In this work, we report the superior piezoelectric energy harvester ability of a non-electrically poled Fe-doped reduced graphene oxide (Fe-RGO)/poly(vinylidene fluoride) (PVDF) nanocomposite film prepared through a simple solution casting technique that favors the nucleation and stabilization of ≈99% relative proportion of polar γ-phase. The piezoelectric energy harvester was made with non-electrically poled Fe-RGO/PVDF nanocomposite film that gives an open circuit output voltage and short circuit current up to 5.1 V and 0.254 μA by repetitive human finger imparting. The improvement of the output performance is influenced by the generation of the electroactive polar γ-phase in the PVDF, due to the electrostatic interactions among the -CH2-/-CF2- dipoles of PVDF and the delocalized π-electrons and remaining oxygen functionalities of Fe-doped RGO via ion-dipole and/or hydrogen bonding interactions. Fourier transform infrared spectroscopy (FT-IR) confirmed the nucleation of the polar γ-phase of PVDF by electrostatic interactions and Raman spectroscopy also supported the molecular interactions between the dipoles of PVDF and the Fe-doped RGO nanosheets. In addition, the nanocomposite shows a higher electrical energy density of ≈0.84 J cm(-3) at an electric field of 537 kV cm(-1), which indicates that it is appropriate for energy storage capabilities. Moreover, the surface of the prepared nanocomposite film is electrically conducting and shows an electrical conductivity of ≈3.30 × 10(-3) S cm(-1) at 2 wt% loading of Fe-RGO.

chemical) available in our surrounding, mechanical energy (variable frequency and amplitude) is the most urgent valuable energy because of its greater accessibility anywhere and anytime. [ 1,4 ] Several approaches have been reported to harvest mechanical energy from different mechanical energy sources, such as movement of body (fi nger imparting, pushing, stretching, bending, twisting, etc.), talking, breathing, air fl owing, vibration, friction, water falling, and hydraulic forces (ocean waves, blood fl ow, etc.) to power up various portable electronic devices. [4][5][6][7][8][9][10][11] Thus, human motion based energy harvesting technology is of great interest due to its emergent trends to power up portable smart electronic devices. [ 12,13 ] Recently, piezoelectric nanogenerators (PNGs) and triboelectric nanogenerators (TENGs) have attracted great attention for harvesting mechanical energy under different small mechanical and biomechanical actions with variable amplitude and frequency present in our living environment. [ 12,14 ] Although, TENGs have exhibited high output with high energy conversion efficiency up to ≈55%, they are unfavorable for long term uses (low durability) due to wear and tear at the two contact surfaces and industrial packaging problem in open environment for humidity. [ 15,16 ] Thus, to realize fully independent, scalable, sustainable, and wireless operation of low power-consuming self-powered devices and systems, development of PNGs with large power generating performance, high sensitivity and energy conversion effi ciency, and prominent mechanical durability is highly important. A lot of research works have been reported to fabricate PNGs using various semiconducting nanomaterials, e.g., ZnO, InN, GaN, Te, and lead based Pb(Zr,Ti)O 3 , (PZT) and lead free ceramics (BaTiO 3 , ZnSnO 3 , NaNbO 3 , KNbO 3 ) with superior energy conversion effi ciency. [17][18][19][20][21][22][23][24][25][26] But they have limitations, e.g., brittle, heavy weight, poisonous, low durability compared to piezoelectric polymers which retain their fl exibility and higher strain level to Till date, fabrication of piezoelectric nanogenerator (PNG) with highly durable, high power density, and high energy conversion effi ciency is of great concern. Here a fl exible, sensitive, cost effective hybrid piezoelectric nanogenerator (HPNG) developed by integrating fl exible steel woven fabric electrodes into poly(vinylidene fl uoride) (PVDF)/aluminum oxides decorated reduced graphene oxide (AlO-rGO) nanocomposite fi lm is reported where AlO-rGO acts as nucleating agent for electroactive β-phase formation. The HPNG exhibits reliable energy harvesting performance with high output, fast charging capability, and high durability compared with previously reported PVDF based PNGs. This HPNG is capable for harvesting energy from a variety and easy accessible biomechanical and mechanical energy sources such as, body movements (e.g., hand folding, jogging, heel pressing, and foot striking, etc.) and machine vibration. The HPNG exhib...

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Electronics wastes (e‐wastes) are the major concern in the rapid expansion of smart/wearable/portable electronics in modern high‐tech society. Informal processing and enormous gathering of e‐wastes can lead to adverse human/animal health effects and environmental pollution worldwide. Currently, these issues are a big headache and require the scientific community to develop effective green energy harvesting technologies using biodegradable/biocompatible materials. Piezoelectric/triboelectric nanogenerators (PNGs/TNGs) are considered one of the most promising renewable green energy sources for the conversion of mechanical/biomechanical energies into electricity. However, organic/inorganic material based PNGs/TNGs are very much incompatible, and considered e‐wastes for their non‐biodegradability. This review covers potential uses of biodegradable/biocompatible materials which are wasted every day as nature driven material based bio‐nanogenerators with a particular focus on their applications in flexible PNGs/TNGs fabrication. Structural investigation and possible working principles are described first in order to outline the basic mechanism of bio‐inspired materials behind energy harvesting. Then, energy harvesting abilities and the mechanical sensing of bio‐inspired integrated flexible devices are discussed under various mechanical/biomechanical activities. Finally, their potential applications in various flexible, wearable, and portable electronic fields are demonstrated. These bio‐inspired energy harvesting devices can make huge changes in fields as diverse as portable electronics, in vitro/in vivo biomedical applications, and many more.