Double Defects-induced, Locally-resonant Metamaterial for Broadband Piezoelectric Energy Harvesting

초록

Locally-resonant metamaterials (LRMs), which are artificially-engineered structures consisting of periodically-arranged resonators, have garnered interest for their ability to manipulate wave propagation. If a defect is intentionally induced in LRMs, wave energy can be localized within the defect, a feature that can be leveraged to enhance piezoelectric energy harvesting (PEH) by amplifying the output voltage to incident waves. However, a major limitation of conventional LRMs lies in the narrow bandwidth of the defect mode, which leads to a sharp drop in the output voltage even with slight deviations from the defect band frequency. To address this issue, the present study proposes the use of induced double defects to achieve defect band splitting, thereby enabling broadband PEH. An electromechanically coupled analytical model is developed for LRMs with double defects to investigate the underlying mechanism of defect band splitting. The proposed model facilitates the prediction of defect band splitting via the transfer matrix method and enables the estimation of the output voltage and output electric power across an external electrical resistance using the S-parameter method. As a result, the proposed model predicts a band gap ranging from 867 to 1624 Hz. Introducing a single defect gives rise to a defect band at 1,024 Hz, whereas introducing double defects splits this band into two defect bands at 994 Hz and 1,043 Hz, corresponding to a band splitting of 49 Hz. Under the optimal load resistance of 181,273 ohm, the PEH device attached to the first of the double defects produced 0.009 mW. These results confirm the potential of double defects-induced band splitting for broadband PEH. Notably, this study provides the first analytical approach that captures the electromechanical interactions in LRMs with double defects through explicit physical parameterization, enabling effective prediction and design for broadband PEH.

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