Hybrid piezoelectric–electromagnetic vibration energy harvester using quadruple serpentine structure

Vibration energy harvesting has gained significant attention with the growth of micro- and nanoelectronic devices that operate at ultra-low power levels. This paper presents a hybrid vibration energy harvester (HVEH) based on a compact quadruple serpentine cantilever, integrating piezoelectric and electromagnetic transduction mechanisms. The harvester consists of four piezoelectric strips bonded to the serpentine beams and an electromagnetic module comprising a wound copper coil and a centrally mounted permanent magnet acting as the proof mass. Experimental results demonstrate stable operation in the low-frequency range of 10.5–15 Hz. Under a sinusoidal excitation of 0.1 mm amplitude, the four piezoelectric elements collectively generated an open-circuit voltage of 162 V and a maximum RMS voltage of 106 V, producing a peak output power of 4.74 mW at an optimum load resistance of 620 kΩ. The electromagnetic subsystem generated an open-circuit voltage of 2.129 V and a maximum RMS voltage of 1.152 V, delivering a peak power of 3.79 mW across an optimum load resistance of 350 Ω. The combined hybrid output reached 8.53 mW, demonstrating the effectiveness of the proposed quadruple serpentine structure for low-frequency energy harvesting in self-powered wireless sensor and structural health-monitoring applications.