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3-3 Piezoelectric Metamaterial with Negative and Zero Poisson’s Ratio for Hydrophones Applications
摘要： This study presents the electromechanical properties of the 3-3 piezoelectric metamaterial based on variants of honeycomb (HC) structure. Three kinds of three-dimensional (3D) elastically anisotropic and piezoelectrically active HC structures were introduced, namely, conventional HC (3D-CHC), a re-entrant HC (3D-RE) and a semi-re-entrant HC (3D-SRE). Highly porous 3D finite element models of the mentioned three kinds of metamaterials were developed and the role of ligament orientation on their effective elastic, piezoelectric and dielectric properties was completely characterized. The intrinsic symmetry of HC structure was utilized and simplified mixed boundary conditions equivalent to periodic boundary conditions were recognized. In comparison to their bulk constituent, all the 3-3 type piezoelectric HC networks exhibited an enhanced response, especially for the longitudinal poling. The normalized figures of merit show a mild dependence on the angle θ and the underlying deformation mechanisms associated with the zero, positive and negative Poisson’s ratios. Figures of merit such as hydrostatic strain coefficient (hd), the hydrostatic figure of merit (ghhd) and the acoustic impedance (Z) reached their best values at small angles, i.e., θ=30°. Longitudinally poled networks exhibited four order of magnitude increase in their hydrostatic figure of merit (foam to solid ratio >10,000) and one order of magnitude decrease in the acoustic impedance indicating their applicability for the design of hydrophones.
关键词： piezoelectric materials,auxetic smart structures,metamaterials,electromechanical properties,cellular materials,honey comb structures,unit cell method
更新于2025-09-23 15:19:57
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Metamaterials and chiral sensing: a review of fundamentals and applications
摘要： Chirality, a property of broken mirror symmetry, prevails in nature. Chiral molecules show different biochemical behaviors to their mirror molecules. For left or right circularly polarized lights, the fundamental chiral states of electromagnetic fields interact differently with chiral matter, and this effect has been used as a powerful tool for the detection of chiral molecules. This optical sensing, also termed chiral sensing, is not only easy to implement but also non-invasive to the analytes. However, the measurements made by the optical sensing of chiral molecules are challenging, as chiroptical signals are extremely weak. Recent years have seen active research efforts into metamaterial and plasmonic platforms for manipulating local fields to enhance chiroptical signals. This metamaterial approach offers new possibilities of chiral sensing with high sensitivity. Here, we review the recent advances in chiral sensing using metamaterial and plasmonic platforms. In addition, we explain the underlying principles behind the enhancement of chiroptical signals and highlight practically efficient chiral sensing platforms. We also provide perspectives that shed light on design considerations for chiral sensing metamaterials and discuss the possibility of other types of chiral sensing based on resonant metamaterials.
关键词： chiral sensing,chiral molecules,optical rotatory dispersion (ORD),chiroptical spectroscopy,circular dichroism (CD),enantiomers,plasmonics,metamaterials,optical spectroscopy
更新于2025-09-19 17:15:36
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Fractal Analysis - Applications in Physics, Engineering and Technology || Fractals in Antennas and Metamaterials Applications
摘要： Recently, telecommunications systems have been requiring more advanced features in the design and operation. Among others a smaller size of devices, which can be integrated for multiple mobile communications systems, applied in one user's device board, such as PDA or smartphone. Moreover, the cost of mass production should be minimized as much as possible. To meet part of that request, the antennas of these devices should have small size, lower weight, operating in multiple frequency bands and/or be broadband. There are many research methods to achieve this goal, one of which is using the fractal geometries for the shape of antenna elements. In recent years, there are many fractal shapes that have been proposed for such applications, and the designed antennas have significantly improved antenna features such as smaller size, operating in multi-frequency bands, with improved power gain and efficiency. In recent years, the new approach for modern antenna the metamaterials, MTM, is adopted, and sometimes that based on the fractal geometry is adopted.
关键词： fractal geometries,fractal antenna,antenna array,efficiency,fractal dimension,IFS,metamaterials,power gain,MTM,multiband,antenna elements,compact size
更新于2025-09-19 17:15:36
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A bi-functional illusion device based on transformation optics
摘要： An illusion device based on shifting distance concept has been investigated using linear coordinate transformation method. Distinguishing from the previously designed illusion devices, we construct the shift-illusion device featuring resizing and rotating for both active and passive scatterers, in case; if the shifting-region and physical space share the same origin point. Similarly, when the shifting-region is foreign to the designed device, the proposed illusion design performs as a rotation and relocation-shifting device to change the location of the scatterer. In addition, these proposed devices behave like the stealth effect in the absence of any scatterer as the outer-boundary field distribution is not disturbed. Meanwhile, the proposed concept is further extended for different mapping style to validate the shifting-illusion concept. The constitutive parameters of the proposed devices are homogeneous, which makes it more appreciable for real implementations. It is expected that the proposed design will find potential applications in illusion devices, such as objects protection, and camouflage etc.
关键词： Invisibility cloaks,transformation optics,metamaterials
更新于2025-09-19 17:15:36
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The Application of Least-Squares Finite Element Method to Simulate Wave Propagation in Bianisotropic Media
摘要： The finite element method (FEM) has been one of the major numerical techniques for electromagnetics (EM) ever since the introduction of the spurious-free edge element. On the other hand, a so-called least-squares finite element method (LSFEM) is becoming increasingly popular due to its unique properties. For instance, the generated stiffness matrix is positive definite. Effort has been made to apply this node-element-based LSFEM to model EM problems, mostly in the theoretical aspect. In this paper, we will use normalized Maxwell’s equations incorporated with the constitutive relations of bianisotropic media, which represents the most general cases in the linear regime. Subsequently, the corresponding variational formulation is derived, followed by the generation of matrix systems. We then implement and validate various boundary conditions. Further we apply this scheme to simulate wave scattering in the presence of bianisotropic media that are categorized into 3 types. A good convergence rate and agreement between the LSFEM results and the referenced solutions has been achieved, which proves the Lagrange-element-based LSFEM as a feasible alternative to the edge-element-based FEM currently used in EM modeling.
关键词： Electromagnetic metamaterials,Electromagnetic propagation,Finite element analysis
更新于2025-09-19 17:15:36
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Retrieving effective material parameters of metamaterials characterized by nonlocal constitutive relations
摘要： The parameter retrieval is a procedure in which effective material properties are assigned to a given metamaterial. A widely used technique bases on the inversion of reflection and transmission from a metamaterial slab. Thus far, local constitutive relations have been frequently considered in this retrieval procedure to describe the metamaterial at the effective level. This, however, is insufficient. The retrieved local material properties frequently fail to predict reliably the optical response from the slab in situations that deviate from those that have been considered in the retrieval, e.g., when illuminating the slab at a different incidence angle. To significantly improve the situation, we describe here a parameter retrieval, also based on the inversion of reflection and transmission from a slab, that describes the metamaterial at the effective level with nonlocal constitutive relations. We retrieve the effective material parameters at the example of a basic metamaterial, namely, dielectric spheres on a cubic lattice but also on a more advanced, anisotropic metamaterial of current interest, i.e., the fishnet metamaterial. We demonstrate that the nonlocal constitutive relation can describe the optical response much better than local constitutive relation would do. Our approach is widely applicable to a large class of metamaterials.
关键词： nonlocal constitutive relations,spatial dispersion,parameter retrieval,metamaterials,homogenization
更新于2025-09-19 17:15:36
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Single-Layer Bifacial Metasurface: Full-Space Visible Light Control
摘要： Optical metasurfaces have attracted considerable attention thanks to their unprecedented ability to control the electromagnetic properties of light in subwavelength scale. These metasurface-integrated devices not only have the merit of compact form factor but also exhibit some better performance in comparison with conventional bulk optic devices. In this work, a novel metasurface that enables full-space light control is realized, offering an unconventional functionality that provides a new foothold for metasurface integration in optics. Multipolar interference and Pancharatnam–Berry phase are combined with each other and suggested as a physical background for the proposed device. As an example of the functionality, asymmetric beam steering and hologram generation are proposed and measured experimentally. As far as it is known, this is the first work achieving full-space control in visible range. Thanks to its manufactural ease and unprecedented function capability, this work will offer innovative potentials to be utilized in various integrated optic devices that need miniaturization or implementation of ingenious and light-weight optical components used in optical systems for photography, microscopy, computer vision, etc.
关键词： beam steering,metamaterials,multifunctional devices,holography,metasurfaces
更新于2025-09-19 17:15:36
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Existence Conditions of High-k Modes in Finite Hyperbolic Metamaterials
摘要： The capability to support optical waves with very large wave vectors (high-k) is one of the principle features of hyperbolic metamaterials (HMMs). These waves play the key role in HMM applications such as imaging and lifetime engineering. E?ective medium approximation (EMA) as widely used analytical method to predict HMMs behavior, has shortcomings in calculating high-k modes of practical structures. EMA is applicable to a subwavelength unit cell of implicitly in?nite periodic structures. Using conventional EMA, in the present paper, boundary e?ects and spatial dispersion are taken into consideration to properly compute the high-k modes of ?nite-thickness multilayer HMMs. Applying nonlocal homogenization to stacks of alternating metal-dielectric layers, the corresponding e?ective medium is examined as a high-k waveguide sandwiched between the substrate and an ambient superstrate. The developed theory enables us to recognize two types of bulk waves coined as short-range and long-range propagating modes. Number of such modes as well as their cuto? conditions are quanti?ed for the ?rst time. Validity of the developed theory is veri?ed both numerically by rigorous simulations of the multilayer structures with the transfer matrix method and experimentally by optical characterization of the HMMs in infrared regime.
关键词： subwavelength metal-dielectric multilayers,e?ective medium theory,high-k modes,hyperbolic metamaterials
更新于2025-09-19 17:15:36
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Quad-Spectral Perfect Metamaterial Absorber at Terahertz Frequency Based on a Double-Layer Stacked Resonance Structure
摘要： Development of multispectral perfect light absorbers for applications in biological sensing, spectroscopic imaging, and selective thermal emitters is urgently required. Unfortunately, current multispectral absorbers are typically only based on a combination of fundamental resonances of multiple resonators using the design concepts of a coplanar superunit structure or multiple vertically stacked layers, which does not introduce new resonances while such structures are difficult to fabricate. In this work, a type of quad-spectral absorber formed by a double-layer stacked resonant structure is presented and demonstrated. Numerical simulations show that the suggested structure can achieve near 100% absorption at four frequency bands. The quad-spectral absorption results from excitation of two sets consisting of the fundamental mode and third-order resonance of the designed structure. The suggested device is insensitive to the polarization of the incident light due to the high degree of symmetry of the resonance structure. Device parameters are investigated to further explore the physical origin of the quad-spectral absorption. Moreover, it is revealed that the number of resonance peaks can be further increased by employing one more layer.
关键词： Metamaterials,multispectral absorption,terahertz
更新于2025-09-19 17:15:36
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Modelling the propagation of electromagnetic waves across complex metamaterials in closed structures
摘要： Metamaterials are currently one of the most popular fields in microwave technology because their particular electromagnetic properties lead to a plenty of very relevant applications, both military and civilian. Additionally, the analysis and design of microwave components based on this kind of materials is one of the more challenging problems found by the applied electromagnetism community due to the complexity introduced in the mathematical formulation by their constitutive relationships. The most general case of metamaterial is the bi-anisotropic one, where both the electric field and the electric induction simultaneously depend on the magnetic field and the magnetic induction. In this paper, we present a new and powerful Finite Element Method scheme valid for the analysis of the most general waveguides, filled with lossy bi-anisotropic linear materials. Edge elements have been used in order to prevent the appearance of spurious solutions and the final eigensystems are very sparse, thus allowing a great memory and computing time saving.
关键词： Bi-anisotropic metamaterials,Microwave engineering,Weighted residuals method,Finite Element Method
更新于2025-09-19 17:15:36