Search

Engineered subsurface structures inspired by phononic materials have shown favorable capabilities in flow control. Current efforts rely on tuning a structural resonance to the frequency of an unstable fluid mode, causing the deformations of the interfacing solid to destructively interfere with a wave-like flow instability. Although promising, the technique is most effective at targeting a single frequency mode with high-Q resonance. Additionally, several studies have shown the reduction in the perturbation energy to be spatially localized to the flow region above the subsurface strip, with a severely worsening effect downstream. Motivated by a desire to overcome these limitations, we present a different approach to methodically extract an undesirable pressure disturbance from a fluid column in a manner that capitalizes on the broad frequency range of a phononic bandgap, with the goal of permanently confining the perturbation energy within the subsurface structure. An acoustic diode (AD), i.e., a unidirectional transmitter of mechanical energy, comprised of a bi-layered phononic crystal and an auxiliary medium, interacts with a fluid cavity and provides a terminal energy sink. Two distinct ADs are presented that demonstrate active (time-variant) and passive (strain-dependent) paths to concept realization. The AD's performance is described in terms of the time-transient energy distribution in the fluid and the interacting structure, as well as spatial wave profiles at critical time instants. The results show the system's ability to achieve robust extraction of undesirable fluid oscillations with minimal residual energy. The concept is then tested in a fully developed plane channel flow with a superimposed perturbation, demonstrating the sustained nature of the subsurface AD's energy trapping mechanism in addition to its ability to induce downstream attenuation. [ABSTRACT FROM AUTHOR]

The active tuning of the bandgaps induced by the acoustic metamaterials has sparked significant interest among researchers. It opens up possibilities for programmable, multifunctional acoustic meta-devices. The static design of acoustic metamaterials, however, has limited automation capabilities, particularly for controlling sound propagation through the elastic solids. Designing acoustic metamaterials with fluid as the host medium, specifically air, significantly reduces these constraints. Given this observation, the present work demonstrates a novel design technique that transforms a Phononic Crystal (PnC) into an Active Acoustic Meta-device (AAMD). The designed AAMD has been demonstrated as programmable and multi-functional. It functions as an acoustic barrier over around 94% of the applied frequency sweep (a.f.s)., 300–3500 Hz. As an acoustic transmitter, it magnifies acoustic energy over around 50% of the a.f.s. Similarly, it functions as an acoustic switch over 100% of the a.f.s. This metadevice distinguishes itself by solely utilizing a two-phase material system and employing basic design elements, rather than common resonating elements, such as Helmholtz resonators or softer coatings. [ABSTRACT FROM AUTHOR]

A deep learning neural network-assisted design strategy for programmable piezoelectric phononic crystal (PnC) beams with shunt circuits is proposed. The feasibility of integrating deep learning into the design of tunable PnCs to achieve real-time vibration isolation is demonstrated through numerical examples. The influence of shunt circuits (capacitance) on bandgaps of piezoelectric PnCs is studied by finite element (FE) simulations. The results show that the bandgap frequency and range vary with the capacitance and electrode length. Moreover, incorporating supercell structures introduces an additional bandgap, significantly expanding the tunable range of the bandgap and demonstrating that shunt circuit modifications can tailor the frequency and width of the bandgap. A suite of deep learning neural network (NN) algorithms is developed for predicting bandgaps and inversely designing PnC parameters, greatly accelerating the bandgap calculation and enabling faster inverse design than existing models. The accuracy of the NN algorithms is verified by comparing their predictions with those from FE simulations. The combination of designed PnC beams and deep learning NNs enables real-time vibration reduction and isolation. This design strategy is successfully validated in a practical scenario involving real-time vibration isolation of train rails. [ABSTRACT FROM AUTHOR]

This work presents a high-sensitivity solution sensor based on a phoxonic crystal nanobeam with lateral fins. The fins improve the stability of the suspended nanobeam and its detection performance is unaffected. Acoustic–optic dual-mode cross-detection improves the detection accuracy over the single-mode method. The acoustic and optical energies are concentrated in the defect and slot regions due to the combination of the gradient cavity and slot, which enhances the acoustic–optic interaction with the object to be measured, improving the detection sensitivity. Using the mode bandgaps of photonic and phononic crystals, the sensing characteristics are investigated using the finite element method. The impact of various concentrations on the transmission spectra of optical electromagnetic waves and acoustic elastic waves is investigated. The maximum sensitivity is 2149.5 kHz/ms−1, with Q of over 105 in the acoustic mode and 457.1 nm/RIU in the optical mode. The proposed nanobeam cavity with lateral fins can be used to realize miniaturized multi-mode acoustic–optic sensors. It also provides mechanical support, thermal transport, and channels for lateral carrier injection for the suspended nanobeam. [ABSTRACT FROM AUTHOR]

In this numerical study, we propose dual-modulated topological pillared phononic crystal (PnC) plates and demonstrate their application in achieving frequency-selective waveguiding of Lamb-wave valley-edge states. We show that both the radius and the height of the pillars in the honeycomb unit cell can be varied, allowing a generalized parameter space to obtain the complete topological bandgaps and two groups of distinct valley Hall phases for designing topological waveguides operating in different frequency ranges. Accordingly, we construct different types of phase domain walls to support valley-edge states using the dual-modulated PnC plates with a lattice constant of 2000 μm and with topological bandgaps opened around the Dirac cone frequency of 426 kHz. The numerical results show that the valley-edge states emerge to cover different frequency ranges and exhibit robust backscattering immunity when propagating along zigzag paths with sharp corners. Furthermore, the transport path of the valley-edge states can be designed to be highly dependent on the operating frequency in different domain walls. Consequently, we design a straight waveguide and three multichannel waveguides to demonstrate frequency-dependent switchable transmission and selective channeling of valley-edge states, respectively. The results of this study pave the way for the development and optimization of topological acoustic circuits using the generalized parameter space approaches and are expected to find promising applications in frequency-controlled and signal-division devices. [ABSTRACT FROM AUTHOR]

A hydrogen sensor is created on the basis of an acoustic topological material with a coiled structure. Compared to traditional hydrogen sensors, the sensor does not possess a sensitive layer and works with the shift of a topological interface state induced by hydrogen. The sensor is composed of two phononic crystals with distinct topological characteristics, and an interface state is achieved at the interface of both phononic crystals. When hydrogen is introduced into the sensor, the density and the sound velocity of the gas in the sensor change, which shifts the frequency of the interface state. Thus, the concentration of hydrogen can be obtained by measuring the frequency shift of the interface state. Due to the absence of a sensitive layer, the sensor operates without a chemical sorption process, and the performance of the sensor is marginally influenced by working conditions, temperature, and humidity. Theoretical analysis, numerical simulations, and experimental results show that in different background gases, synthetic air, nitrogen, and argon, the sensor exhibits relative sensitivities of 0.50, 0.50, and 0.37, which do not change with the working conditions. Additionally, the sensor possesses a rapid response, a good linearity and robustness, and a long lifespan. Furthermore, the sensor is designed based on a coiled structure, which considerably improves the space utilization and decreases the bulk. [ABSTRACT FROM AUTHOR]

Band structure and Dirac degeneracy are essential features of sonic crystals/acoustic metamaterials to achieve advanced control of exciting wave effects. In this work, we explore a deep learning approach for the design of phononic crystals with desired dispersion. A plane wave expansion method is utilized to establish the dataset relation between the structural parameters and the energy band features. Subsequently, a multilayer perceptron model trained using the dataset can yield accurate predictions of wave behavior. Based on the trained model, we further impose a re-learning process around a targeted frequency, by which Dirac degeneracy and double Dirac degeneracy can be embedded into the band structures. Our study enables the deep learning approach as a reliable design strategy for Dirac structures/metamaterials, opening up the possibilities for intriguing wave physics associated with Dirac cone. [ABSTRACT FROM AUTHOR]

Based on the quantum valley Hall effect analogy, this work proposes a phononic crystal plate with ligament-type beams to obtain the topological valley transmission of elastic waves. A pure Bragg degenerate state appears in the high-frequency region with a resonator introduced. By rotating the central scatterer and the beams, the mirror symmetry is broken to form a topological bandgap. Subsequently, this work finds that two selective edge states also appear beside the commonly non-trivial crossing edge states in the topological bandgap by calculating the projected band and eigenvalue spectrum of the supercell with different valley Hall phases phononic crystals. Their appearance is due to band separation of the topological edge states caused by an increase in the rotation angle. Both selective edge states can transmit topologically in specific paths. They will help further to broaden the width of the frequency band of topological transmission. Besides, an elastic wave splitter is designed and demonstrated numerically, which can form two channels and three channels in different frequency bands. With the topological selective edge state disappearing, a topological corner state exists in the edge bandgap. This work provides a theoretical reference for practical applications of broadband elastic wave topological transmission and elastic energy trapping. [ABSTRACT FROM AUTHOR]

We present experimental demonstration and modeling of mechanical wave propagation in a quasi-one-dimensional (quasi-1D) phononic crystal (PnC) waveguide (WG) constructed from a periodic array of single-crystal cubic-silicon carbide (3C-SiC) coupled micromechanical resonators, with an exceptional dynamic range exceeding 92 dB. The PnC design comprises 50 periodic cells, enabling the propagation of flexural mechanical waves in high-frequency and very-high-frequency bands, featuring a broad PnC bandgap spanning approximately 24–27.5 MHz. Furthermore, the 3C-SiC PnC WG exhibits excellent characteristics, including a high group velocity of 350 m/s and a low transmission loss of 0.69 dB/mm, enabling efficient guidance and support for mechanical waves across extended distances before reaching the noise level of the device. These attributes of the PnC WG, as demonstrated in this study, may open possibilities for the development of device platforms with applications in on-chip signal processing, sensing, and quantum transducer technologies. [ABSTRACT FROM AUTHOR]

Recently, the mode conversion of elastic waves has attracted much attention, due to its scientific significance and potential applications. The applications based on the high mode conversion efficiency were also explored in many fields. However, because of the complexity of elastic waves, the existing structures for the high efficient conversion of elastic waves are relatively complicated, and there are also some limitations in the practical design. Here, we report the extraordinary mode conversion of elastic waves through asymmetric brass plates partitioned by subwavelength cuts. It is demonstrated that high efficiencies (90%) and one-way conversions between transversal waves and longitudinal waves are achieved by the structured solid plate at the resonant frequency, which leads to the striking unidirectional transmission of elastic waves. Analyzing the resonant fields demonstrates that the intrinsic modes within the individual pieces derived by the cuts are responsible for this abnormal wave conversion. The simple scheme for wave conversion presented here may have potential applications, such as non-invasive flow sensing. [ABSTRACT FROM AUTHOR]

This study illustrates the successful achievement of tunable defect bands in one-dimensional defective phononic crystals (PnCs) through the incorporation of piezoelectric defects with synthetic negative capacitances (SNCs) for the first time. The efficacy of SNCs in creating tunable bandpass filters across a broad frequency range is thoroughly examined using the proposed analytical and numerical models. A newly developed electroelastically coupled transfer matrix that incorporates SNCs is presented, considering either series or parallel connection between bimorph piezoelectric elements. Defect band and transmittance analyses are conducted using the transfer matrix and S-parameter methods. Two key findings emerge from this investigation. First, when the total equivalent capacitance of the bimorph piezoelectric elements and SNC becomes zero, the defect band representing the point-symmetric defect-mode shape can be customized throughout the entire phononic bandgap. Second, the constant transmittance value, resembling short-circuit conditions, highlights the remarkable ability of SNCs to tune defect bands without energy dissipation, paving the way for fully tunable bandpass filters. To propel this research forward, future investigations could explore expanding the design space with double defects, adopting enhanced modeling techniques to account for lateral and shear effects, developing a control algorithm for the automatic optimization of SNC values in actively tunable bandpass filters, and incorporating artificial intelligence into design methods for piezoelectric defects with electrical connections. [ABSTRACT FROM AUTHOR]

This paper presents the design of a single-phase solid phononic crystal (PnC) structure featuring a regular hexagonal perforation pattern. The structure manifests three negative refraction bands, encompassing one for transverse waves and two for longitudinal waves, thereby enabling simultaneous control of shear and longitudinal waves. Due to the high symmetry of the triangular lattice, the equal frequency curves corresponding to the negative refraction band approach circular shapes, suggesting a nearly isotropic negative refraction effect. This negative refraction effect is achieved through specific mass resonance modes closely related to the porous structure designed in this paper. Initially, we analyze the band structure of the PnC, followed by designing the PnC plate structure to achieve negative refraction control for transverse waves at a frequency of 32.4 kHz, with a negative refraction index of −1. Additionally, negative refraction control for longitudinal waves is attained at frequencies of 44 and 64.54 kHz. Subsequently, we scrutinize the influence of various conditions on negative refraction, including different structural parameters, incident angles, and operating frequencies, while verifying the robustness of the designed phonon crystal structure. Leveraging the negative refraction characteristics of the structure, we construct an elastic wave lens to achieve perfect imaging of shear and longitudinal waves. Finally, employing finite element simulation and analyzing focusing imaging characteristics with different source positions, we validate that the results closely align with theoretical expectations. The solid PnC structure designed in this study holds significant potential for applications in the fields of elastic wave imaging. [ABSTRACT FROM AUTHOR]

Inspired by the emerging field of twistronics, moiré photonic structures have attracted great interest. In this paper, we introduce the concept of the moiré Kagome lattice (MKL), which arises from the overlapping of a Kagome lattice at a commensurable angle of 38.211°. MKL exhibits a significantly broader main photonic bandgap (PBG) when compared to the traditional Kagome lattice. Through numerical simulations, we delved into the adjustable properties of the PBG of MKL by varying lattice parameters, including filling factors and materials. Meanwhile, we also observed the presence of photonic flatbands within the MKL structure. Specifically, the emergence of a super flat isolated flatband aids in achieving single-mode omnidirectional lasers and enhancing the omnidirectional electromagnetic interaction of materials, thereby expanding the applications of moiré photonic crystals. [ABSTRACT FROM AUTHOR]

Diffraction-free beams with large depth-of-field have a lot of potential in the field of acoustics, such as imaging, sensing, and particle manipulation. In this study, an acoustic Bessel-like beam is produced using an axicon-sonic crystal lens. The sonic crystal is created using cylindrical glass rods arranged in a triangular shape with a centered square lattice configuration. The numerical simulation between 4 and 8 kHz indicates that the axicon-sonic crystal converts the plane acoustic wave into a Bessel-like beam. The analysis of the beam indicates that the depth of field of this beam depends on the size and periodicity (lattice parameter) of the sonic crystal. The axicon lens also displays variable focal lengths at different frequencies. A graded index layer was implemented to mitigate the reflection caused by the significant impedance mismatch. Experimental validation of acoustic Bessel-like beam formation is also reported for the working frequencies. At 8 kHz, the measured range to the 50 % on-axis intensity was 34 λ , while the focus width at the same frequency was measured to be 2 λ. The integration of three distinct design strategies—axicon shape, sonic crystal, and graded index—expands the possibilities for sound focusing applications. [ABSTRACT FROM AUTHOR]

AbstractIn this paper, a novel one-dimensional (1D) phononic crystal fiber with conical entrance has been proposed for energy harvesting application. The cladding part of the phononic fiber is 1D phononic crystal which is included 4 layers of steel and 3 layers of epoxy resin materials. Also, an epoxy resin rod has been considered as core. The energy harvesting working frequency is 50 kHz, so in the first step, we focus on designing the 1D phononic crystal. Next, optimized 1D phononic crystal has been selected as phononic crystal cladding. The most important parameter to adjust the working frequency of phononic fiber is the radius of core. For obtaining the electrical output, a piezoelectric film is considered at the end of phononic crystal fiber. A conical entrance is designed to couple the acoustic wave from environment to core region. Simulation of structure has been done by finite element method. Achieved results show that incident acoustic waves can confine in the core region. The comparison of output voltage with the bare case shows a 70 times enhancement for the proposed structure. [ABSTRACT FROM AUTHOR]

Defective phononic crystals (PnCs) have enabled spatial localization and quantitative amplification of elastic wave energy. Most previous research has focused on applications such as narrow-bandpass filters, ultrasonic sensors, and piezoelectric energy harvesters, typically operating under the assumption of an external elastic wave incidence. Recently, a novel approach that uses defective PnCs as ultrasonic actuators to generate amplified waves has emerged. However, the existing studies are limited to the generation of either longitudinal or bending waves, with no research addressing the concurrent generation of both. Hence, this paper proposes a straightforward methodology for the concurrent generation and amplification of both wave types utilizing defect modes at independent defect-band frequencies. Bimorph piezoelectric elements are attached to the defect, with each element connected to independent external voltage sources. By precisely adjusting the magnitude and temporal phase differences between the voltage sources, concurrently amplified wave generation is achieved. The paper highlights the advantages of the proposed analytical model. This model is both computationally time-efficient and accurate, in comparison with the COMSOL simulation results. For instance, in case studies, the analytical model reduces the computational time from one hour to mere seconds, while maintaining acceptable error rates of 1% in peak frequencies. This concurrent wave-generation methodology opens new avenues for applications in rotating machinery fault diagnosis, structural health monitoring, and medical imaging. [ABSTRACT FROM AUTHOR]

Although the theoretical basis for surface acoustic wave gyroscopes (SAWGs) was first proposed in 1980, their design concepts are still under development. Nevertheless, these sensors are of a great interest in the potential market owing to their exceptional shock resistance, small size, low power consumption, and simple manufacturing process that ensures low cost. This paper aims to conscientiously investigate the ideas that have been proposed over the past decade in this area and evaluate the potential development required to bring SAWGs to market. It should be of interest for researchers in the field who might have missed some useful solutions that could be a missing piece in their own design, or for young researchers to inspire their creativity and open new research on the topic. Additionally, since some of the reviewed SAWG design concepts are based on a combination of several physical principles (for example, optical measurements), researchers from other fields may find useful solutions for incorporating surface acoustic wave techniques into their device concepts. [ABSTRACT FROM AUTHOR]

This paper reverse-design phononic crystals with band gaps within a targeted frequency band using the trained conditional variational autoencoder (CVAE) and further studies the vibro-acoustic characteristics of a composite sandwich plate with a phononic crystal panel as the core layer. Firstly, a matrix composed of 0 s and 1 s, representing scatterers and substrates, is randomly generated by MATLAB to represent two-dimensional phononic crystals. The three-dimensional phononic crystals are obtained by stretching the two-dimensional phononic crystals along the average direction, and COMSOL Multiphysics is used to calculate the band gap. In order to maximize the production of phononic crystals with a band gap distribution, the convolutional neural network is trained to predict whether the generated phononic crystals have band gaps. Finally, using data on the structures of phononic crystals and their band gap distributions, the CVAE is trained to achieve the reverse design of artificial periodic structures based on the target band gap. To verify the effectiveness of the structures obtained through the reverse design method on vibration and noise reduction, the submerged vibro-acoustic characteristics of a composite sandwich plate are studied. The plate consists of a phononic crystal panel and carbon fiber panels. The model of the composite sandwich plate is fabricated, and its submerged vibro-acoustic characteristics are tested and compared with numerical results. Finally, the submerged vibro-acoustic response levels of composite sandwich plates with phononic crystal panels and honeycomb panels as core layers are compared using numerical methods. This comparison assesses the phononic crystal panel's vibration and noise reduction effects. [ABSTRACT FROM AUTHOR]

The phononic crystals composed of soft materials have received extensive attention owing to the extraordinary behavior when undergoing large deformations, making it possible to provide tunable band gaps actively. However, the inverse designs of them mainly rely on the gradient-driven or gradient-free optimization schemes, which require sensitivity analysis or cause time-consuming, lacking intelligence and flexibility. To this end, a deep learning-based framework composed of a conditional variational autoencoder and multilayer perceptron is proposed to discover the mapping relation from the band gaps to the topology layout applied with prestress. The nonlinear superelastic neo-Hookean model is employed to describe the constitutive characteristics, based on which the band structures are obtained via the transfer matrix method accompanied with Bloch theory. The results show that the proposed data-driven approach can efficiently and rapidly generate multiple candidates applied with predicted prestress. The band gaps are in accord with each other and also consistent with the prescribed targets, verifying the accuracy and flexibility simultaneously. Furthermore, based on the generalization performance, the design space is deeply exploited to obtain desired soft structures whose stop bands are characterized by wider bandwidth, lower location, and enhanced wave attenuation performance. [ABSTRACT FROM AUTHOR]

AbstractThe elastic wave band gap (BG) property of locally resonant phononic crystal (LRPC) enables it to control and attenuate the propagation of elastic waves in its internal structure in the BG frequency range. In particular, it has unique advantages in obtaining low-frequency BG and can be used for the control and attenuation of low-frequency vibration. Therefore, the LRPC is of great significance in the field of low-frequency vibration reduction and has broad application value and prospect. However, the LRPC has the defects of narrow BG width and only one BG, which makes it limited in engineering application. In response to the problems of narrow BG width and only one BG in traditional LRPC Euler beams, this paper establishes a novel phononic-like crystal (PLC) Euler beam model that can open up multi-frequency and low-frequency vibration reduction BGs. The PLC Euler beam model considers the non rigidity of the contact interface between the wrapping layer and the scatterer and matrix, the foundation constraint effect, and the damping characteristics of the wrapping layer material. The vibration reduction BG characteristics of the PLC Euler beam are studied through theoretical calculations and analysis. Firstly, the improved transfer matrix method (ITMM) is derived for calculating the band structure of the PLC Euler beam, and the results are compared and verified with those obtained from the finite element method (FEM). Secondly, the spectral element method (SEM) is derived for calculating the frequency response function (FRF) of the PLC Euler beam, and to evaluate its attenuation effect on vibration elastic waves. The theoretical calculation results show that the PLC Euler beam opens up 6 low-frequency vibration reduction BGs, exhibiting good attenuation effects on vibrational elastic waves within the BG frequency range, with the maximum attenuation value at the BG starting frequency. The novel PLC Euler beam has a broad prospect in controlling and attenuating low-frequency and multi-frequency vibrations, and its design idea has a unique novelty, which provides theoretical support and design idea for broadening the BG width and number of LRPC Euler beam structures, and provides theoretical methods and ideas for designing and studying LRPC with low-frequency and multi-frequency BGs. [ABSTRACT FROM AUTHOR]

Surface acoustic waves are commonly used in a variety of radio-frequency electrical devices as a result of their operation at high frequencies and robust nature. For devices based on Rayleigh-like plane waves, functionality is based on the fact that the Rayleigh wave mode is confined at the solid–air interface. However, to create advanced functionality through the use of phononic crystal structures, standard cylindrical inclusions have been shown to couple Rayleigh modes to the shear horizontal bulk modes and provide a significant pathway to energy loss. We introduce alternative inclusion shapes with a reduced two-fold symmetry that lowers the speed of the Rayleigh-like surface acoustic wave to below that of the shear horizontal mode. With an eigenfrequency below the sound line, the mode is confined to the surface with limited coupling and loss to the bulk. Based on these inclusions, an acoustic waveguide design is proposed, which demonstrates a strong confinement of wave energy both at the surface and within the waveguide. [ABSTRACT FROM AUTHOR]

The goal of this work is to determine the widest bandgaps possible for Phononic Crystals (PnCs) operating in the MHz–GHz frequency range by using the Planes Approximation Method (PAM). MHz–GHz PnCs have micro/nanoscale features which must be fabricated in a cleanroom with cleanroom compatible materials. 1D and 2D simulations are performed, using PAM, for bimaterial (two-material) phononic crystals for 41 cleanroom compatible materials to determine the widest bandgaps. 1D results yield a monotonic, characteristic curve demonstrating a logarithmic relationship between the gap/midgap ratio and normalized impedance with an R2 value of 0.965. 2D simulations with circular inclusions on a square lattice demonstrate an increasing linear trend for the gap/midgap ratio and normalized impedance. The interplay between the Γ X and Γ M directions cause deviations from monotonicity. [ABSTRACT FROM AUTHOR]

Energy dissipation through support structures is one of the dominant loss mechanisms in MEMS resonators, which results in a very low quality (Q) factor. This paper aims to propose a one-dimensional phononic crystal (PnC) structure, namely a compound leaf-shaped phononic crystal (PnC) strip (TYPE_PROP), as anchor tethers to boost the anchor quality factor ( Q anchor ) of a thin-film aluminium nitride (AlN)-on-silicon (Si) MEMS resonator. Thus, its Q can achieve a superior value. The operating frequency and mode of the resonator are 123.49 MHz and a length extensional (LE) mode, respectively. This frequency falls into the band gap frequency range of 52 MHz of the TYPE_PROP. The Q anchor of the resonator with unit cell number variation of the TYPE_PROP tether is studied. From these investigations, the effectiveness of the tether in reducing/eliminating the anchor energy loss is evaluated. Furthermore, this Q anchor is also compared to the same resonator structure with two conventional tether types. Additionally, the variation of the band gaps' properties versus the dimensional parameters of the TYPE_PROP are also evaluated. The COMSOL Multiphysics platform based numerical results demonstrate that the Q anchor of the resonator with the TYPE_PROP based tethers achieves superior values compared to its counterparts. Specifically, this value is about 5.42 × 10 12 and 23.74 times higher than that of the TYPE_CON1 and TYPE_CON2, respectively. The Q anchor improvement of the LE mode MEMS resonator using the TYPE_PROP achieves higher values than that using two conventional tether configurations. [ABSTRACT FROM AUTHOR]

This work presents a novel design that uses a fluid–fluid 2D phononic crystal ring resonator (PnC-RR) as a half adder and half subtractor. Based on acoustic waveguides and a crystal ring resonators cavity operating at a single frequency of 45.1 kHz, the suggested Half Adder/Half Subtractor construction is presented. With a rectangular mercury foundation and cylindrical water rods, a square lattice is used to build the two-dimensional structure. Performance parameters such as Amplitude Modulation, Contrast Ratio, and Extinction Ratio lend validity to the design. Comsol Multiphysics is used for all related designs and simulations. In phononic integrated circuits utilized in aquatic and medical applications, the design could be crucial. [ABSTRACT FROM AUTHOR]

Resonant acoustic band gap materials have steered a new sensing technology era. This study is presented to investigate of the one-dimensional (1D) phononic crystals (PnCs), involving periodic, as well as quasi-periodic 1D layered PnCs represented as a highly sensitive biosensor to detect and monitor the quality of milk. In this regard, the numerical findings show that the examined periodic PnCs structure outperformed the quasi-periodic structure. In particular, it provides a wider phononic band gap and greater sensitivity as well. In addition, the quasi-periodic design (especially Fibonacci sequence S4) introduces multiple resonance peaks via transmission spectra, which may lead to some conflicts during the detection process. The findings reveal that the frequency of the resonant peak can effectively change with varied milk solution concentrations and temperatures. The optimized sensor is capable of differentiating between concentrations ranging between 0 and 50 % with a 10 % step, and it can also differentiate between temperatures, which range between 5 °C and 50 °C. This makes it ideal for precise detection of other liquids and solutions. The sensor performs efficiently for all milk solution concentrations. Here, the findings demonstrated that the examined defective PnC structure exhibited the most favorable sensitivity of the value of 94.34 MHz, so it showed the highest sensitivity when varying milk concentrations. In addition, the configurated sensor provided high QF and FOM values of 3,853.645161 and 157.42, respectively. On the other hand, the sensor performs very well for all temperatures of the milk solution. As such, the S4 quasi-periodic structure is characterized as the optimal sensor structure when varying temperatures, introducing a sensitivity of 4.78 MHz/°C, QF of 4,278.521, and FOM of 7.48 °C−1. [ABSTRACT FROM AUTHOR]

In this article, the concept of topological rainbow is introduced into the plate‐mode waves system of 1D phononic crystal slabs, achieving adjustable topological elastic rainbow trapping by employing gradient‐tuned Su–Schrieffer–Heeger (SSH) structures. First, based on the classical SSH model, a phononic crystal slab composed of steel and aluminum is set up, and the band structure of plate‐mode waves is studied using the finite‐element method. Band inversion can be induced by changing the height of the steel in the unit cell, leading to topological phase transitions. Then, phononic crystals with different topological properties are connected to form a phononic crystal slab, realizing topological interface states. Furthermore, a sandwich‐like ultrathin structure is constructed to couple the adjacent two topological interface states. Finally, a 1D alternating SSH structure of phononic crystal slab is designed under gradient structural parameters, and based on eigenfrequency and full‐wave simulation, adjustable topological rainbow trapping based on coupled interface states is achieved. The designed device can trap wide frequencies exceeding 15 kHz, providing more possibilities for the design of elastic‐energy‐harvesting devices. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Dalian University of Technology / Dalian Ligong Daxue Xuebao is the property of Journal of Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: Fluid-conveying pipeline systems, widely used in ocean engineering, aerospace, oil and gas energy transmission, and nuclear steam supply systems, transport fluids to transfer energy, momentum, and mass. However, these systems are prone to uncontrolled vibrations and dynamic instability due to various excitations. Reducing low-frequency broadband vibrations in pipeline systems remains a challenging work for common vibration control techniques. Methods: The bandgap characteristics of emerging phononic crystals (PCs) and acoustic metamaterials (AMs) in the field of condensed matter physics can effectively manipulate the propagation of elastic and sound waves in fluid-conveying pipelines, providing new methods for the low-frequency vibration reduction design of fluid-conveying pipeline systems. Results: This paper provides an overview of traditional vibration reduction methods for pipeline systems, including passive, active, and semi-active control techniques. Based on the bandgap characteristics of PCs and AMs, combined with material and structural optimization , nonlinear effects, and active control methods, a systematic classification and summary were conducted. With a focus on the application of these technologies in low-frequency broadband vibration reduction of pipelines. Conclusion: This paper provides a comprehensive literature review of the development and application of PCs and AMs in pipeline vibration control systems. Analyzed the challenges currently faced in development and provided prospects for future research directions in this area. [ABSTRACT FROM AUTHOR]

The method of reverberation-ray matrix (MRRM) is modified for the dynamic response analysis of beam structures with rigid components. The wave expressions for the beam structures are derived based on the Timoshenko beam theory, and the MRRM formulations are obtained through the compatibility conditions of displacements and joint coupling equations by considering the effects of rigid components. An application of this method is considered in the context of a phononic crystal with spring-mass-like resonators. The proposed resonant unit consists of a large mass-like central component connected to thin beams that serve as springs. The large central component can be approximated as a rigid body. Using the MRRM and the finite element method (FEM), the band diagrams and the transmission spectrums are calculated. The innovative cell offers the advantage of producing lower and wider bandgaps when compared to traditional lattice structures. The accuracy of the MRRM is verified with the FEM. The current research provides a vibration analysis approach for beam structures with rigid components and the analysis of phononic crystals serves as a reference for structural design. [ABSTRACT FROM AUTHOR]

This work introduces various designs of phononic crystals (PnCs), referred to as topological phononic crystals (TPnCs), as novel, stable, and high-performance sensing tools. Meanwhile, we introduce the concept of the topological edge state to address the discrepancies between theoretical predictions and experimental results of PnC sensors. Consequently, the design of a PnC sensor structure that maintains high stability amidst fluctuations in layer manufacturing and deformations during construction represents the mainstay of our study. Notably, the numerical findings demonstrate the stability of the proposed sensor in the presence of various geometric changes. In addition, we assess the effectiveness of several periodic PnC designs in sensing the physical properties of fluids, specifically alcohols like butanol. Accordingly, temperature sensing of butanol is conducted over a wide range (170°C–270°C) by monitoring the displacement of Fano resonance modes. In this regard, the proposed PnC structure demonstrates an impressive sensitivity of 119.23 kHz/°C. Furthermore, our design achieves a high-quality factor and figure of merit of 378.23 and 1.085, respectively, across the temperature range of 170°C–230°C. These outcomes are promising for the development of ultrasensitive thermal sensors. Ultimately, our research provides valuable insights into the creation of highly sensitive and stable temperature sensors suitable for a range of industrial applications. [ABSTRACT FROM AUTHOR]

There is an increasing interest in the study of metamaterials and periodic materials across disciplines. These are anisotropic and their properties present directionality. For example, the wave speed depends on the propagation direction. Furthermore, they are heterogeneous, and their directionality depends on their spectra. Common approaches to describe anisotropy have been used in the large-wavelength approximation corresponding to static properties. Here we present an anisotropy measure based on the dynamic behavior. It receives dispersion surfaces from Bloch analyses and outputs a curve/surface with bulk directionality encoded on it. We present results for elastodynamics, but it is applicable to other phenomena. [ABSTRACT FROM AUTHOR]

Pneumatic manipulation has the advantages of low cost, lightweight design, fast response, and ease of integration. However, its application in the field of phononic crystals remains limited. Inspired by pneumatic soft robots, this article proposes a pneumatic soft phononic crystal arranged in a square lattice, incorporating four pneumatic actuators within the scatterer. By manipulating air pressure, the bandgap can be effectively opened and closed. The finite element analysis is employed to examine the deformation and bandgaps of the pneumatic soft phononic crystal under varying air pressures. Moreover, the effect of the scatterer's rotation angle on the bandgap evolution in the phononic crystal is parametrically investigated. The results show that varying both the volume and the rotation angle of the scatterer can achieve bandgap opening, closing, and tuning. The proposed phononic crystal presents obvious practical applications and provides important insights for the design of soft‐tunable acoustic devices. [ABSTRACT FROM AUTHOR]

AbstractAs a new kind of artificial composite material, locally resonant phononic crystal (LRPC) can attenuate and suppress the propagation of elastic waves in certain frequency range, which has a broad application prospect and value in the field of vibration and noise control. The traditional LRPC can only open one band gap (BG), but the vibration and noise in practical engineering are often multi-band, so the traditional LRPC cannot effectively cover the target frequency range, and the efficiency of vibration and noise reduction is greatly limited. In response to the shortcomings of traditional LRPC, this paper designs a novel locally resonant phononic crystal with multiple primitive cell combination structure (LRPCWMPCCS), which is a locally resonant supercell structure composed of five types of locally resonant single primitive cells. Firstly, the band structure of the LRPCWMPCCS is calculated using the finite element method, and compared with the band structure of traditional LRPC. Secondly, the frequency response function of the LRPCWMPCCS is calculated to evaluate its attenuation effect on elastic waves in the BG frequency range, and the generation mechanism of its locally resonant BG is explored by analyzing the displacement field and energy distribution characteristics at the BG edge. Then, the equivalent model of the LRPCWMPCCS is established for theoretical calculation of the BG range. Finally, the vibration isolation performance of LRPCWMPCCS wave barrier in practical engineering is analyzed, and the application prospects of the LRPCWMPCCS are discussed. The results show that the LRPCWMPCCS designed in this paper can open the multifrequency BGs, and the BGs width is wider. The number of BGs opened is positively correlated with the type of primitive cells inside the LRPCWMPCCS. Within the BG frequency range, the LRPCWMPCCS has a good attenuation effect on vibration waves, with attenuation values exceeding 20 dB. The spring-mass system equivalent model of the LRPCWMPCCS can accurately calculate its BG range and has good accuracy. The LRPCWMPCCS wave barrier has remarkable control and attenuation effect on vibration. Among them, the maximum vibration acceleration of traditional LRPC wave barrier and LRPCWMPCCS wave barrier is reduced by 18.51% and 39.50%, respectively. The relevant research results of this paper have great value and prospects in the design of LRPC with multifrequency and wide BGs, which can also provide a new method and idea for solving vibration and noise problems. [ABSTRACT FROM AUTHOR]

Landau levels, previously proposed and verified in condensed matter systems, are conventionally achieved by introducing an external magnetic field that interacts with electrons. In phononic systems, people have proposed the method of applying strain to structures to form artificial synthetic magnetic fields, which in turn induces the emergence of Landau levels. While most of the current implementations about Landau levels are based on three-dimensional (3D) Weyl systems, the experimental realization of chiral Landau levels in two-dimensional (2D) Dirac acoustic systems remains an open and interesting topic. In this work, we present an innovative approach to generate the chiral Landau levels within a 2D acoustic system by introducing an in-plane artificial pseudomagnetic field. Through breaking the spatial parity symmetry and opening the Dirac cones, we introduce position-dependent effective mass terms to Hamiltonian and confirm the existence of chiral Landau levels by simulations and experiments. Furthermore, We verify the strong robustness of the zeroth Landau level to different kinds of defects. This work provides a feasible way to realize chiral Landau levels in 2D acoustic systems and suggests potential applications in other 2D artificial structures. [ABSTRACT FROM AUTHOR]

Photonic crystals are periodic dielectric structures that create photonic band gaps depending on the geometry of the lattice elements and the material properties. These structures allow light to be easily controlled, guided, and confined due to the tunability and adjustability of their design parameters. Conventional photonic crystals are typically designed with high-symmetry unit cells, while low-symmetry structures are created by breaking this symmetry. Low-symmetry structures are more sensitive to light manipulation and offer greater control and flexibility over light through geometric diversity. This study investigates the resonance effect in a cavity structure composed of a square lattice photonic crystal made of low-symmetry C2-type dielectric rods. The dependence of the resonance mode on the low-symmetry parameters was investigated and it was shown that, in contrast to other studies, mode splitting or merging can be achieved and tuned by exploiting and perturbing the intrinsic symmetry properties of the low-symmetry photonic crystal structure. The band structure, transmission spectra, and resonance frequencies of the low rotational symmetry photonic crystal were obtained using Lumerical and MEEP software. The analysis of resonance splitting and optical properties by symmetry manipulation will contribute to the understanding of light collimation and trapping. [ABSTRACT FROM AUTHOR]

This study proposes an effective strategy to enlarge the band gaps of holey phononic crystal strips. The approach involves identifying each band and its key influencing factors, then implementing targeted synthetic adjustments like geometry optimization and embedment to reposition the relevant bands, and finally achieving larger band gaps. The main band gap can be enlarged from 47% to 64% with slight modifications. Furthermore, this optimal result is only achieved through the synergistic action of different methods, each of which has small or even counteractive individual effects. The design strategy starts from large-scale to small-scale adjustments, culminating in specific case-by-case adjustments. It presents new possibilities for enhancing phononic crystals. [ABSTRACT FROM AUTHOR]