Crystals

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11 pages, 2399 KiB

Open AccessArticle

Defect-Free Phononic Crystal Waveguides on GaAs

by Edward Muzar and James A. H. Stotz

Crystals 2023, 13(11), 1540; https://doi.org/10.3390/cryst13111540 - 27 Oct 2023

Viewed by 806

A phononic crystal waveguide is presented that consists of the inverse of a typical structure. Instead of a defect waveguide within an extended phononic crystal, this waveguide consists of a phononic crystal of finite width, and the phononic crystal itself is composed of [...] Read more.

A phononic crystal waveguide is presented that consists of the inverse of a typical structure. Instead of a defect waveguide within an extended phononic crystal, this waveguide consists of a phononic crystal of finite width, and the phononic crystal itself is composed of a shallow array of holes. The acoustic velocity is actually reduced in the phononic crystal region, which subsequently enables the waveguiding of the acoustic wave underneath the micro-structured surface. As the width of the waveguide increases with the number of inclusions, the waveguide morphs from an unstructured surface to an extended phononic crystal with a transitional modal region of an intermediate number of inclusions that is suitable for waveguiding. For the chosen phononic crystal parameters in terms of the hole depth and filling fraction, the optimum waveguide width of four inclusions is determined. Full article

(This article belongs to the Special Issue Advances in Phononic Crystals and Elastic Metamaterials)

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21 pages, 7558 KiB

Open AccessArticle

Regulation Mechanism of the Shock Waves in a Pentamode Lattice-Ring Structure Subjected to Collision

by Zhenhua Zhang and Bangyi Han

Crystals 2022, 12(12), 1749; https://doi.org/10.3390/cryst12121749 - 2 Dec 2022

Viewed by 1014

Abstract

This paper hopes to explore the application potential of pentamode materials in the field of shock protection. Hammer percussion tests revealed that the peak strain of the inner-ring front shock surface of the pentamode lattice-ring structure is 103.9% of that of the inner-ring [...] Read more.

This paper hopes to explore the application potential of pentamode materials in the field of shock protection. Hammer percussion tests revealed that the peak strain of the inner-ring front shock surface of the pentamode lattice-ring structure is 103.9% of that of the inner-ring rear shock surface. According to the simulation results, for a solid ring of equal mass made of the same base material, the ratio mentioned above reaches 3385.7%. Compared with the solid ring of equal mass made of the same base material, the pentamode lattice-ring structure saw a decline of 65.5% in the peak strain of its inner-ring front shock surface. The distribution laws of the group velocity characterizing energy-flow characteristics were discovered by calculating cell dispersion curves in various layers of the pentamode lattice-ring structure. The laws governing the effects of cellular structure parameters on group velocity anisotropy and pentamode characteristic parameters were also revealed. It was found that the deflection angle of the energy-flow vector is positively correlated with group velocity anisotropy and that the effects of pentamode characteristic parameters π and μ on the deflection angle of the energy-flow vector vary greatly in different value ranges. The deflection angle of the energy-flow vector has a decisive effect on the protection performance of the pentamode lattice-ring structure. The conclusions of this study can provide some theoretical support for the shock protection of submarine structures. Full article

(This article belongs to the Special Issue Advances in Phononic Crystals and Elastic Metamaterials)

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22 pages, 7408 KiB

Open AccessArticle

Electro-Acoustic Properties of Scandium-Doped Aluminum Nitride (Sc_xAl_1-xN) Material and its Application to Phononic Crystal-Coupled SAW Devices

by Fahima Arab, Fares Kanouni, Rafik Serhane, Yan Pennec, Zafer Özer and Khaled Bouamama

Crystals 2022, 12(10), 1431; https://doi.org/10.3390/cryst12101431 - 10 Oct 2022

Cited by 5 | Viewed by 2358

Abstract

Within the framework of the Density Functional Theory, the elastic, dielectric, and piezoelectric coefficients of w-Sc_xAl_1−xN material were investigated for scandium (Sc) concentrations x = 0 to 0.375. The electro-acoustic properties are used to investigate the frequency [...] Read more.

Within the framework of the Density Functional Theory, the elastic, dielectric, and piezoelectric coefficients of w-Sc_xAl_1−xN material were investigated for scandium (Sc) concentrations x = 0 to 0.375. The electro-acoustic properties are used to investigate the frequency response of the SAW delay line, based on the tilt θ° of the normal c-axis of the w-Sc_xAl_1−xN piezoelectric thin film. We found that the piezoelectric response is improved as the Sc concentration increases, which is consistent with existing works in the literature. A 2D-phononic crystal pillars was then grafted on top of the surface, and the dependence of the acoustic band gaps is investigated with the help of the finite element method as a function of the Sc concentration and the tilted angle of w-Sc_0.375Al_0.625N. It was found that the two first band gaps exhibit a shift toward low frequencies with increasing Sc concentration. Moreover, the second acoustic bandgap is more sensitive to the inclination angle than the first. Furthermore, the insertion loss (S₂₁) of w-Sc_0.375Al_0.625N is improved by 22 dB at θ° = 60°. The c-axis tilted Sc_0.375Al_0.625N-SAW delay line coupled with 2D-phononic crystals is a promising structure for low-loss and high-frequency SAW devices. Full article

(This article belongs to the Special Issue Advances in Phononic Crystals and Elastic Metamaterials)

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15 pages, 3417 KiB

Open AccessArticle

Comparison of Brillouin Light Scattering and Density of States in a Supported Layer: Analytical and Experimental Study

by Ossama El Abouti, John Cuffe, El Houssaine El Boudouti, Clivia M. Sotomayor Torres, Emigdio Chavez-Angel, Bahram Djafari-Rouhani and Francesc Alzina

Crystals 2022, 12(9), 1212; https://doi.org/10.3390/cryst12091212 - 28 Aug 2022

Cited by 2 | Viewed by 1483

Abstract

We provide a detailed analytical calculation of the Brillouin light scattering (BLS) intensity of a layer on a substrate, taking into account both photoelastic and moving boundary (ripple effect) mechanisms, and give a comparison between BLS intensity and density of states (DOS) to [...] Read more.

We provide a detailed analytical calculation of the Brillouin light scattering (BLS) intensity of a layer on a substrate, taking into account both photoelastic and moving boundary (ripple effect) mechanisms, and give a comparison between BLS intensity and density of states (DOS) to determine the dispersion curves of longitudinal guided modes in the supported layer. In particular, in the case where the mismatch between the elastic parameters of the substrate and the adsorbed layer is high, such as in a PMMA layer on a Si substrate, we derive closed-form expressions of BLS and DOS and demonstrate a simple relationship between these two quantities. A very good agreement between experimental and theoretical BLS spectra was found and compared to theoretical DOS spectra. In particular, we show that while the peaks in the DOS present a uniform behavior, the BLS spectra follows a sine cardinal (sinc) function shape around a given frequency fixed by the chosen laser wavelength. The theoretical calculation is performed within the framework of the Green’s function approach. Full article

(This article belongs to the Special Issue Advances in Phononic Crystals and Elastic Metamaterials)

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16 pages, 10577 KiB

Open AccessArticle

Study on the Bandgap Characteristics and Vibration-Reduction Mechanism of Symmetric Power-Exponent Prismatic Phononic Crystal Plates

by Xing Jin and Zhenhua Zhang

Crystals 2022, 12(8), 1125; https://doi.org/10.3390/cryst12081125 - 11 Aug 2022

Cited by 2 | Viewed by 1480

Abstract

In this paper, a symmetric power-exponent prismatic phononic crystal configuration was proposed for the vibration reduction of thin plate structures, and the mechanism of bandgap generation and the influencing factors of the band gaps were analyzed. The results showed that the proposed symmetric [...] Read more.

In this paper, a symmetric power-exponent prismatic phononic crystal configuration was proposed for the vibration reduction of thin plate structures, and the mechanism of bandgap generation and the influencing factors of the band gaps were analyzed. The results showed that the proposed symmetric power-exponent prismatic phononic crystal structure has three complete band gaps of bending waves, where the width of the second band gap can go up to 1639 Hz. The band gaps of bending waves of the phononic crystal were verified using a combination of numerical simulations and experimental methods, and subsequently, the bandgap characteristics and energy-focusing effect of the phononic crystals were effectively used to suppress the bending vibration of the thin plate. With the increase in prismoid height of the structure, the width of the first band gap expanded, while the bandwidths of the other two band gaps narrowed down. It was observed that an increase in the power of the power-exponent prismoid would reduce the starting and ending frequencies of the band gaps, whereas an increase in the prismoid edge thickness would weaken the energy-focusing effect and narrow the band gaps gradually. Our research results provide a new technique and a pathway to realize vibration reduction in thin plate structures. Full article

(This article belongs to the Special Issue Advances in Phononic Crystals and Elastic Metamaterials)

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12 pages, 4216 KiB

Open AccessArticle

Photo-Elastic Enhanced Optomechanic One Dimensional Phoxonic Fishbone Nanobeam

by Fu-Li Hsiao, Ying-Pin Tsai, Wei-Shan Chang, Chien-Chang Chiu, Bor-Shyh Lin and Chi-Tsung Chiang

Crystals 2022, 12(7), 890; https://doi.org/10.3390/cryst12070890 - 23 Jun 2022

Cited by 2 | Viewed by 1443

Abstract

We investigated the strength of acousto-optical (AO) interaction in one-dimensional fishbone silicon nanobeam computationally. The structure can generate phononic and photonic band gaps simultaneously. We use defect cavity optical mode and slow light mode to interact with acoustic defect modes. The AO coupling [...] Read more.

We investigated the strength of acousto-optical (AO) interaction in one-dimensional fishbone silicon nanobeam computationally. The structure can generate phononic and photonic band gaps simultaneously. We use defect cavity optical mode and slow light mode to interact with acoustic defect modes. The AO coupling rates are obtained by adding the optical frequency shifts, which result from photo-elastic effect and moving-boundary effect disturbances. The AO coupling rates are strongly dependent on the overlap of acoustic and optical mode distribution. The strength of AO interaction can be enhanced by choosing certain acoustic defect modes that are formed by the stretching of wings and that overlap significantly with optical fields. Full article

(This article belongs to the Special Issue Advances in Phononic Crystals and Elastic Metamaterials)

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17 pages, 1907 KiB

Open AccessArticle

A Biosensor Based on Bound States in the Continuum and Fano Resonances in a Solid–Liquid–Solid Triple Layer

by Ilyasse Quotane, Madiha Amrani, Cecile Ghouila-Houri, El Houssaine El Boudouti, Leonid Krutyansky, Bogdan Piwakowski, Philippe Pernod, Abdelkrim Talbi and Bahram Djafari-Rouhani

Crystals 2022, 12(5), 707; https://doi.org/10.3390/cryst12050707 - 16 May 2022

Cited by 5 | Viewed by 1798

Abstract

We propose a simple solid–liquid–solid triple layer biosensor platform based on bound states in the continuum (BICs) and Fano resonances to detect the acoustic properties of liquids and apply the method to a mixture of water and albumin with various concentrations. The solid–liquid–solid [...] Read more.

We propose a simple solid–liquid–solid triple layer biosensor platform based on bound states in the continuum (BICs) and Fano resonances to detect the acoustic properties of liquids and apply the method to a mixture of water and albumin with various concentrations. The solid–liquid–solid triple layer is composed of an epoxy as a solid layer and an albumin–water mixture as a liquid layer, and the entire system is immersed in water. In this work, we show that the structure exhibits a high sensitivity (S), quality factor (Q), and figure of merit (FOM) with a better detection limit (DL) in the vicinity of the BICs where the transmission spectra exhibit Fano resonances. The Fano resonances shift towards high frequencies as the concentration increases. The detection limit can reach very small values for a small albumin concentration (

4.7 %

). In addition, for a given concentration and layer thickness of the sensing material, we show the effect of the incidence angle on the efficiency of the sensor in terms of the sensitivity and quality factor. The proposed structure can be designed from low-cost material and can be used as a sensor to detect different types of liquids and gases as well. Full article

(This article belongs to the Special Issue Advances in Phononic Crystals and Elastic Metamaterials)

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11 pages, 5213 KiB

Open AccessArticle

Influence Mechanism of a New-Style Resonator on Band Gap of Locally Resonant Phononic Crystal Double Panel Structure

by Yujia Xiang, Molin Chen, Denghui Qian and Zhiyu Shi

Crystals 2022, 12(5), 609; https://doi.org/10.3390/cryst12050609 - 26 Apr 2022

Cited by 2 | Viewed by 1522

Abstract

Based on the previous studies on the stubbed-on locally resonant phononic crystal (LRPC) double panel structure (DPS) made of a two-dimensional periodic array of a two-component cylindrical LR pillar connected between the upper and lower plates, the stubbed-on LRPC DPS with soft shell [...] Read more.

Based on the previous studies on the stubbed-on locally resonant phononic crystal (LRPC) double panel structure (DPS) made of a two-dimensional periodic array of a two-component cylindrical LR pillar connected between the upper and lower plates, the stubbed-on LRPC DPS with soft shell surrounded and simplified model with additional springs surrounded are proposed. According to the changes in structural form, the wider band gap is opened, and the novel formation mechanism of the band gap is revealed. Finite element method (FEM) is applied to calculate the band structures. Numerical results and further analysis demonstrate that the soft shell only affects the bands corresponding to symmetric vibration mode and makes the bands shift up. In addition, the influences of density and Poisson’s ratio of soft shell on the band gap can be ignored, but the starting frequency keeps still, and band gap width increases first and then keeps constant with the increase of elasticity modulus. All the results provide a theoretical basis for the study of vibration and noise resistance in engineering. Full article

(This article belongs to the Special Issue Advances in Phononic Crystals and Elastic Metamaterials)

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11 pages, 5950 KiB

Open AccessArticle

Elastic Metamaterials of Hexagonal Unit Cells with Double-Cone Arms from Pentamode to Band Gap at Low Frequencies

by Qi Li and Mingquan Zhang

Crystals 2022, 12(5), 604; https://doi.org/10.3390/cryst12050604 - 25 Apr 2022

Cited by 4 | Viewed by 1517

Abstract

Metamaterials are artificial materials with properties that can be designed by man-made structures. Pentamode metamaterials only support compressional stresses at specific frequency ranges, and a band gap is a frequency range where no stresses are supported. In this paper, an elastic metamaterial with [...] Read more.

Metamaterials are artificial materials with properties that can be designed by man-made structures. Pentamode metamaterials only support compressional stresses at specific frequency ranges, and a band gap is a frequency range where no stresses are supported. In this paper, an elastic metamaterial with hexagonal unit cells is studied where pentamode bands or band gaps at low frequencies are obtained by varying the inner structures. The effects of structural and geometric parameters on the band width of pentamode bands or band gaps are analyzed. Simulations of materials composed of primitive cells with pentamode or band gap properties are conducted with harmonic stimulation based on the finite element method. The metamaterials can be applied as pentamode metamaterials or vibration isolation materials. Full article

(This article belongs to the Special Issue Advances in Phononic Crystals and Elastic Metamaterials)

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