Long-term performance of innovative hexa-fold piezoelectric energy harvester for self-powered leadless pacemakers

In the pursuit of solving the energy storage issues of leadless pacemakers, this study presents a piezoelectric energy harvester (PEH) for self-powering. The mismatch in natural frequencies between the cardiac cycles and the piezoelectric structure affects energy generation. In this research, a groundbreaking hexa-fold PEH (HF-PEH) with contact impacts was proposed to generate high energy density from cardiac cycles. The HF-PEH was manufactured and tested in vivo inside a living pig’s heart. Subsequently, we subjected this HF-PEH prototype to laboratory cardiac acceleration for over 35 million cardiac cycles to investigate its long-term performance. Post-test material analysis using SEM and x-ray energy-dispersive spectroscopy was conducted to investigate the material structure. The HF-PEH generated maximum voltage, current, and power of 1.4 V, 458.5 µA, and 367.2 µW at in-vivo animal trial with 71 beats per minute, which are the same or higher than the values a leadless pacemaker paces into the body. Post-test material analyses showed that the piezoelectric ceramic remained intact while the electrode condition changed. A verified finite element model was used to study the long-term electrode layer erosion condition with respect to the electric displacement field. Since the electrode erosion is limited to the contact-based impact region, limited power degradation in long-term performance was observed. This study also highlights the roles of electrode materials and presents potential protective methods and materials to mitigate electrode performance degradation. Our findings pave the way for practical energy harvesting applications for leadless pacemakers and underscore the need for advanced piezoelectric coatings in contact-based energy harvesting systems.