Metamaterial Research Articles

Metallic Structures Based on Zinc Oxide Film for Enzyme Biorecognition

Two structures (Ag/ZnO/ITI/glass: #1 sample and Ag/ZnO/SiO2/Si: #2 sample) are investigated, on the one hand, from the point of view of the formation of evanescent waves in the gratings of metal strips on the structures when the incident TEz wave in the radio frequency range is used. The simulation of the formation of evanescent waves at the edge of the Ag strips, with thicknesses in the range of micrometers, was carried out before the test in the subwavelength regime, with the help of a new improved transducer with metamaterial (MM) lenses. By simulation, a field snapshot was obtained in each sequence of geometry. The evanescent waves are emphasized in the plane XY, due to the scattering of the field on the edge of the strips. On the other hand, ZnO nanoparticles are investigated as a convenient high-efficiency biodetection material, where these structures were used as a biosensitive element to various enzymes (glucose, cholesterol, uric acid, and ascorbic acid). The obtained results demonstrate that the investigated structures based on ZnO nanostructures deposited on different supports are fast and sensitive for enzyme detection and can be successfully incorporated into a device as a biosensing element.

A Metamaterial-Based Absorber for Liquid Sensing in Terahertz Regime

A metamaterial (MM) absorber and its application in liquid sensing are proposed in this article. The unit cell of the sensor structure consists of two quartz substrates with metallic patterns and sheets printed on their surfaces. The liquid tunnel with optimal thickness is created by placing the glass micro-pearls between the quartz substrates. By incorporating dual semitoroidal resonators, the enhanced spectral shift per refractive index unit (RIU) improves the sensitivity of the proposed design effectively, and sensitive frequency detection with 52.50 GHz/RIU is numerically demonstrated. Moreover, we experimentally demonstrate its application for determining ethanol and sucrose solutions with different concentrations and three commonly used oils. A good agreement with the experiments and simulations is obtained. In addition, the proposed sensor has the advantages such as compact size, easy fabrication, and reusability, which offers excellent potential in food industry applications.

Seismic Composite Metamaterial: A Review

The modern construction revolution throughout the past two decades has brought the need for ground vibration mitigation, and this has been one of the major study areas. These studies were mainly focused on the effect of forestation on vibration reduction as the available natural metamaterial. Physical methods such as the finite element method and the boundary conditions of 2D and 3D applications in ground vibration reduction have been developed. Many researchers, scientists, and organizations in this field have emphasized the importance of these methods theoretically and numerically. This paper presents the historical context of resonant metamaterials (MMs), the current progress of periodic 2D and 3D structures, and the possible future outcomes from the seismic metamaterials (SMs), and it relates them with their elastic counterparts to the natural metamaterial (NMs). The idea of bandgaps (FBGs) in the frequency range of interest is reviewed and discussed in some detail. Moreover, the attenuation associated with ground vibrations, noise, seismology, and the like is explained by managing the peculiar mechanisms of ground vibrations. However, a comprehensive computational review focuses on shielding MMs for ground vibration mitigation in urban areas. This phenomenon led to unique features for various techniques to control the bandgap width for various construction applications. Ecological solutions involve the creation of an economic, environmentally based seismic shield for both the Bragg scattering and the local resonance bandgaps. Reportedly, additive studies based on numerical simulation and experiments have improved the functionality of the 2D and 3D periodic structures. It was found that the mechanical properties differ (i.e., stiffness, Poisson’s ratio, and bulk density) and that the geometrical parameters (i.e., lattice, model dimensions, distance from vibration sources, and number of periodic structures) exhibited strong effects on the width and location of the derived FBGs. The geometrical properties of the used unit cell have a strong effect on the attenuation mechanism. Although deep analysis was created in much of the previous research, it was revealed, based on that research, that the attenuation mechanism is still unclear. However, this review article presents a detailed exposition of the recent research progress of the seismic metamaterials, including 2D, 3D, and the main mechanisms of the theoretical backgrounds of energy attenuation. It also summarizes the effects of the factors on the width and location of the bandgaps at a low frequency. In addition, the natural metamaterials and the study of the urban environment are surveyed. The major findings of this review involve the effectiveness of NMs for different functionalities in ground vibration attenuation, which leads to diverse purposes and applications and proposes a roadmap for developing natural materials for clean and quiet environments.

Extraction of the Electromagnetic Parameters of a Metamaterial Using the Nicolson–Ross–Weir Method: An Analysis Based on Global Analytic Functions and Riemann Surfaces

The characterization of electromagnetic metamaterials (MMs) plays a fundamental role in their engineering processes. To this end, the Nicolson–Ross–Weir (NRW) method is intensively used to recover the effective parameters of MMs, even though this is affected by the branch ambiguity problem. In this paper, we face this issue in the context of global analytic functions and Riemann surfaces. This point of view allows us to rigorously demonstrate the mathematical foundations of an algorithmic approach for avoiding the branch ambiguity problem, in which the phase unwrapping method is merged with K-K relations for recovering the effective parameters of an MM. In addition, exploiting the intimate relationship between the K-K relations and the Hilbert transform, a simple variant of the above algorithm is presented.

Machine Learning of Implicit Combinatorial Rules in Mechanical Metamaterials.

Combinatorial problems arising in puzzles, origami, and (meta)material design have rare sets of solutions, which define complex and sharply delineated boundaries in configuration space. These boundaries are difficult to capture with conventional statistical and numerical methods. Here we show that convolutional neural networks can learn to recognize these boundaries for combinatorial mechanical metamaterials, down to finest detail, despite using heavily undersampled training sets, and can successfully generalize. This suggests that the network infers the underlying combinatorial rules from the sparse training set, opening up new possibilities for complex design of (meta)materials.

Designing and Implementing Sliding Gain/Pattern Controller Belt for Heat-Sink Antennas Operating at C-Band

The foremost method to exhaust heat sourced from electronic devices is to use heat sinks. However, in practice, these structures behave as actual antennas and cause interference problems. The selected heat sink like many others is performing like a real antenna whose gain at 4.9 GHz is ~ 7 dBi both in simulation and measurement. In this study, a novel gain (radiation pattern) controlling belt made up of a metamaterial (MTM) structure was designed and dressed to the heat-sink antenna. The effect of the position of the belt on the antenna pattern is investigated. The sliding position of the belt which allows for dynamic gain control varies the antenna gain between 3.38 and 7.36 dBi (~ 7 dB in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\theta }$ </tex-math></inline-formula> angle and ~ 9 dB in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\emptyset }$ </tex-math></inline-formula> angle). Maximum gain enhancement reaches up to 18.43 dB and maximum suppression ratio reaches up to 21.36 dB for the entire angle.

Metamaterial-Inspired Interaction Structure for MW-Level Klystron at 714 MHz

A metamaterial (MTM)-inspired interaction structure for MW-level klystron at 714 MHz is proposed. The electromagnetic characteristics of MTM-inspired resonant cavities with single-bridge complementary electric split ring resonators (CeSRRs) are studied, and the cold-tested results confirm the feasibility of miniaturizing the resonant cavity. Furthermore, the beam–wave interaction simulation for the interaction structure constructed by MTM-inspired resonant cavities with single-bridge CeSRRs is carried out, demonstrating 2.28 MW of output power at 714 MHz for a 100 kV, 40 A electron beam. The radius and length of the MTM-inspired interaction structure are 1/2 and 2/3 of the conventional counterparts, respectively. The promising performance makes it attractive for future applications such as linacs.

Transmittance properties of one-dimensional metamaterial nanocomposite photonic crystal in GHz range

We have theoretically demonstrated and explored the transmittance characteristics of a one-dimensional binary photonic crystal composed of metamaterial (MM) and nanocomposite (NC) layers. The NC layer was designed from silver nanoparticles (Ag-NPs) in a host material as Yttrium oxide (Y2O3). Using the transfer matrix approach (TMM), the optical properties of a one-dimensional binary periodic structure having MM and NC layers in the Giga Hertz (GHz) range were examined. The filling fractions of nanoparticles have been explored to see their effect on the effective permittivity of NC materials. Furthermore, the transmittance properties of the suggested structure were investigated at various incident angles for the transverse electric (TE) polarization. In addition to that, different parameters, such as the thickness of the MM layer, the permittivity of the host dielectric material, the filling fraction, and the thickness of the NC layer are also taken into account. We also discussed the effect of these parameters on the width of the photonic bandgap (PBG). With the optimum values of the optical parameters of NC layer, this research could open the way for better photonic crystal circuits, splitters, switches and others.

Time-varying Metamaterial-enabled Directional Modulation Schemes for Physical Layer Security in Wireless Communication Links

Novel transmission schemes, enabled by recent advances in the fields of metamaterial (MTM), leaky-wave antenna (LWA) and directional modulation (DM), are proposed for enhancing the physical layer (PHY) security. MTM-LWAs, which offer compact, integrated, and cost-effective alternatives to the classic phased-array architectures, are particularly of interest for emerging wireless communication systems including Internet-of-Things. The proposed secure schemes are devised to accomplish the functionalities of directional modulation (DM) transmitters for orthogonal frequency-division multiplexing (OFDM) and non-contiguous OFDM transmissions, while enjoying the implementation benefits of MTM-LWAs. Specifically, transmitter architectures based on the idea of time-modulated MTM-LWA have been put forth as a promising solution for PHY security for the first time. The PHY security for the proposed schemes are investigated from the point of view of both passive and active attacks where an adversary aims to decode secret information and feed spurious data to the legitimate receiver, respectively. Numerical simulations reveal that even when the adversary employs sophisticated state-of-the-art deep learning based attacks, the proposed transmission schemes are resistant to these attacks and reliably guarantee system security.

Meta Material that Acts as a Permanent Energy Source

Meta Material that Acts as a Permanent Energy Source

Polarization-insensitive broadband perfect metamaterial absorber in the optical region

Metamaterials (MTMs) have various applications like plasmonic sensors, light trapping, light detector, color imaging, real invisible clock, magnetic resonance imaging, thermal imaging, solar cells, etc. We have used CST software to simulate four nano-rings-based broadband MTM absorbers in this paper. The simulated structure consists of three layers in the form of a metal-dielectric-metal that exhibit a good impedance near unity with plasmonic resonance characteristics. Tungsten (W) is chosen as the metal and silicon dioxide (SiO2)as the dielectric. The designed structure exhibits an average absorption of 98.19% at the applied wavelength and also exhibits broadband absorption with almost perfect absorption. The physical dimensions, as well as the design of the proposed absorber, have been studied parametrically. Absorber performance has been investigated for transverse electric (TE) and transverse magnetic (TM) modes at wide angles up to 50°, which may be helpful for solar thermo-photovoltaic (STPV) and solar power harvesting device applications. For solar cell applications, we have calculated numerical values of short circuit current density (Jsc) and efficiency (η).

Microwave brain imaging system to detect brain tumor using metamaterial loaded stacked antenna array

In this paper, proposes a microwave brain imaging system to detect brain tumors using a metamaterial (MTM) loaded three-dimensional (3D) stacked wideband antenna array. The antenna is comprised of metamaterial-loaded with three substrate layers, including two air gaps. One 1 × 4 MTM array element is used in the top layer and middle layer, and one 3 × 2 MTM array element is used in the bottom layer. The MTM array elements in layers are utilized to enhance the performance concerning antenna’s efficiency, bandwidth, realized gain, radiation directionality in free space and near the head model. The antenna is fabricated on cost-effective Rogers RT5880 and RO4350B substrate, and the optimized dimension of the antenna is 50 × 40 × 8.66 mm3. The measured results show that the antenna has a fractional bandwidth of 79.20% (1.37–3.16 GHz), 93% radiation efficiency, 98% high fidelity factor, 6.67 dBi gain, and adequate field penetration in the head tissue with a maximum of 0.0018 W/kg specific absorption rate. In addition, a 3D realistic tissue-mimicking head phantom is fabricated and measured to verify the performance of the antenna. Later, a nine-antenna array-based microwave brain imaging (MBI) system is implemented and investigated by using phantom model. After that, the scattering parameters are collected, analyzed, and then processed by the Iteratively Corrected delay-multiply-and-sum algorithm to detect and reconstruct the brain tumor images. The imaging results demonstrated that the implemented MBI system can successfully detect the target benign and malignant tumors with their locations inside the brain.

Meta Material that Acts as a Permanent Energy Source

Meta Material that Acts as a Permanent Energy Source

Metamaterial-Loaded 16-Printed Log Periodic Antenna Array for Microwave Imaging of Breast Tumor Detection

This article presents printed log periodic antennas with metamaterials for use in microwave imaging. A single layer of epsilon negative (ENG) metamaterial (MTM) array (1 × 6) of the unit cell is on the radiating patch. Adding a single negative metamaterial structure enhances the properties of far-field antennas, such as radiation pattern and gain, both of which are vital for breast imaging. Two frequency bands exhibit negative permittivity: 3–3.3 GHz and 3.6–4.5 GHz. In the operating band, the proposed antennas have achieved a maximum gain of 5.5 dBi and impedance bandwidth of 3 GHz (2–5 GHz) with a reflection coefficient less than −10 dB. At the lowest operating frequency of 2 GHz, the electrical dimensions of this designed antenna are 0.34λ × 0.26λ × 0.01λ. All 16 transceiver antennas are arranged vertically in a circular pattern around the phantom, each acting as a transmitter and the rest as receivers. The system design is carried out with the electromagnetic simulators CST and HFSS. After receiving the extracted data, the data are postprocessed using the MATLAB software and the delay multiply and sum (DMAS) imaging algorithm. Based on the reconstructed image, it is evident that the MTM-loaded antenna-based imaging system can detect many undesired tumors inside the breast phantom.

Meta Material that Acts as a Permanent Energy Source

Meta Material that Acts as a Permanent Energy Source

Massive metamaterial system-loaded MIMO antenna array for 5G base stations

An integrated massive multiple-input multiple-output (mMIMO) antenna system loaded with metamaterial (MTM) is proposed in this article for fifth-generation (5G) applications. Besides, achievement of duple negative (DNG) characteristics using a proposed compact complementary split-ring resonator (SRR), a broad epsilon negative metamaterial (ENG) with more than 1 GHz bandwidth (BW), and near-zero refractive index (NZRI) features are presented. The proposed mMIMO antenna consists of eight subarrays with three layers that operate in the 5G mind band at 3.5 GHz (3.40–3.65 GHz) with high port isolation between adjacent antenna elements compared to an antenna that does not use MTM. Each subarray has two patches on the top layer, while the middle and bottom layers have two categories of full and partial ground plans, respectively. Simulated, produced, and tested are 32 elements with a total volume of 184 × 340 × 1.575 mm3. The measured findings reveal that the sub-6 antenna has a better than 10 dB reflection coefficient (S11), a lower than 35 dB isolation, and a peak gain of 10.6 dBi for each subarray. Furthermore, the recommended antenna loaded with MTM has demonstrated good MIMO performance with an ECC of less than 0.0001, total efficiencies of more than 90%, more than 300 MHz bandwidth, and an overall gain of 19.5 dBi.

Ballistic dynamics of flexural thermal movements in a nanomembrane revealed with subatomic resolution.

Flexural oscillations of freestanding films, nanomembranes, and nanowires are attracting growing attention for their importance to the fundamental physical and optical properties and device applications of two-dimensional and nanostructured (meta)materials. Here, we report on the observation of short–time scale ballistic motion in the flexural mode of a nanomembrane cantilever, driven by thermal fluctuation of flexural phonons, including measurements of ballistic velocities and displacements performed with subatomic resolution, using a free electron edge-scattering technique. Within intervals <10 μs, the membrane moves ballistically at a constant velocity, typically ~300 μm/s, while Brownian-like dynamics emerge for longer observation periods. Access to the ballistic regime provides verification of the equipartition theorem and Maxwell-Boltzmann statistics for flexural modes and can be used in fast thermometry and mass sensing during atomic absorption/desorption processes on the membrane.

Symmetric Engineered High Polarization-Insensitive Double Negative Metamaterial Reflector for Gain and Directivity Enhancement of Sub-6 GHz 5G Antenna.

A symmetric engineered high polarization-insensitive double negative (DNG) metamaterial (MM) reflector with frequency tunable features for fifth-generation (5G) antenna gain and directivity enhancement is proposed in this paper. Four identical unique quartiles connected by a metal strip are introduced in this symmetric resonator that substantially tunes the resonance frequency. The proposed design is distinguished by its unique symmetric architecture, high polarization insensitivity, DNG, and frequency tunable features while retaining a high effective medium ratio (EMR). Moreover, the suggested patch offers excellent reflectance in the antenna system for enhancing the antenna gain and directivity. The MM is designed on a Rogers RO3010 low loss substrate, covering the 5G sub-6GHz band with near-zero permeability and refractive index. The performance of the proposed MM is investigated using Computer Simulation Technology (CST), Advanced Design Software (ADS), and measurements. Furthermore, polarization insensitivity is investigated up to 180° angles of incidence, confirming the identical response. The 4 × 4 array of the MM has been utilized on the backside of the 5G antenna as a reflector, generating additional resonances that enhance the antenna gain and directivity by 1.5 and 1.84 dBi, respectively. Thus, the proposed prototype outperforms recent relevant studies, demonstrating its suitability for enhancing antenna gain and directivity in the 5G network.

A vanadium dioxide-based metamaterial with quatrefoil and circle loaded structure on flexible polyamide substrate for terahertz applications

In this study, a novel broadband metamaterial (MTM) absorber is proposed, which is based on vanadium dioxide (VO2) resonators coated onto a flexible polyamide substrate. The VO2 resonator is in the form of a quatrefoil and circle-loaded complementary square split ring resonator (CSSRR), which is fine tuned to operate in the terahertz range. The MTM design and simulation were carried out using Computer Simulation Technology (CST) software, by which different layouts were investigated to achieve the optimum structure. The results showed the presence of two pronounced peaks for the proposed MTM structure at 0.88 and 1.42 THz. The absorption peaks were found to be insensitive to the wave polarization and incident angle from 0° to 90°. The absorption mechanism of the MTM was investigated considering the insulating and metallic states of VO2. The results were in a good agreement with those calculated using high frequency simulated structure (HFSS) software. The flexible nature of the proposed MTM design makes it a viable candidate for non-planar and conformal geometry applications in stealth technology, and terahertz imaging.

Millimeter-Wave Applications of MIMO Antenna

For millimetre wave technology (25GHz–30GHz), a rectangular MIMO antenna is created. The design of this antenna radiates at a frequency of 27GHz and comprises of nine numbers of cells arranged in a 3x3 array. Each unit cell has an SRR and a hexagonal patch with a Meta material substrate (MTM). The developed antenna has a gain of 3db and operates between 25 and 30 GHz. The proposed configuration has a small overall antenna size of 52 mm by 23 mm, making it simple to build.