Resonant Metamaterials Research Articles

Nonlocal interactions on dynamic growth of an inclusion in locally resonant elastic wave metamaterials

Nonlocal interactions on dynamic growth of an inclusion in locally resonant elastic wave metamaterials

Sensitivity Enhancement of THz Metamaterial by Decoupling its Resonance from the Substrate's Fabry–Pérot Oscillations

AbstractLC‐circuit‐based resonant metamaterials (MM) operating in the terahertz (THz) are proven to detect the presence of nanoparticles within the capacitive gap of nanoantennas, manifesting a red‐shift in the resonance frequency. Sensitivity reduction (reduced red‐shift) due to the interaction/coupling of the substrate's Fabry–Pérot (FP) oscillations with the MM resonance is discussed. This new discovery of coupling is more probable and intense in thicker semiconductor substrates used in standard complementary metal‐oxide semiconductor processes, due to the high density of the FP oscillations and thus the probability for coupling with the single MM resonance increases. This also results in reducing the quality factor (Q‐Factor) of MM resonance, as well as the dielectric response to nanoparticles spread on the MM surface, by reducing the resonance frequency shift (ΔF) and thus the sensitivity of resonant MM. A sensitivity restoration of the MM resonance's red‐shift by decoupling it from the FP oscillations after thinning down the substrate by standard backside polishing is shown. The research is based on a combination of rigorous CST system‐level simulations along with THz impedance spectroscopy laboratory experiments: up to a fivefold enhancement of sensitivity of the thinned substrate compared with the conventional thick substrates is shown. This work has potential applications in the high‐sensitivity detection of nanomaterials and bio‐sensing at ultra‐low concentrations.

Implementation of the Metamaterial Multiband Frequency Reconfigurable Antenna for IoT Wireless Standards

A reconfigurable metamaterial multiband antenna operating an octa-band resonating mode is designed for IoT wireless applications. Metamaterial cell split ring resonator (SRR) and quasi-complementary split ring resonator (CSRR) are printed on the back and front sides of the proposed antenna design to achieve the multiband characteristics. The PIN diode is implemented in a slotted ground section of the antenna structure to get different wireless standards by switching the diode ON/OFF. During reverse biased (OFF) mode of diode antenna operating at eight resonant frequencies 2.42, 4.34, 5.81, 8.45, 11.02, 13.98, 16.12, and 18.87 GHz covering the IoT wireless standards such as S, C, X, Ku, and K band to identify a variety of wireless applications such as WLAN, WAIC, ITU, Satellite, and radar communication. Simple structure, stable radiation pattern, multiband operation, frequency band reconfigurability feature, reasonable gain, and efficiency are the significant features of the proposed metamaterial multiband antenna.

Design of a novel graphene buzzle metamaterial refractometer for sensing of cancerous cells in the terahertz regime

This paper introduces a novel biosensor with enhanced sensitivity for detecting the dielectric constant. The biosensor utilizes a metamaterial buzzle resonator incorporated with a thin graphene layer measuring 35 nm, operating in the terahertz (THz) frequency range. The biosensor demonstrates remarkable performance, featuring a high average sensitivity of 495 GHz/RIU (7.64 dB/RIU) and a quality factor of 82. These attributes enable the biosensor to effectively differentiate between various types of cancer cells, including basal cell, breast cell, and cervical cell, Jurkat, MCF-7, and PC12. The biosensor's resonance frequency and peak attenuation (S11 dB) display considerable sensitivity to changes in the refractive index of the sample, thereby achieving excellent linear performance. As a result of developing these characteristics, the biosensor demonstrates to be highly effective in detecting and distinguishing cancer cells built on their dielectric properties. The sensor's sensitivity, combined with its capacity to distinguish between different cell types, makes it a promising tool for cancer finding and characterization. This Research presents a state-of-the-art biosensor capable of detecting the dielectric constant with remarkable sensitivity. This utilization of a metamaterial buzzle resonator and thin graphene layer in the THz regime, coupled with high average sensitivity, quality factor, and linear performance, enables effective discrimination of various cancer cell types. This biosensor holds great potential for advancing cancer detection and characterization techniques.

Multifunctional applications of topological valley-locked elastic waves

Topological valley metamaterial in classical wave systems has shown great potential for manipulating electromagnetic, acoustic, and elastic waves due to the defect-immune and lossless energy properties. The application prospects of topological valley material on signal processing, structural damage detection, and energy harvesting are worth exploring further. In this study, we combine the valley Hall effect and the tunneling effect of local resonant metamaterials to reveal some novel coupling transport phenomena in elastic systems. Some potential applications are explored experimentally and numerically. First, we implement a low-frequency (<1 kHz) valley-locked waveguide in heterostructures based on the topological valley edge state of the local resonant metamaterial. The robustness of the topological valley-locked waveguide under wide valley-locked layers, impurities, disorder, and bends is verified. Next, we introduce tunneling phenomena into the topological valley-locked waveguide, enabling the realization of an on-off controllable heterojunction by sandwiching crystals with different Dirac cones. The difference between the transmission characteristics of valley-locked waveguides under different tunneling layers (potential barrier and well) is revealed. Finally, we explore potential applications such as signal splitters, energy concentrators, and logical gates, both numerically and experimentally. Beyond the presented applications, this research has promising application prospects for vibration signal processing and high-performance energy harvesting.

Temperature controlled quasi-zero-stiffness metamaterial beam for broad-range low-frequency band tuning

Despite their engineering significance, locally resonant metamaterials are facing the challenge to cope with the need for broad-range band gap adjustment at low-frequencies. To tackle this problem, this study proposes using shape memory alloys (SMAs) to achieve temperature-controlled quasi-zero-stiffness (TC-QZS) metamaterial beam, which entails tunable and low-frequency band gap through ambient temperature changes. The basic configuration of the proposed TC-QZS resonator embraces a negative mechanism, steming from an SMA and a nonlinear geometrical structure. The stiffness of the positive stiffness mechanism can be effectively neutralised by the negative one, and the neutralisation can be adjusted based on temperature change applied to the SMA. The resultant stiffness variation yields broad-range tunability of the resonant frequency of the TC-QZS resonator. The band gap structure of the metamaterial beam is obtained using the transfer matrix method and verified by numerical simulation. Effects of dominant parameters on band gaps are scrutinized. Results show that the frequency range of the band gap can be continuously tuned from 26 to 69 Hz. This study provides guidance for the realisation of band gap tunibility over a wide frequnecy range and lays the groundwork for the development of elastic wave manipulation and vibration isolation.

Design and Development of Ultrabroadband, High-Gain, and High-Isolation THz MIMO Antenna with a Complementary Split-Ring Resonator Metamaterial.

The need for high-speed communication has created a way to design THz antennas that operate at high frequencies, speeds, and data rates. In this manuscript, a THz MIMO antenna is designed using a metamaterial. The two-port antenna design proposed uses a complementary split-ring resonator patch. The design results are also compared with a simple patch antenna to show the improvement. The design shows a better isolation of 50 dB. A broadband width of 8.3 THz is achieved using this complementary split-ring resonator design. The percentage bandwidth is 90%, showing an ultrabroadband response. The highest gain of 10.34 dB is achieved with this design. Structural parametric optimization is applied to the complementary split-ring resonator MIMO antenna design. The designed antenna is also optimized by applying parametric optimization to different geometrical parameters. The optimized design has a 20 µm ground plane, 14 µm outer ring width, 6 µm inner ring width, and 1.6 µm substrate thickness. The proposed antenna with its broadband width, high gain, and high isolation could be applied in high-speed communication devices.

Full mode-converting transmission between longitudinal and bending waves in plates and beams

Two major challenges are often encountered in wave manipulation involving coupled bending and longitudinal modes. First, the coupling phenomena are generally governed by cubic equations, which are critically complicated for theoretical exploration. Second, there is a significant impedance mismatch between these two modes, which hinders the transmodal energy transferring. In this work, we successfully overcome these challenges, and propose an interference theory that can realize a nearly full mode-converting transmission between bending and longitudinal modes. Specifically, we find an alternative way in which the coupling phenomena can be described using only a portion of the wave characteristics, and solution of the cubic equation is no more required. Besides, we consider locally resonant metamaterials that exhibit extreme anisotropy in effective mass density. The proposed theory consists of four conditions, namely, the interference condition, impedance condition, polarization condition, and supplementary condition. Requirements on the effective material properties are derived from these conditions, and locally resonant metamaterials are designed accordingly. The theory, applicable not only for thin plates, but also for Euler-Bernoulli beams, offers a new way to realize free manipulation of wave energy in elastic systems.

Effect of geometrical parameters and additional mass on the acoustic and vibration control of the bilayer resonant metamaterials

Due to the advantages of lightweight, small size, high stiffness, and adjustable parameters, plate metamaterials have shown great practical application value in the field of acoustic vibration control in engineering. For low-frequency vibration and noise control, an annular slotted bilayer plate metamaterial is designed, which can realize sound insulation and vibration reduction at 100–150 Hz (low-frequency range). By changing the geometric parameters of the annular slotted bilayer plate, the structural parameters of the additional mass, the material parameters, and its distribution position, the acting frequency band is reduced and the band gap of sound insulation and vibration reduction is widened. The integral metamaterial panels of circular and square PA12 were fabricated by 3D printing technology, and then, the acoustic and vibration characteristics were tested in the ZK1030 impedance tube system and Polytec full-field scanning laser vibration measurement system, respectively. The results show that the structure has the best performance by varying the resonant ring thickness of the lattice structure, controlling the wave incidence angle to 0°, and pointing force excitation in the X direction. However, when the mass of the additional mass block is certain, the distribution position of the mass block has less effect. The experimental result was reasonably consistent with the simulation analysis result. This work can provide a reference for the design of bilayer plate acoustic metamaterials with low-frequency broadband acoustic insulation and low-damping vibration based on periodic structures in engineering.

Nonlinear energy localisation in a model of plane metamaterial

Applying the concepts of nonlinear normal modes and limiting phase trajectories introduced by Manevitch in Manevitch (Arch Appl Mech 77:301–312, 2007) to a two-dimensional mass–spring system, the authors propose a generalised method to tune a plane metamaterial and get the desirable resonant behaviour at short wavelengths. Indeed, the account of nonlinear coupling between the oscillators enables the localisation of energy leading the origin of a bandgap at short wavelengths regardless the existence of external disturbances. Moreover, further restrictions on the modes amplitude allow the observation of Fermi–Pasta–Ulam–Tsingou recurrence and super-recurrence in the two-dimensional metamaterial. These findings can open the way to further research in order to improve efficiency and performance of resonant metamaterials.

Lightweight gearbox housing with enhanced vibro-acoustic behavior through the use of locally resonant metamaterials

Mass reduction of automotive components enhances vehicles’ performance and extends their driving range. However, lightweight construction typically leads to noise and vibration issues. Hence, the development of lightweight components must go in tandem with advancements in the field of noise and vibration. This work focuses on the lightweighting of the gearbox housings (GBHs) and on the introduction of vibroacoustic metamaterials to improve their Noise, Vibration, and Harshness (NVH) characteristics. Topology optimization methods were used to reduce the mass of a GBH. Its noise emission was evaluated numerically, before and after the mass reduction. Locally resonant metamaterial (LRM) solutions were applied in the GBH and then tested in numerical simulations. This analysis showed the LRM solutions reduce the emission of noise in the predicted band gaps (BGs), while also providing significant attenuation across the entire frequency spectrum under consideration. The experimental results confirmed the effectiveness of the LRM attenuation concept and the trends observed in the numerical results. Vibration was also attenuated in parts of the GBH where the LRM was not applied. Attenuation of in-plane housing vibration was also observed. The proposed LRM solutions are lightweight, passive and low-cost solutions that can implemented in housings to enhance their NVH characteristics.

Extreme Spatial Dispersion in Nonlocally Resonant Elastic Metamaterials.

To date, the vast majority of architected materials have leveraged two physical principles to control wave behavior, namely, Bragg interference and local resonances. Here, we describe a third path: structures that accommodate a finite number of delocalized zero-energy modes, leading to anomalous dispersion cones that nucleate from extreme spatial dispersion at 0Hz. We explain how to design such zero-energy modes in the context of elasticity and show that many of the landmark wave properties of metamaterials can also be induced at an extremely subwavelength scale by the associated anomalous cones, without suffering from the same bandwidth limitations. We then validate our theory through a combination of simulations and experiments. Finally, we present an inverse design method to produce anomalous cones at desired locations in k space.

All-optical switching of liquid crystals at terahertz frequencies enabled by metamaterials.

Nematic liquid crystals integrated with metallic resonators (metamaterials) are intriguing hybrid systems, which not only offer added optical functionalities, but also promote strong light-matter interactions. In this report, we show with an analytical model that the electric field generated by a conventional oscillator-based terahertz time domain spectrometer is strong enough to induce partial, all-optical switching of nematic liquid crystals in such hybrid systems. Our analysis provides a robust theoretical footing for the mechanism of all-optical nonlinearity of liquid crystals, which was recently hypothesised to explain an anomalous resonance frequency shift in liquid crystal-loaded terahertz metamaterials. The integration of metallic resonators with nematic liquid crystals offers a robust approach to explore optical nonlinearity within such hybrid material systems in the terahertz range; paves the way towards increased efficiency of existing devices; and broadens the range of applications of liquid crystals in the terahertz frequency range.

Reprogrammable acoustic metamaterials for multiband energy harvesting

Acoustic metamaterials are artificial materials that possess the remarkable ability to control and manipulate acoustic waves, which makes them ideal for acoustic energy harvesting. However, the current limitation is that these metamaterials can only effectively harvest energy within a narrow band defined by a single defect mode. To overcome this challenge, a new type of reprogrammable acoustic metamaterial has been developed. This metamaterial incorporates local resonance and magnetic modulation of the structure to enable multiband piezoelectric energy harvesting. The design of triple-band energy localization and regulation involves the utilization of the Bloch theorem and magnetic dipole model. The Bloch theorem is utilized to investigate the propagation of waves within acoustic metamaterials. Electromechanical conversion is achieved through the direct piezoelectric effect of piezoelectric ceramic. Pressure acoustics, solid mechanics, electrostatics and electrical circuit modules are employed to simulate the coupling effects among sound, mechanical and electrostatic fields for acoustic energy harvesting. The magnetic dipole model is employed to determine the magnetic force between the carbon steel cylinders of reprogrammable acoustic metamaterials and the permanent magnet used for magnetic modulation. The structural resonance of the acoustic metamaterials is in charge of band I from 35 Hz to 60 Hz. The local resonance is in charge of band II from 1650 Hz to 2050 Hz. The synergy between the structural resonance and local resonance contributes to band III from 4800 Hz to 5700 Hz with dominance of the structural resonance. The harvested powers of the acoustic metamaterials are 0.10 mW, 0.23 mW and 0.13 mW for different bands. By utilizing reprogrammable magnetic modulation on the structural resonances, the harvested powers for band I and band III experience remarkable enhancements of 655% and 214%, respectively. This breakthrough has the potential to revolutionize the field of acoustic energy harvesting, enabling the harvesting of energy across a wider range of frequencies. We anticipate that the implementation of the multiband acoustic metamaterial energy harvesting wall will expedite the growth of advanced technologies pertaining to acoustic energy localization and self-powered sensing.

Digital coding Fano resonance based on active plasmonic metamaterials.

A novel approach that employs active plasmonic metamaterials to create a digital coding Fano resonator is proposed, to the best of our knowledge. The meta-device consists of three concentric spoof localized surface plasmon (LSP) resonators and three positive-intrinsic-negative (PIN) diodes positioned at three slits located in the middle and inner LSP resonators. Four Fano resonant modes can be independently switched by controlling the biased voltage applied to the three diodes. This provides a means for encoded modulation of multiple Fano resonances in metamaterials, which could have broad applications in fields such as multiway sensing, plasmonic circuits, and switching. We experimentally demonstrate the effectiveness of the proposed approach, which offers promising potential for practical implementation.

3D printing of fiber composite sandwich metamaterial with spiral resonators for attenuation of low-frequency structural vibration

This paper proposes a fiber composite sandwich metamaterial as a stiff structure with a low-frequency band gap. The proposed structure is a locally resonant metamaterial that inhibits the propagation of elastic waves with spiral resonators. The dispersion curves and stiffness of the metamaterial were obtained using the finite element method. The numerical analysis results indicated that the proposed sandwich structure contributes not only to the improvement of the specific stiffness but also to the widening of the band gap. From observations of the band gap boundary modes, an analytical model was developed to derive the lower and upper bound frequencies of the band gap. A metamaterial sample manufactured by 3D printing exhibited a frequency range with low vibration transmissibility, which agreed with the results of the frequency response analysis. The specific bending stiffness and band gap center frequency of the proposed metamaterial were compared with those of existing plate-type metamaterials.

Phononic-subsurface flow stabilization by subwavelength locally resonant metamaterials

The interactions between a solid surface and a fluid flow underlie dynamical processes relevant to air, sea, and land vehicle performance and numerous other technologies. Key among these processes are unstable flow disturbances that contribute to fundamental transformations in the flow field. Precise control of these disturbances is possible by introducing a phononic subsurface (PSub). This comprises locally attaching a finite phononic structure nominally perpendicular to an elastic surface exposed to the flowing fluid. This structure experiences ongoing excitation by an unstable flow mode, or more than one mode, traveling in conjunction with the mean flow. The excitation generates small deformations at the surface that trigger elastic wave propagation within the structure, traveling away from the flow and reflecting at the end of the structure to return to the fluid-structure interface and back into the flow. By targeted tuning of the unit-cell and finite-structure characteristics of the PSub, the returning waves may be devised to resonate and reenter the flow out of phase, leading to significant destructive interference of the continuously incoming flow waves near the surface and subsequently to their attenuation over the spatial extent of the control region. This entire mechanism is passive, responsive, and engineered offline without needing coupled fluid-structure simulations; only the flow instability’s frequency, wavelength, and overall modal characteristics must be known. Disturbance stabilization in a wall-bounded transitional flow leads to delay in laminar-to-turbulent transition and reduction in skin-friction drag. Destabilization is also possible by alternatively designing the PSub to induce constructive interference, which is beneficial for delaying flow separation and enhancing chemical mixing and combustion. In this paper, we present a PSub in the form of a locally resonant elastic metamaterial, designed to operate in the elastic subwavelength regime and hence being significantly shorter in length compared to a phononic-crystal-based PSub. This is enabled by utilizing a sub-hybridization resonance. Using direct numerical simulations of channel flows, both types of PSubs are investigated, and their controlled spatial and energetic influence on the wall-bounded flow behavior is demonstrated and analyzed. We show that the PSub’s effect is spatially localized as intended, with a rapidly diminishing streamwise influence away from its location in the subsurface.

Label-free distinguish proliferative and apoptotic responses of glioma cells with terahertz metamaterials

Glioma exhibits various sensitivities to the same treatment due to its high invasiveness and heterogeneity, which are typically assessed by the proliferative and apoptotic cell activities. Currently, classical label methods for cell proliferation and apoptosis detection are destructive and time-consuming, and spectral and electrochemical technologies without label can hardly distinguish the proliferation and apoptosis responses. Here, a label-free approach to simultaneously detect the proliferative and apoptotic features of glioma cells with terahertz metamaterials is reported for the first time. The biosensor comprises periodic metamaterial resonators, whose frequency shifts in ∆f as the cell number and state vary. Three glioma cell lines under the most sophisticated therapies, i.e., chemotherapy and radiotherapy, are investigated. Various frequency-shift responses are observed for the live and apoptotic cells, revealing different refractive indices for them. By using standard biological assays to identify cell numbers and proliferation and apoptosis rates, the relation between ∆f and the numbers of live and apoptotic cells is fitted, which consequently reveals the relation of ∆f with respect to both proliferation and apoptosis rates unprecedentedly. This work paves a new way to study the proliferative and apoptotic responses of tumor cells, showing promising potential to guide individualized tumor treatments fast and label-free.

Triple-Band Surface Plasmon Resonance Metamaterial Absorber Based on Open-Ended Prohibited Sign Type Monolayer Graphene.

This paper introduces a novel metamaterial absorber based on surface plasmon resonance (SPR). The absorber is capable of triple-mode perfect absorption, polarization independence, incident angle insensitivity, tunability, high sensitivity, and a high figure of merit (FOM). The structure of the absorber consists of a sandwiched stack: a top layer of single-layer graphene array with an open-ended prohibited sign type (OPST) pattern, a middle layer of thicker SiO2, and a bottom layer of the gold metal mirror (Au). The simulation of COMSOL software suggests it achieves perfect absorption at frequencies of fI = 4.04 THz, fII = 6.76 THz, and fIII = 9.40 THz, with absorption peaks of 99.404%, 99.353%, and 99.146%, respectively. These three resonant frequencies and corresponding absorption rates can be regulated by controlling the patterned graphene's geometric parameters or just adjusting the Fermi level (EF). Additionally, when the incident angle changes between 0~50°, the absorption peaks still reach 99% regardless of the kind of polarization. Finally, to test its refractive index sensing performance, this paper calculates the results of the structure under different environments which demonstrate maximum sensitivities in three modes: SI = 0.875 THz/RIU, SII = 1.250 THz/RIU, and SIII = 2.000 THz/RIU. The FOM can reach FOMI = 3.74 RIU-1, FOMII = 6.08 RIU-1, and FOMIII = 9.58 RIU-1. In conclusion, we provide a new approach for designing a tunable multi-band SPR metamaterial absorber with potential applications in photodetectors, active optoelectronic devices, and chemical sensors.

실시간 상태-공간 식별 기반 제어기를 이용한 유한 국부공진 메타물질 평판의 적응형 진동 저감

To improve the internal sound quality of an electric vehicle, the noises (tire and road noises), vibration, and discomfort should be reduced effectively. Compared to the conventional damping materials, the locally resonant metamaterial is advantageous in terms of reducing the vibration in the low frequency band and reducing the weight through a stop band, where vibration is not transmitted. However, the locally resonant metamaterial installed in a finite structure fails to form an ideal stop band. Additionally, there is a problem of occurrence vibration mode at an arbitrary frequency. Accordingly, there is a need for an active vibration control method capable of learning and actively reducing the vibration modes occurring at arbitrary frequencies within the stop band in real-time. In this study, a real-time state-space identification-based active vibration control method was proposed to reduce the vibration modes occurring at arbitrary frequencies within the stationary band of local resonance metamaterials. The active vibration control method proposed in this study, combined with the existing passive vibration reduction method, can be utilized to effectively reduce the vibration for random disturbance of a fluctuating system.