Phononic crystal Luneburg lens for omnidirectional elastic wave focusing and energy harvesting

Tol, Şerife; Degertekin, F. Levent; Ertürk, Alper

doi:10.1063/1.4991684

Cited by 156 publications

(86 citation statements)

References 35 publications

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“…Piezoelectric energy harvesting is driven by the deformation of the host structure due to mechanical or acoustic vibrations that convert to an electrical potential via embedded piezoelectric materials. To increase harvester efficiency, using ideas based around structuring surfaces, several approaches such as creating a parabolic acoustic mirror, point defects in periodic phononic crystals and acoustic funnels have been employed [28][29][30][31]; lenses to concentrate narrow band vibrations have been proposed using phononic crystals [32][33][34], ideas based around localised defect states [35], and resonant metamaterials endowed with piezoelectric inserts have appeared very recently [36]. Our aim here is to complement these studies by using a graded array to create a metawedge [37], and introduce piezoelectric elements into the array, this addresses one of the main challenges in energy harvesting which is to achieve broadband energy production from ambient vibration spectra.…”

Section: Introductionmentioning

confidence: 99%

Graded elastic metasurface for enhanced energy harvesting

Colombi²,

et al. 2020

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In elastic wave systems, combining the powerful concepts of resonance and spatial grading within structured surface arrays enable resonant metasurfaces to exhibit broadband wave trapping, mode conversion from surface (Rayleigh) waves to bulk (shear) waves, and spatial frequency selection. Devices built around these concepts allow for precise control of surface waves, often with structures that are subwavelength, and utilise Rainbow trapping that separates the signal spatially by frequency. Rainbow trapping yields large amplifications of displacement at the resonator positions where each frequency component accumulates. We investigate whether this amplification, and the associated control, can be used to create energy harvesting devices; the potential advantages and disadvantages of using graded resonant devices as energy harvesters is considered. We concentrate upon elastic plate models for which the A 0 mode dominates, and take advantage of the large displacement amplitudes in graded resonant arrays of rods, to design innovative metasurfaces that trap waves for enhanced piezoelectric energy harvesting. Numerical simulation allows us to identify the advantages of such graded metasurface devices and quantify its efficiency, we also develop accurate models of the phenomena and extend our analysis to that of an elastic half-space and Rayleigh surface waves.

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Section: Introductionmentioning

confidence: 99%

Graded elastic metasurface for enhanced energy harvesting

Colombi²,

et al. 2020

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“…The acoustic mode inside the bandgap exhibits high mechanical quality factor making the optomechanical phonon coherent manipulation possible. Fig.7(d) illustrates the confinement of elastic waves in the GRIN devices can be used for energy harvesting [66,67].…”

Section: Grin Devices For Flexural Wavesmentioning

confidence: 99%

“…GRIN devices can also be designed with negative index of refraction at frequencies laying in the first negative slope of the acoustic band structure [21]. However, these devices would be narrow band and it may limit potential applications.GRIN phononic crystals and metamaterials can be applied to various types of waves in a long frequency limit, such as surface water waves [35,36] for a few Hz, air-borne sound waves [19,[37][38][39][40][41][42][43][44][45][46] for 10 3 Hz-10 5 Hz, water-borne acoustic waves [20,27,[47][48][49] for 10 4 Hz-10 6 Hz, Rayleigh waves[50-54] for 10Hz-10 8 Hz, Lamb waves [23-25, 28, 55-67] for 10 3 -10 8 Hz, among others, with functionalities like focusing [18,19], waveguiding [65,68], mirage[69], beam splitting or deflection [36,57,58], cloaking [50,59] or energy harvesting [66,67,70]. It is in the domain of…”

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confidence: 99%

“…(a) Acoustic waveguide by combining GRIN flat lens and phononic crystals in a 80 µm thick plate. SEM image shows samples in the rectangular dotted box with the radii of gradient holes vary from 15µm to 25µm[93];(b) acoustic metalens by combining GRIN flat lens and pillars (30 µm radius) to exhibit the near-field subdiffraction focusing[63]; (c) 1D phoxonic crystal with varied unit cells (the minimum radius of holes is 100 nm) to exhibit the optomechanical interactions[73]; (d) GRIN flat rectangular lens and Luneburg circular lens for energy harvesting[66,67].In Sec.3, Eq. (10) gives a useful tool to calculate the effective parameters of phononic crystal plates whose thickness is fixed as a constant.…”

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confidence: 99%

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Gradient index phononic crystals and metamaterials

2019

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Phononic crystals and acoustic metamaterials are periodic structures whose effective properties can be tailored at will to achieve extreme control on wave propagation. Their refractive index is obtained from the homogenization of the infinite periodic system, but it is possible to locally change the properties of a finite crystal in such a way that it results in an effective gradient of the refractive index (GRIN). In such case the propagation of waves can be accurately described by means of ray theory, and different refractive devices can be designed in the framework of wave propagation in inhomogeneous media. In this paper we review the different devices that have been studied for the control of both bulk or guided acoustic waves based on graded phononic crystals.In this regime the wavelength l of the acoustic field is comparable to the periodicity a of the lattice, l»a, and to be observable it is also required that the thickness D of the bulk phononic crystals be at least four or five periodicities, D>>a. In the subwavelength range, l>>a , it is possible to find local resonances in the scatterers and the designed structures exhibit hybridization band gaps which give rise to novel effects such as negative mass density or negative elastic modulus. In this exotic regime the structure behaves as a special type of materials called "acoustic metamaterials", which were firstly proposed in the seminal work [3] in 2000. Over the past two decades, dramatically increasing efforts have been devoted to the study of acoustic artificial structured materials driven by both fundamental scientific curiosities with properties not found previously and diverse potential applications with novel functionalities [4][5][6][7][8][9][10][11][12][13][14][15][16].While interesting, most of the extraordinary properties of metamaterials are in general singlefrequency or narrow-band, since outside the resonant regime metamaterials behave as common composites. However, non-resonant phononic crystals in the low frequency regime behave as homogeneous non-dispersive materials whose effective parameters can be easily tailored, and in this regime gradient index (GRIN) acoustic materials, or GRIN devices, are easily doable. These devices were firstly proposed for acoustic waves by Torrent et al in 2007[17] and for elastic waves by Lin et al in 2009[18], and they allow to manipulate acoustic waves to enforce them to follow curved trajectories. They are characterized by a spatial variation of acoustic refractive index, which is designed by locally changing the geometry of units. For instance, the effective index obviously depends on the filling ratio of scatterers, namely the size of scatterers, which is initially proposed for gradient index control of acoustic waves [17][18][19]; instead, the variation in the lattice spacing while keeping the size of scatterers is also achievable [20,21]; for triangular shape of scatterers, rotating the angles of the triangular shape can also affect the effective acoustic velocity [22]; for lead-rubber pillared met...

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“…In the past decade, the emerging area of metasurface research has made it possible to manipulate optical and electromagnetic waves in an almost arbitrary way by tuning the phase gradient at the sub-wavelength scale. [1][2][3][4][5] This concept has also found applications in acoustic designs such as focal lenses, [6][7][8] anomalous reflection and refraction, [9][10][11][12][13][14] , and generation of acoustic orbital angular momentum. 15,16 Elastic metasurfaces 17,18 are relatively unexplored; they present specific challenges due to the mode conversion at the material interface which makes the phase modulation more complicated.…”

Section: Introductionmentioning

confidence: 99%

Elastic metasurfaces for splitting SV- and P-waves in elastic solids

Norris

2017

Journal of Applied Physics

109

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Although recent advances have made it possible to manipulate electromagnetic and acoustic wavefronts with sub-wavelength metasurface slabs, the design of elastodynamic counterparts remains challenging. We introduce a novel but simple design approach to control SV-waves in elastic solids. The proposed metasurface can be fabricated by cutting an array of aligned parallel cracks in a solid such that the materials between the cracks act as plate-like waveguides in the background medium. The plate array is capable of modulating the phase change of SV-wave while keeping the phase of P-wave unchanged. An analytical model for SV-wave incidence is established to calculate the transmission coefficient and the transmitted phase through the platelike waveguide explicitly. A complete 2π range of phase delay is achieved by selecting different thicknesses for the plates. An elastic metasurface for splitting SV-and P-waves is designed and demonstrated using full wave finite element (FEM) simulations. Two metasurfaces for focusing plane and cylindrical SV-waves are also presented.

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Phononic crystal Luneburg lens for omnidirectional elastic wave focusing and energy harvesting

Cited by 156 publications

References 35 publications

Graded elastic metasurface for enhanced energy harvesting

Graded elastic metasurface for enhanced energy harvesting

Gradient index phononic crystals and metamaterials

Elastic metasurfaces for splitting SV- and P-waves in elastic solids

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