Redesigning finite metasurfaces for enhanced energy harvesting with lead-free (K, Na)NbO3 ceramics

Metasurfaces provide a transformative platform for enhancing energy harvesting by enabling efficient energy localization and amplification in a compact structure. Despite this potential, current research largely focuses on numerical and analytical methods, with limited experimental studies comparing the outputs of piezoelectric energy harvesters integrated with metasurfaces. This often leads to design discrepancies that undermine energy amplification efficacy. This study proposes an optimal metasurface redesign to maximize energy amplification with lead-free (K, Na)NbO₃ (KNN) ceramic-based piezoelectric energy harvesters. Our novel metasurface design is effective in real-world vibration environments, such as railways and water pumps. Results show that integrating eco-friendly KNN energy harvesters into enhanced flexural vibration fins necessitates this redesign, achieving over 20.6 times greater power output than the original design. Additionally, the choice between soft and hard lead-free KNN ceramics significantly influences electromechanical coupling and experimental amplitude, with soft ceramics offering considerable advantages for energy harvesting. This research highlights the importance of a tailored metasurface redesign, enhancing the efficiency of energy harvesting systems and supporting practical applications in sustainable energy technologies.