Synergistic co-design of a piezoelectric energy harvester with multi-stage force amplification and designable structural nonlinearity

Low-frequency vibrational energy harvesting using piezoelectric stacks is fundamentally challenged by an inherent trade-off: high longitudinal stiffness hinders low-frequency resonance, while linear resonant structures offer narrow operational bandwidth. To break this trade-off, this paper presents a novel piezoelectric vibration energy harvester (NPVEH) conceived through a synergistic co-design strategy that effectively couples a multi-stage force amplification mechanism with a structurally nonlinear resonator. The resonator uniquely integrates positive stiffness beams, Euler-buckling negative stiffness beams, and a dual-spring quasi-zero-stiffness mechanism, enabling a continuous stiffness evolution—spanning linear, softening, and hardening regimes—whose profile is parametrically programmed through the geometric dimensions of the constituent stiffness elements. This yields a large-scale frequency bandwidth extension at low frequencies. Concurrently, a three-stage force amplifier, combining triangular and lever mechanisms, delivers a theoretical amplification factor of 16.2, substantially enhancing the electromechanical conversion efficiency of the PZT stack. A comprehensive validation is conducted through theoretical modeling, finite element simulation, and experimental testing. Results demonstrate that under 0.3 g excitation, the device resonates at 10.4 Hz, attaining a peak output power of 10.13 mW with a broadened half-power bandwidth of 2.4 Hz. Furthermore, it charges a 10 μF capacitor to 4.1 V within 20 s and powers 23 LEDs, confirming its practical utility. This work establishes a co-design paradigm that reconciles the conflicting demands of low-frequency activation and wideband operation, offering a robust and efficient solution for powering micro-electronics in vibration-rich environments.