle size analysis, and for dielectric properties measurement, a vector network analyzer was used. The findings reveal the microwave absorption in the frequency range of 2 to 18 GHz by the blended composites. Sample RHC-11 with 20% exhausted activated charcoal showed a maximum reflection loss of − 38.3 dB at 12 GHz. For further improvement in microwave absorption, the dielectric characteristics of the composites were utilized to develop a layered metamaterial-based microwave absorber. The layered metamaterial is a unique and simple patch design that displays good microwave absorption > 90% and absorbs 99.34% of microwave energy at 16 GHz frequency. The developed metamaterial-based microwave absorber shows an absorption bandwidth of 6.60 GHz with a thickness of 2.3 mm. In addition, the proposed structure is independent of the oblique incidence angle and polarization angle. [ABSTRACT FROM AUTHOR]

The development of a semiconductor adjustable absorber in the THz will open up new possibilities for quantum information science, imaging, health, and sensing applications, particularly those that need to be portable. Here, we build a unique semiconductor nanowire metamaterial that exhibit increased absorption efficiency at various temperatures by carefully organizing and shaping the semiconductor nanowire array. This discovery paves the way for the potential development of a new generation of THz quantum detectors that operate close to room temperature and offer exceptional improved absorption for a broader variety of applications. [ABSTRACT FROM AUTHOR]

A metamaterial-based non-uniform dipole array antenna is presented for high gain 5G millimeter-wave applications with a wideband characteristic. Initially, a non-uniform dipole array is designed on a 0.202 mm thick Rogers RO4003C substrate, offering a wide operating bandwidth ranging from 23.1 GHz to 44.8 GHz. The dipole array antenna emits unidirectional end-fire radiation with a maximum gain of 8.1 dBi and an average gain of 6.7 dBi. Subsequently, to achieve high gain performance, a 5 × 7 metamaterial structure is designed in the direction of the antenna radiation. The implemented metamaterial structure is optimized for the operating frequency, enhancing the directivity of the antenna radiation and resulting in a gain increment of more than 3 dBi compared to the dipole array alone. The developed metamaterial-integrated dipole array antenna offers an operating bandwidth (S11 < −10 dB) of more than 21 GHz (63.92%), ranging from 23.1 GHz to 44.8 GHz, covering the most commonly used 5G millimeter-wave frequency bands (n257, n258, n259, n260, and n261). Furthermore, the presented antenna yields a stable high gain with a peak gain of 11.21 dBi and a good radiation efficiency of more than 64%. The proposed antenna is an excellent option for millimeter-wave 5G systems due to its overall properties, particularly its high gain and end-fire radiation characteristics, combined with a wide operating bandwidth. [ABSTRACT FROM AUTHOR]

In this study, we achieved energy localization and amplification of flexural vibrations by utilizing the defect mode of plate-attachable locally resonant metamaterials, thereby realizing compact and low-frequency vibration energy suppression and energy harvesting with enhanced output performance. We designed a cantilever-based metamaterial unit cell to induce local resonance inside a periodic supercell structure and form a bandgap within the targeted low-frequency range of 300–450 Hz. Subsequently, a defect area was created by removing some unit cells to break the periodicity inside the metamaterial, which led to the isolation and localization of the vibration energy. This localized vibration energy was simultaneously converted into electrical energy by a piezoelectric energy harvester coupled with a metamaterial inside the defect area. Consequently, a substantially enhanced energy harvesting output power was achieved at 360 Hz, which was 43-times higher than that of a bare plate without metamaterials. The proposed local resonant metamaterial offers a useful and multifunctional platform with the capability of vibration energy isolation and harvesting, while exhibiting easy handling via attachable designs that can be tailored in the low-frequency regime. Highlights: • Compact multifunctional vibration isolation-energy harvesting metastructures based on a low-frequency defect bandgap. • Enhanced harvesting power by a factor of 43 over a wide frequency range of 310-380 Hz • Easily mass-produced metamaterial unit cell via a laser-cutting process. • Multifunctionality, i.e., vibration isolation and harvesting, proved by a carefully-designed experiment. [ABSTRACT FROM AUTHOR]

Directional sources like the Huygens source enable electromagnetic wavefront forming/shaping with great flexibility and have made impacts in photonics, applied physics, metasurfaces, and antenna engineering. The related Janus source features a strongly directional near‐field and a quasi‐isotropic far‐field, which gives it promising application potentials distinct from, and complementary to, the Huygens source. Nevertheless, most existing Janus sources face strong limitations in efficiency and/or 3D operation, hindering their practical application. This paper introduces a 3D active Janus source that achieves near‐field directionality over a wide bandwidth and a power efficiency much improved over existing passive Janus sources. It is shown that a class of quasi‐isotropic antennas are actually active Janus sources (which is referred to as the Janus antenna). A well‐designed Janus antenna is demonstrated which (a) exhibits near‐field directionality over a broad bandwidth of 28.9%, and (b) in a practical usage environment, achieves a power efficiency ≈60 times higher than a passive Janus source. This work elucidates the connection between the “Janus dipole” concept in physics and the “quasi‐isotropic antenna” concept in antenna design, and paves the way for the design of future directional devices with much improved bandwidth and efficiency. [ABSTRACT FROM AUTHOR]

The concept of metamaterial recently emerged as a new frontier of scientific research, encompassing physics, materials science and engineering. In a broad sense, a metamaterial indicates an engineered material with exotic properties not found in nature, obtained by appropriate architecture either at macro-scale or at micro-/nano-scales. The architecture of metamaterials can be tailored to open unforeseen opportunities for mechanical and acoustic applications, as demonstrated by an impressive and increasing number of studies. Building on this knowledge, this theme issue aims to gather cutting-edge theoretical, computational and experimental studies on elastic and acoustic metamaterials, with the purpose of offering a wide perspective on recent achievements and future challenges. This article is part of the theme issue, 'Current developments in elastic and acoustic metamaterials science (Part 2)'. [ABSTRACT FROM AUTHOR]

Structural lattices with quasi-periodic patterns possess interesting dynamic features that can be exploited to control, localize and redirect propagating waves. In this work, we show that the properties of a large class of quasi-periodic locally resonant systems (approximated as periodic, with arbitrarily large period) can be performed by defining an equivalent discrete system. Several properties of wave propagation can a priori be demonstrated with reference to this system. Results in terms of bulk spectrum, showing the Hofstadter butterfly pattern, and of topological modes are then discussed in detail with reference to a simple example of quasi-periodic lattice. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 2)'. [ABSTRACT FROM AUTHOR]

Three-dimensional metamaterials endowed with two-dimensional in-plane periodicity exhibit peculiar thermoelastic behaviour when heated or cooled. By proper design of the unit cell, the equivalent thermal expansion coefficient can be programmed and can also reach negative values. The heterogeneity in the third direction of such metamaterials also causes, in general, a thermal-induced deflection. The prediction of the equivalent thermal properties is important to design the metamaterial suitable for a specific application. Under the hypothesis of small thickness with respect to the global in-plane dimensions, we make use of asymptotic homogenization to describe the thermoelastic behaviour of these metamaterials as that of an equivalent homogenous plate. The method provides explicit expressions for the effective thermal properties, which allow for a cost-effective prediction of the thermoelastic response of these metaplates. [ABSTRACT FROM AUTHOR]

In this article, we present the design and experimental validation of a labyrinthine metamaterial for vibro-acoustic applications. Based on a two-dimensional unit cell, different designs of finite-size metamaterial specimens in a sandwich configuration including two plates are proposed. The design phase includes an optimization based on Bloch-Floquet analysis with the aims of maximizing the band gap and extruding the specimens in the third dimension while keeping the absorption properties almost unaffected. By manufacturing and experimentally testing finite-sized specimens, we assess their capacity to mitigate vibrations in vibro-impact tests. The experiments confirm a band gap in the low- to mid-frequency range. Numerical models are employed to validate the experiments and to examine additional vibro-acoustic load cases. The metamaterial's performances are compared with benchmark solutions, usually employed for noise and vibration mitigation, showing a comparable efficacy in the band gap region. To eventually improve the metamaterial's performance, we optimize its interaction with the air and test different types of connections between the metamaterial and the homogeneous plates. This finally leads to metamaterial samples largely exceeding the benchmark performances in the band gap region and reveals the potential of interfaces for performance optimization of composed structures. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'. [ABSTRACT FROM AUTHOR]

Many deployable structures in nature, as well as human-made mechanisms, preserve symmetry as their configurations evolve. Examples in nature include blooming flowers, dilation of the iris within the human eye, viral capsid maturation and molecular and bacterial motors. Engineered examples include opening umbrellas, elongating scissor jacks, variable apertures in cameras, expanding Hoberman spheres and some kinds of morphing origami structures. In these cases, the structures either preserve a discrete symmetry group or are described as an evolution from one discrete symmetry group to another of the same type as the structure deploys. Likewise, elastic metamaterials built from lattice structures can also preserve symmetry type while passively deforming and changing lattice parameters. A mathematical formulation of such transitions/deployments is articulated here. It is shown that if X is Euclidean space, G is a continuous group of motions of Euclidean space and Γ is the type of the discrete subgroup of G describing the symmetries of the deploying structure, then the symmetry of the evolving structure can be described by time-dependent subgroups of G of the form Γαt:=αtΓαt−1 , where αt is a time-dependent affine transformation. Then, instead of considering the whole structure in X , a 'sector' of it that lives in the orbit space Γαt\X can be considered at each instant in time, and instead of considering all motions in G , only representatives from right cosets in the space Γαt\G need to be considered. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'. [ABSTRACT FROM AUTHOR]

Here, we propose a sensing scheme based on an all-dielectric metamaterial with the smooth reflection and transmission spectral lines in 10-60THz, and verify the applications of the measuring the resonance characteristics of Xuan paper samples. The reflection and thermal conductivity of Xuan paper samples enhance with the concentration of alum water increasing and weaken due to the thickness increasing. These results provide a solid foundation for this metamaterials in measuring the reflective and thermal resonance properties of Xuan paper samples. [ABSTRACT FROM AUTHOR]

Lattice structures with customizable acoustical and mechanical properties show significant promise as practical engineering materials. However, the geometry of traditional lattice structures simultaneously dictates both acoustical and mechanical properties, with alterations in one impacting the other, leaving little room for customization. Herein, leveraging the mechanism of Helmholtz resonators, a general recipe is presented to independently introduce sound absorption and mechanical properties in lattice structures. The sound absorption component is based on a perforated plate, while the mechanical component is based on a truss structure. Through a high‐fidelity analytical acoustics model is developed, and finite element analysis outlines the range of properties achievable through the proposed structures. The design encompasses structures with effective absorption, characterized by a resonance peak with coefficient ≥0.7, across almost every frequency in a broad range from 1000 to 5000 Hz, within a range of lattice thicknesses from 21 to 25.5 mm. Also, diverse range of stiffness and strength, and large‐strain deformation modes, can be achieved through the implementation of different trusses. Finally, the concept is validated experimentally through 3D‐printed samples. This innovative approach allows for the tailored creation of lattice structures that specifically address the acoustical and mechanical requirements in diverse applications. [ABSTRACT FROM AUTHOR]

The paper presents a metamaterial with reconfigurable effective properties, intended to operate in alternating magnetic fields. The structure of a resonator, based on a series connection of a planar inductor and a lumped capacitor, is expanded using an additional capacitor with a MOSFET transistor. Due to the presence of the controllable active element, it is possible to dynamically change the phase of the current flowing through a meta-cell and shift a frequency response within an assumed range. Since the transistor is driven by the unipolar square wave with a changeable duty cycle and time delay, two closed-loop controllers were utilized to achieve a smart material, able to automatically attain and maintain the imposed resonant frequency. As a result, the complex effective magnetic permeability of the metamaterial can be smoothly changed, during its operation, via an electrical signal, i.e. by adjusting the parameters of a control signal of the active element. The design of the meta-cell, as well as the measuring, data operation and control part, are presented in detail. An illustrative system is examined in terms of achieving the user-defined resonance point of the metamaterial. Transient responses with estimated settling times and steady-state errors and the effective permeability characteristics for the exemplary cases are shown. The meta-cell is also tested experimentally to validate the theoretically determined effective properties. [ABSTRACT FROM AUTHOR]

In recent years, thermal imaging and sensing technologies have seen dramatic increases in usage for a range of applications. However, the material cost and manufacturing complexity of infrared optics remain a major barrier toward their democratization. Here, a solution‐processed plasmonic reflective filter (PRF) is presented as a scalable, disordered, and low‐cost thermal infrared (TIR) optic. The PRF selectively absorbs sunlight and specularly reflects TIR wavelengths, with a performance comparable to state‐of‐the‐art infrared optics made of materials like Germanium. Unlike the latter, however, the PRF is fabricated using low‐cost materials and a "dip‐and‐dry" chemical synthesis technique, which enables orders of magnitude lower manufacturing costs. The PRF's optical functionality and integration into infrared imaging systems are experimentally demonstrated. The chemical synthesis technique also affords exceptional spectral tuneability and material compatibility compared to traditional fabrication methods. The PRF's tuneable and broadband TIR yield can be augmented by inexpensive dielectric or polymeric filters to yield novel capabilities such as wide‐area ambient temperature surveys. Practically, the PRF represents a significant advance toward democratizing the benefits of thermal imaging and sensing. Scientifically, it represents a previously unexplored optical functionality of disordered materials, and a new direction for versatile chemical synthesis in designing optical components. [ABSTRACT FROM AUTHOR]

A new, high‐gain, high‐efficiency, long‐range passive metamaterial UHF‐RFID tag is proposed. Measuring 16.1 × 8.1 × 1.6 cm, it integrates a modified taper‐shaped dipole antenna with the NXP UCODE 8 chip and an artificial magnetic conductor (AMC) structure shaped like a double open‐end wrench. This cost‐effective tag achieves read ranges comparable to those of battery‐assisted passive (BAP) tags, up to 64.7 m in a shipping container at 918 MHz and 56.7 m in free space at 928 MHz. Theoretical analysis shows moderate agreement with experimental validation in an anechoic chamber and outdoors. The proposed tag addresses challenging scenarios, enabling previously unattainable passive RFID applications. It supports vessel detection in maritime environments, with potential uses in automated access control at bridges, gates, and locks in smart waterways and premier marinas. It also supports multivehicle detection, allowing applications, such as streamlining emergency services and smart city traffic management. Furthermore, its capability extends to smart hangar applications, such as automatic updates to pilots' electronic logbooks and aircraft supervision. [ABSTRACT FROM AUTHOR]

Architected materials exhibit unique properties and functionalities based on the geometric arrangement of their constituent materials. In most cases, these parameters are fixed, requiring that the system be redesigned and reconstructed if different properties are desired. Both stimuli‐responsive materials and modular designs have been used to enable re‐programmable properties in the past, but often have limitations, such as the need for a continuous application of external stimuli or power, or unwanted global morphing. In this study, a locally stable anti‐tetra chiral (LSAT) metamaterial is introduced consisting of independently multistable units that can deform and change state without inducing changes in the global morphology. Adjacent cells are only weakly coupled, allowing the collective metamaterial to be switched between many different possible states. Local bistability enables re‐programmable heterogeneity, such as the snapping of cells along an edge or diagonally within the architected material. Utilizing finite element analysis (FEA), the influence of key geometric parameters on the re‐programmability of the metamaterials is systematically investigated. The effect of these parameters on properties such as shear stiffness, Poisson's ratio, and vibration are also investigated using experimental prototypes. This re‐programmable metamaterial promises to expand the design space for mechanical systems, with potential applications in non‐traditional computation, robotic actuation, and adaptive structures. [ABSTRACT FROM AUTHOR]

Inspired by the differences in the barbed structures of some plant stems and cat tongues in different directions, a reusable and easy-to-recover barbed metamaterial was designed, with its mechanical properties analyzed theoretically and numerically. The results show that, in the reciprocating motion of the barbs, when the barb rectangular section sizes are 1 mm × 1 mm, the length is 20 mm, and the angle with the vertical direction is 60°, the maximum reaction force in the forward contact process with the blocking rib will be about 20 times of the maximum reaction force in the reverse contact process, and the former energy consumption is about 200 times of the latter. With the decrease of the angle between the barb and the vertical direction, the barb structure will exhibit a higher energy absorption capacity and a reduced energy requirement for recovery. Similarly, with the increase of the barb length, the structure energy absorption will be lower and the energy required for recovery will reduce. These characteristics indicate that, the structure possesses excellent impact resistance and energy absorption capacity. Structures with significant energy disparities between forward and backward motions are more easily recoverable, and the energy absorption efficiency can be enhanced by carefully designing the angles and lengths of the barbs. [ABSTRACT FROM AUTHOR]

Graphene-based metamaterial absorbers are increasingly popular for developing various reconfigurable and electrically tunable optical devices, especially in the terahertz (THz) range. This paper aims to design a broadband THz metamaterial absorber (MMA) based on graphene. The proposed absorber consists of a patterned graphene surface layer, a dielectric layer, and a bottom metallic film. The patterned graphene surface layer is composed of two parts with different slots to induce multiple plasmonic resonances. CST simulation results show that the bandwidth with an absorption efficiency exceeding 95% is 3.12 THz, ranging from 4.01 to 7.13 THz. We validated the simulation results using multi-reflection interference theory. To explore the physical mechanisms of broadband absorption, the distribution of the surface electric field in the structure was studied. We also found that the absorber exhibits polarization insensitivity and wide-angle incidence characteristics. The absorption frequency of the absorber can be tuned by changing the chemical potential of graphene. Some notable features of the proposed absorber include the maximum bandwidth and minimal unit cell size of a single-layer absorber without sacrificing polarization insensitivity or amplitude tunability. Besides, the absorber has a thickness of 7.2 μm and a unit cell period of 4 μm, thus its structure is very compact in comparison with most previous MMAs. This proposed MMA has potential applications in terahertz detection, filtering, imaging and stealth technology. [ABSTRACT FROM AUTHOR]

This paper investigates the potential of a transition metal nitride, Vanadium Nitride (VN), in designing a nanostructured absorber for infrared wavelengths. A simple and plain nano circular ring composed of VN is printed over a metal-backed lossy substrate to implement broadband absorber. The proposed VN-based absorber offers an exceptional absorption characteristic across the large operating wavelength from 1000 to 2400 nm with an absorption threshold of 90%. The absorption properties of this VN absorber have also been analyzed by varying the oblique angles of the optical light and it exhibits a good absorption value of more than 70% even at θ = 60°. Due to the symmetry in the nano-ring of VN, it also achieves the polarization-insensitive response by varying the rotation angles (polarization angles). Moreover, the multi-reflection interference theory has been introduced to verify the simulation results of the proposed VN-absorber. Because of its thermal robustness, mechanical stability, and wide absorption bandwidth, it holds promise for applications in solar cells and thermophotovoltaics. [ABSTRACT FROM AUTHOR]

The polygonal honeycomb core has been vertically rotated and spliced to form a new three-dimensional polygonal honeycomb (TPH) structure lattice. Young's modulus and Poisson's ratio for the three main directions of the TPH structure had been derived from Castigliano's second theorem and Moore's theorem. The theoretical results show good agreement with the numerical and experimental results. Meanwhile, the compressive strength of the TPH structure has been analyzed. The results show that the geometric parameters have a significant effect on the elasticity and strength of TPH structures, and the mechanical properties of the TPH structures can be programmed by adjusting the geometric parameters. In addition, the TPH structure exhibits a bidirectional zero Poisson's ratio (ZPR) during compression. This structure shows promise for applications in aerospace, construction, and other fields. This study provides guidance for further research on polygonal honeycomb structures. [ABSTRACT FROM AUTHOR]

The combination of 3D printing, polymer derived ceramics, and electromagnetic wave (EMW) absorption metamaterials is particularly useful for spacecraft stealth in extreme environments and is gradually gaining significant interest. While the 3D printing of SiOC has been extensively researched, the high temperature stability and mechanical performance of SiOC are not as favorable as SiCN. However, it remains challenging to prepare SiCN metamaterials with both high mechanical and microwave absorption properties by 3D printing. Herein, we demonstrate a SiCN EMW absorption metamaterial with high mechanical properties using digital light processing 3D printing, which achieves a minimum reflection loss of −31.01 dB (99.9 % absorption), and the widest effective absorption bandwidth covers the entire X-band from 8.2 to 12.4 GHz. And the EMW absorption performance can be adjusted based on the size of the unit structure. [ABSTRACT FROM AUTHOR]

Simulations and experiments were conducted to control the shock‐to‐detonation transition by energy trapping in localized regions of nitromethane that contained arrays of embedded dense particles (tantalum rods). The localizations were additively manufactured and designed with simulations carried out with ALE3D, that used the ignition and growth reactive flow model for the explosive. Modelling demonstrated enhanced reactivity when the tantalum rods were present, leading to a detonation that otherwise did not occur for the same strength shock without rods. Experiments that confirmed predictions of the simulation were conducted using Fritz plane wave lenses to drive various input shocks into the system. Photon doppler velocimetry was the primary diagnostic used to measure shock input and reaction progression. These results suggest that it is possible design explosives to localize sensitivity to shock loading within an insensitive material increasing the overall safety of fielded energetic materials. [ABSTRACT FROM AUTHOR]