Void-incorporated substrates for high-performance piezoelectric vibration energy harvesting

This paper presents a geometry-based design strategy to enhance strain distribution and improve the power generation of cantilever piezoelectric vibration energy harvesters. A finite element (FE) model of a cantilever harvester is first developed in COMSOL Multiphysics and validated against experimental and numerical results from the literature to ensure accurate prediction of dynamic response, output voltage, and harvested power. Following validation, the FE model is used to investigate a series of novel void-incorporated substrate designs, including square, cylindrical, and analytically defined sinusoidal void patterns. These designs are developed under consistent geometric and material constraints to enable a fair comparison. The introduction of periodic voids modifies the effective bending stiffness of the beam, increasing structural compliance, enhancing strain distribution in the piezoelectric layer, and shifting the resonance frequency toward lower values. Comprehensive analyses, including eigenfrequency, frequency-domain, and load resistance optimization studies, reveal that the proposed geometric modifications significantly improve energy harvesting performance. Among the studied configurations, the sinusoidal and cylindrical patterns demonstrate the most effective performance, with sinusoidal pattern #01 achieving the highest maximum power output, corresponding to an improvement of approximately 45.7% compared to the conventional solid substrate. Overall, the results demonstrate that tailoring substrate geometry through strategically designed void patterns is an effective and practical approach for enhancing the performance of piezoelectric energy harvesters, offering a promising pathway toward efficient and cost-effective self-powered systems.