YU-HSI HUANGZhi Chao OngSheng-Lun ChouPei Yi Siow2025-03-212025-03-212025-03-31https://www.scopus.com/record/display.uri?eid=2-s2.0-85215255115&origin=resultslisthttps://scholars.lib.ntu.edu.tw/handle/123456789/725971Recent years have shown increased interest in improving the efficiency of piezoelectric vibration-based energy harvesters (PVEH). The most common boundary condition of a PVEH is the clamped-end or cantilever with rigid supports, making it to perform efficiently at the resonant frequencies of the first two bending modes that are usually at a higher frequency range. The generated output voltage and power is also limited to the deformation from the bending modes of the cantilever PVEH. Thus, to lower the resonant frequencies for practicality in real ambient vibrations and to further increase the generated energy output, this paper proposed a spring boundary condition cantilever PVEH, where the rigid support of a cantilever PVEH was replaced with springs. A clamped-end cantilever PVEH was used as the benchmark for comparison. The springs were computationally modelled as a combination of a tension and a torsional spring to investigate the effect of tension and torsional spring stiffness in reducing the resonant frequencies of the cantilever PVEH using computational methods. To validate the proposed boundary conditions in reducing the resonant frequencies and increasing the generated voltage and power output of a cantilever PVEH, the vibration characteristics of the spring-based cantilever PVEH were extracted numerically and experimentally using amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI), laser Doppler vibrometer (LDV), and impedance analysis, and were compared with the clamped-end cantilever PVEH. Results showed that the spring boundary condition can effectively reduce the resonant frequencies and increase the maximum voltage and power output of the cantilever PVEH due to the increased displacement from the spring supports in the bending modes. The first three resonant frequencies of the cantilever PVEH were reduced from 73 Hz, 284 Hz, and 452 Hz to 15 Hz, 127 Hz, and 439 Hz. The maximum voltage output was increased from 3.1 V to 9.3 V, and the maximum power was increased from 0.093 mW to 8.316 mW, thus making it more practical to be used at a lower or ambient frequency range.boundary conditionmode shapepiezoelectric energy harvesterresonant frequency reductionspringsjournal article10.1088/2631-8695/ada726