We explore the harvesting of acoustic waves by leveraging 3D-printed gradient-index phononic crystal (GRIN-PC) lens designs. The concept is demonstrated numerically and experimentally for acoustic waves in air and under water by using piezoelectric transduction as the energy harvesting scheme. Unit cell design procedure to achieve the required refractive index profile and numerical simulations of the band structure are executed using a high-fidelity finite-element model, followed by 3D simulations of the acoustic wave field for validation of the lens performance. Performance enhancement by focusing acoustic waves is quantified along with the level of anisotropy in the resulting 3D lens design. Additionally, a fully coupled multiphyics framework is used to cover both acoustic-structure interaction, piezoelectric coupling, as well as electrical load impedance. Finite-element simulations include the GRIN-PC lens and the harvester components along with basic electrical load to quantify the electrical power. In the full numerical simulations, design parameters such as the unit cell design, aperture of the lens, directional effects and anisotropy are explored in detail. Specifically, efforts are summarized on the unit cell design to minimize the directional sensitivity, toward making the lens close to omnidirectional. Experiments are performed to quantify the harvested power and to validate various numerical results.


Enhanced Sound Energy Harvesting by Leveraging Gradient-Index Phononic Crystals

Division / Sponsors: 
Aerospace Division

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2020/volume/84027

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