Multi-frequency sound energy harvesting using Helmholtz resonators with irradiated cross-linked polypropylene ferroelectret films

Harvesting multi-frequency sound energy from environmental noise is a meaningful topic to supply for potential devices. In this work, we constructed an array of Helmholtz resonators (HRs) with cross-linked polypropylene (IXPP) ferroelectret films on the inner walls HR cavities, whose resonant frequencies range 300 800 Hz and quasi-static piezoelectric coefficient d33 230 pC/N. The harvesting performance IXPP investigated, both theoretically experimentally, in single various sizes, showing high conversion capability close HRs, e.g., 337, 375, 445, 522, 588, 661, 739, 782, 795 Hz, experiment. By putting one, two, three, four samples nine different sized HRs series connection order, measured average output power 3.16, 5.31, 7.36, 8.66 nW at frequencies. It shows that has been significantly improved multiple by films. parallel, optimal electrical resistance increases quasilinear way compared number HRs. These results are helpful designing efficient harvesters broadband frequency range.