Transparent, Flexible, and Highly Sensitive Piezocomposite Capable of Harvesting and Monitoring Kinetic Movements of Microbubbles in Liquid

In this study, a zinc oxide (ZnO)-decorated nickel microfiber (ZNMF)-based piezoelectric nanogenerator (ZNMF-PENG) using electrospinning, metal electroplating, electrospraying, and ceramic growing techniques is fabricated. The combination of these techniques enables the ZNMF-PENG to possess high transparency and flexibility that are difficult to achieve through the existing piezoceramic-based PENGs. In particular, the presence of innumerable piezoceramic ZnO nanowires inside the ZNMF-PENG allows for detecting microbubble movements having an extremely low buoyancy force of 0.009 N, which is beneficial for detecting cavitation. Moreover, in comparison to previously reported PENGs fabricated using an electrospinning technique, the ZNMF-PENG demonstrates the highest energy-harvesting efficiency of 8750 V N⁻¹ m⁻². The novel approach in materials and methods proposed in this study is expected to contribute to the further advancement in developing transparent, flexible, and performance-improved PENGs applicable to various industrial applications.