What is the best split ring design for metasurface absorbers?3 answersThe best split ring design for metasurface absorbers varies depending on the specific requirements and applications. Several designs have been proposed in the literature. Amer et al. proposed a polarization-insensitive broadband metasurface absorber based on square split-ring resonators (SSRRs) loaded with lumped resistors. Bhati and Jain proposed an ultrathin perfect metamaterial absorber based on dual split-ring with a cross-resonator. Amer et al. also designed a broadband electromagnetic metasurface absorber with two split-ring resonators forming an X-shaped structure. Wang et al. proposed a metal-insulator-metal metasurface structure with an outer ring and embedded split rings. Hannan et al. introduced a modified-segmented split-ring based symmetric metamaterial absorber. Each of these designs has its own advantages and performance characteristics, such as wide-angle reception, multiband absorption, and high sensitivity. The choice of the best split ring design depends on the specific requirements of the application.
What are the different types of metamaterials?5 answersMechanical metamaterials, also known as architected materials, are designed composites that aim to have elastic behaviors and effective mechanical properties beyond those of their individual ingredients. These metamaterials can exhibit extreme ordinary linear elastic behavior, negative effective properties, behavior beyond classical linear elasticity, and quasi-crystalline structures. Auxetic metamaterials, which expand transversely when stretched, are widely used in engineering fields. Programmable metamaterials have been developed, including triangular, square, and honeycomb lattice metamaterials, which can achieve large deformation and auxetic behaviors. Three-dimensional metallic metamaterials with tailorable thermo-mechanical properties have also been designed, allowing for the tunability of Poisson's ratio, coefficient of thermal expansion, and Young's modulus. Additionally, flexible metamaterials made of viscoelastic materials have been explored, exhibiting programmable deformations and sensitivity to loading rate.
What is the best design for resonator in planar metasurface absorbers?3 answersThe best design for resonators in planar metasurface absorbers depends on the specific requirements and applications. One design is a six-band terahertz perfect metasurface absorber (PMSA) composed of a single circular-split-ring (CSR) structure placed over a ground-plane by a dielectric substrate. Another design is an acoustic metasurface absorber (AMA) composed of micro-perforated plates (MPPs) and impedance matching coiled-up cavities (IMCCs) for flexible and accurate broadband sound absorption. A wideband graphene-inspired reconfigurable metasurface absorber based on elliptical-ovel-shaped cylindrical dielectric resonators is also proposed. Additionally, a tunable triple-band absorber based on bulk-Dirac-semimetal (BDS) metasurface is suggested for the terahertz range. Lastly, an ultrathin planar acoustic diffuser using a monolayer of Helmholtz-like resonators is designed for producing narrowband diffuse reflection with high uniformity. Each design offers unique advantages and can be chosen based on the specific resonator requirements and desired performance characteristics.
What is already existing in the use of metamaterials in waveguides?5 answersMetamaterials have been used in waveguides to achieve unique properties not achievable in conventional waveguides, such as propagation of backward waves, modes below the cut-off frequencies of the conventional fundamental mode, and zero group velocity. Different waveguide geometries, such as parallel plates, rectangular or cylindrical cross-sections, and hollow-core waveguides, have been demonstrated experimentally. The anisotropy of the waveguide filler material can be uniaxial or biaxial, depending on the orientation of the structure. Corrugated waveguides can be represented as cylindrical waveguides with smooth metamaterial coatings when the corrugations are subwavelength, resulting in novel dispersive effects on signals traveling inside the waveguide. Silicon-based metamaterial structures have been designed and characterized, with an effective dielectric constant analyzed and validated through simulations and measurements. Additionally, tunable acoustic metamaterials have been proposed, where the resonance frequency of the cell can be changed by altering the magnetic field, allowing for control of bandgaps, transmission loss, and waveguides.
Metamaterial for radar cross section reduction?5 answersMetamaterials have been widely studied for radar cross section (RCS) reduction. Different methods have been explored to achieve RCS reduction, including the use of metamaterial structures. By loading metamaterial structures onto an antenna, the electromagnetic characteristics of the antenna can be manipulated, resulting in a reduced RCS. Various types of metamaterial antennas have been investigated for RCS reduction, such as L-structured and Square-structured fractal metamaterial antennas. Additionally, metasurfaces with diffusive parabolic phase distributions have been designed to achieve wide-angle low scattering and wideband RCS reduction. Another approach involves using a digital coding metasurface controlled by optical light to dynamically manipulate the electromagnetic wave and reduce RCS. These advancements in metamaterial design offer promising applications in stealth and military technology.
How can we design metamaterials to achieve a desired acoustic response?5 answersAcoustic metamaterials can be designed to achieve a desired acoustic response through various approaches. One approach is the use of a system-based design process, which relies on the expertise of specialists and evaluates target criteria at the end of the design phase. Another approach involves tailoring the structure of the metamaterial to exhibit arbitrary effective constitutive parameters, allowing for wavefront modulation, cloaking, sub-diffraction focusing, and other extraordinary effects. Additionally, a deep learning-based approach using conditional generative adversarial networks has been proposed. This approach generates cell candidates based on desired transmission characteristics, allowing for the design of problem-specific applications. Furthermore, the rational design of micro-features in the repeating unit cells of acoustic metamaterials can address specific acoustic problems. Overall, these approaches provide insights and methods for designing metamaterials with desired acoustic responses.