The morphology effect of embedded ZnO particles-based composite on flexible hybrid piezoelectric triboelectric nanogenerators for harvesting biomechanical energy

Harvesting mechanical energy with a flexible and weightless device for self-power electronics has attracted many interests, nowadays. Hybrid nanogenerators by combining different power generating techniques enhance the performance of nanogenerators. Zinc oxide as a non-toxic ceramic has significant piezoelectric properties. In this paper, piezo/triboelectric hybrid nanogenerators based on three different shapes of ZnO nanoparticles are fabricated. The impact of the ellipse, rod, and pyramid-shaped ZnO particles encapsulated in PDMS matrix on the hybrid nanogenerators performance is investigated. XRD analysis shows pyramid-shaped ZnO particles have more crystals in the c-axis direction which is the piezoelectric effect direction in ZnO material. SEM results show the average size of particles from biggest to the smallest is rod, pyramid, and ellipse shapes, respectively. The maximum open-circuit voltage and short-circuit current are obtained from the pyramid and ellipse-shaped ZnO particle/PDMS composite hybrid nanogenerators with the value of 161 V and 29.8 μA, respectively. The maximum power density of the ellipse, rod, and pyramid-shaped ZnO particle/ PDMS composite-based hybrid nanogenerators is about 1.04, 0.75, and 0.6 Wm −2 , respectively, occurred at 10 MΩ load resistance. In addition, different capacitors are charged by proposed nanogenerators demonstrating the PDMS embedded pyramid-shaped ZnO particles nanogenerator produced greater voltages in the capacitances. Consequently, the hybrid nanogenerators based on the ellipse and pyramid-shaped ZnO particle/ PDMS composites have better performances due to the structure and morphology properties of piezoelectric ZnO particles and can be utilized for the power source of milliwatt flexible portable devices. Graphical Abstract Highlights Harvesting mechanical energy device for self-power electronics has attracted many interests. The impact of three different shapes of ZnO particles encapsulated in the PDMS matrix on the performance of piezo/triboelectric hybrid nanogenerators was investigated. Results demonstrated the maximum current and voltage values occurred in 2.5 wt.% wight ratio of ZnO particles in the PDMS matrix. The maximum voltages obtained from HNGs based on the ellipse, rod, and pyramid-shaped ZnO particles were about 11.95, 10.6 and 16.1V. The maximum power density under load resistance generated by the ellipse, rod, and pyramid-shaped ZnO particle composite-based HNGs was about 1.04, 0.75, an