Three-Dimensional Piezoelectric–Triboelectric Hybrid Nanogenerators for Mechanical Energy Harvesting

This study presents experimental results on the production, characterization, and applications of three-dimensionally designed piezoelectric–triboelectric hybrid nanogenerators. The hybrid nanofiber mats were manufactured using poly(vinylidene fluoride) and thermoplastic polyurethane as the piezoelectric and triboelectric counter materials, respectively, by the simultaneous electrospinning process. Surface-engineering agents such as poly(vinylpyrrolidone), reduced graphene oxide nanoplates (rGO NPs), and zinc oxide nanowires (ZnO NWs) were utilized in three-dimensional decoration stages. The nanofiber surfaces were roughened using the sacrifice method, followed by the application of electrospraying and hydrothermal growth techniques to decorate the nanofibers with rGO NPs and ZnO NWs, thereby enhancing the device. The resulting hybrid nanogenerators were subjected to periodic compression via an applied force, resulting in a 75.0% increase in voltage density and a 169.23% increase in current density compared to the neat hybrid nanogenerator, thanks to the surface roughening treatment. Furthermore, the decorations of rGO NPs and ZnO NWs on the nanofibers contributed to a 271.80% increase in voltage density and a 230.77% increase in current density, reaching values of 2.35 kV/m 2 and 3.40 mA/m 2, respectively. The nanogenerators were also tested in various applications, including energy storage, device powering, and textile sensors, to demonstrate their practicality.