Fabrication and Comparison of Guided Two-Beam and Four-Beam Piezoelectric Energy Harvester For Low-Frequency Operation

This paper deals with design, fabrication, characterization, and testing of Piezoelectric Vibration Energy Harvester (P-VEH) based on guided two-beam and four-beam-structures proposed for the applications in the low-frequency domain. Each cantilever beam has been deposited with a $2.5~\mu \text{m}$ thick c-axis oriented ZnO film with a passivation layer of $0.5~\mu \text{m}$ thick PECVD SiO₂ on both the sides to avoid the environmental deterioration of ZnO. Al electrodes (top one, as a split electrode) on both sides of the ZnO/SiO₂ structure have been incorporated to capture the electric potentials generated. The displacement and stress for both the designs have been analyzed and reported. A heavy pyramidal shaped seismic mass has been carved out of single crystal Si substrate at the free ends of the cantilevers, thereby providing a higher electric potential. The beam thickness is well controlled by an optimized beam thinning process done through deep reactive ion etching (DRIE). The resonance frequencies using Laser Doppler Vibrometer (LDV), have been measured at 466 Hz and 515 Hz for two-beam and four-beam devices, respectively. In the low-frequency domain (10–1000 Hz), sensitivity analysis has been done experimentally. The two-beam and four-beam devices exhibit net sensitivities of 2.2784 mV/m/s² and 4.09272 mV/m/s², respectively. [2019-0022]