Phys.org March 6, 2024 Zero-index metamaterials (ZIMs) can support uniform electromagnetic field distributions at any frequency, but their applications are hampered by the ZIM’s homogenization level—only 3-unit cells per free-space wavelength, which is fundamentally limited by the low-permittivity inclusions and background matrix. An international team of researchers (USA – Stanford University, China) demonstrated a highly homogeneous microwave ZIM with an over threefold increase in the homogenization level by filling high-permittivity SrTiO3 ceramic pillars in BaTiO3 background matrix. They achieved an antenna, and a concave lens with a focal length of as short as 1λ0… read more. Open Access TECHNICAL ARTICLE
Category Archives: Metamaterials
A new optical metamaterial makes true one-way glass possible
Phys.org February 14, 2024 The nonreciprocal magnetoelectric effect, also known as the Tellegen effect, promises several groundbreaking phenomena connected to fundamental and applied physics. An international team of researchers (Finland, Sweden, USA – University of Pennsylvania, Stanford University) proposed a three-dimensional metamaterial with an isotropic and resonant Tellegen response in the visible frequency range. The metamaterial was formed by randomly oriented bimaterial nanocylinders in a host medium. Each nanocylinder consisted of a ferromagnet in a single-domain magnetic state and a high-permittivity dielectric operating near the magnetic Mie-type resonance. The proposed metamaterial required no external magnetic bias and operated on the […]
Metamaterials: Time crystal gives light a boost
Nanowerk April 25, 2023 Photonic time crystals are artificial materials whose electromagnetic properties are uniform in space but periodically vary in time. The synthesis of these materials and experimental observation of their physics remains very challenging because of the stringent requirement for uniform modulation of material properties in volumetric samples. An international team of researchers (Finland, Germany, USA – Stanford University) has extended the concept of photonic time crystals to metasurfaces. They demonstrated that time-varying metasurfaces not only preserve key physical properties of volumetric photonic time crystals despite their simpler topology but also host common momentum bandgaps shared by both […]
Mechanical metamaterials: Toughness and design criteria
Phys.org February 21, 2022 Rapid progress in additive manufacturing methods has created a new class of ultralight mechanical metamaterials with extreme functional properties. Their application is ultimately limited by their tolerance to damage and defects, but an understanding of this sensitivity has remained elusive. An international team of researchers (UK, USA – Virginia Polytechnical Institute and State University, UCLA, industry) used metamaterial specimens consisting of millions of unit cells, to show that not only is the stress intensity factor, as used in conventional elastic fracture mechanics, insufficient to characterize fracture, but also that conventional fracture testing protocols are inadequate. With […]
3D Kirigami Building Blocks Designed To Make Dynamic Metamaterial Structures
ScitechDaily.com August 11, 2021 In a proof-of-concept study a team of researchers in the US (North Carolina State University, Yale University) cut bulk materials into spatially closed-loop to construct a new class of 3D kirigami metamaterials. The module is transformable with multiple degrees of freedom that can transform into versatile distinct daughter building blocks. Depending on how the cubes are connected to each other, the building blocks can be folded into more than 300,000 different designs. Their conformable assembly creates a wealth of reconfigurable and disassemblable metamaterials with diverse structures and unique properties, including reconfigurable 1D column-like materials, 2D lattice-like […]
Metamaterials research challenges fundamental limits in photonics
Phys.org August 10, 2021 Previous research was limited to modifying either absorption or refraction in metamaterials. Researchers at Cornell University have demonstrated that if both properties are modulated in time, it is possible to absorb electromagnetic waves much more efficiently than in a static structure, or in a structure in which either one of these two degrees of freedom is modulated individually. They combined these two aspects together to create a much more effective system. The findings may lead to the development of new metamaterials with wave absorption and scattering properties that far outperform what is currently available. The research […]
The first observation of the superscattering effect of metamaterials
Phys.org June 23, 2021 Superscattering effects, such as stopping wave propagation in an air channel, have not been verified from illusion devices physically because of the challenge of metamaterial design, fabrication, and material loss. Researchers in China have implemented a big metamaterial superscatterer, and experimentally demonstrated its superscattering effect at microwave frequencies by field-mapping technology. They confirmed that superscattering is originated from the excitation of surface plasmons. They experimentally showed that an invisible gateway integrated with superscatterer could stop electromagnetic waves in an air channel with a width much larger than the cutoff width of the corresponding rectangular waveguide. The […]
Smart metamaterials that sense and reprogram themselves
Phys.com November 11, 2019 As proof of concept, an international team of researchers (USA – Duke University, UK, China) proposed and developed a smart digital-coding metasurface with self-adaptive capacity for reprogrammable functionality. A sensor on the metasurface detected specific features surrounding the construct in the environment and delivered them to a microcontroller unit (MCU) which independently determined reactions to these variations and then instructed the FPGA via coding patterns, to change the metasurface configuration in real time. The smart metasurfaces achieved self-adaptive reprogrammable functionality automatically based on the surface-installed sensing-feedback system and calculation software. The team envisions the preliminary work […]
Harry Potter had magic – We have metamaterials
Nanowerk June 15, 2018 Researchers at Northeastern University have developed a deep-learning-based model, comprising two bidirectional neural networks assembled by a partial stacking strategy, to automatically design and optimize three-dimensional chiral metamaterials with strong chiroptical responses at predesignated wavelengths. The model can help to discover the intricate, nonintuitive relationship between a metamaterial structure and its optical responses from a number of training examples. This approach realizes the forward prediction of optical performance much more accurately and efficiently and helps inversely retrieve designs from given requirements…read more. TECHNICAL ARTICLE