Fatigue study and durability improvement of piezoelectric single crystal macro-fiber composite energy harvester

In the energy harvester, the fatigue caused by cyclic vibration is an important challenge affecting the lifetime of the device. The aim of this study is to evaluate the fatigue behavior of the cantilever-type piezoelectric energy harvester (PEH) based on a single crystal macro-fiber composite (SFC), and propose a method for improving durability. The initial output of the fabricated PEH shows 6 mW root mean square power at 0.5 gravitational acceleration at resonance frequency (23 Hz). In fatigue test under cyclic vibration, the dramatic power decrease and waveform distortion caused by the mechanical crack at the top electrode line were identified after 5 × 10⁶ cycles. To improve the issue, the stress distribution on the top electrode line was analyzed by finite element analysis and the reinforced structure was proposed by attaching a 50 µm-thick polyimide film. The reinforced PEH shows the durable output power until 10⁷ fatigue cycles without a significant output power loss. These study potentially can be applied to the development of reliable SFC-based PEH with long-term lifetime.