Curvature-Specific Coupling Electrode Design for a Stretchable Three-Dimensional Inorganic Piezoelectric Nanogenerator.

Structures such as 3D buckling have been widely used to impart stretchability to devices. However, these structures have limitations when applied to piezoelectric devices due to the uneven distribution of internal strain during deformation. When strains with opposite directions simultaneously affect piezoelectric materials, the electric output can decrease due to cancellation. Here, we report an electrode design tailored to the direction of strain and a circuit configuration that prevents electric output cancellation. These designs not only provide stretchability to piezoelectric nanogenerators (PENGs) but also effectively minimize electric output loss, achieving stretchable PENGs with minimal energy loss. These improvements were demonstrated using an inorganic piezoelectric material (PZT thin film) with a high piezoelectric coefficient, achieving a substantial maximum output power of 8.34 mW/cm. Theoretical modeling of the coupling between mechanical and electrical properties demonstrates the dynamics of energy harvesting, emphasizing the electrode design. In vitro and in vivo experiments validate the device's effectiveness in biomechanical energy harvesting. These results represent a significant advancement in stretchable PENGs, offering robust and efficient solutions for wearable electronics and biomedical devices.