Abstract
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 A0 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.
Highlights
Metamaterials, in their modern guise, emerged about two decades ago in optics [1] and their potential in creating artificial media, with properties not found in nature, and the consequent opportunities in wave physics, have triggered intense research activity
We concentrate upon elastic plate models for which the A0 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
Resonant metamaterials are characterised by resonating elements, analogous to Helmholtz resonators [18] in acoustics and Fano resonances [19], enabling the creation of low-frequency band-gaps in structures relatively small compared to the wavelength; these ideas can be augmented by tuning or spatially grading the resonators to broaden or decrease band-gaps
Summary
Jacopo M De Ponti1,2 , Andrea Colombi , Raffaele Ardito , Francesco Braghin , Alberto Corigliano and Richard V Craster.
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