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

We explore a phononic crystal Luneburg lens through design, fabrication, and analysis for omnidirectional elastic wave focusing and enhanced energy harvesting both numerically and experimentally. The proposed lens is formed using hexagonal unit cells with blind holes of different diameters, which ar...

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Bibliographic Details
Published in:Applied physics letters 2017-07, Vol.111 (1)
Main Authors: Tol, S., Degertekin, F. L., Erturk, A.
Format: Article
Language:English
Subjects:
Applied physics
Computer simulation
Crystals
Elastic waves
Energy harvesting
Finite element method
Harvesters
Incidence angle
Incident waves
Lamb waves
Lenses
Piezoelectricity
Plane waves
Refractivity
Wave excitation
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Summary:We explore a phononic crystal Luneburg lens through design, fabrication, and analysis for omnidirectional elastic wave focusing and enhanced energy harvesting both numerically and experimentally. The proposed lens is formed using hexagonal unit cells with blind holes of different diameters, which are determined according to the Luneburg lens refractive index distribution obtained by finite-element simulations of the lowest asymmetric mode Lamb wave band structure. Wave simulations are performed numerically under plane wave excitation from a line source, and focusing is observed at the opposite border of the lens with respect to the incident wave direction. Numerically simulated elastic wave focusing results are validated through a set of experiments. Omnidirectionality is demonstrated by testing the lens under plane wave excitation for different angles of incidence. With piezoelectric energy harvesters located at the boundary of the phononic crystal Luneburg lens, more than an order of magnitude larger power output can be extracted as compared to the baseline case of energy harvesting without the lens under the same plane wave excitation.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4991684