Preparation of chitosan-based films loaded with ZnO nanoparticles for piezoelectric energy harvesting

Abstract

The growing demand for portable electronics and self-powered systems has intensified the search for sustainable energy harvesting solutions. Piezoelectric nanogenerators are promising, yet their reliance on non-biodegradable materials contributes to electronic waste, highlighting the need for efficient and greener alternatives. This study proposes a novel bio-based piezoelectric film composed of chitosan (Ch); glycerol (G) loaded with different concentrations of zinc oxide nanoparticles (ZnO NPs) to enhance the piezoelectric response. The resulting films were thoroughly characterized, demonstrating the successful incorporation of ZnO NPs by FTIR. Changes in the film's morphology as well as NPs sizes (ranging between 40.5 and 44.05 nm), aggregation percentage (14–26%) and distribution were observed by FESEM. Contact angle data revealed changes (from 97.0° to 104.5°) in surface wettability due to the presence of ZnO NPs. Thermogravimetric analysis and differential scanning calorimetry indicated a dose dependence in terms of the thermal behaviour and stability of different films; whereas XRD confirmed the presence of the crystalline wurtzite structure of ZnO NPs. Piezoelectric performance was evaluated by subjecting the films to mechanical impacts using a calibrated modal hammer, reaching values of about 6.21 mV/N for ChG 2.5. The results demonstrated that the proposed biodegradable films exhibit great potential as eco-friendly energy harvesters for flexible and wearable electronics. It is worth mentioning that the combination of biopolymer-plasticizer-ZnO NPs has not been previously explored for this purpose. Hence, this work contributes to the growing field of sustainable nanogenerators and lays the groundwork for future development of biopolymer-based piezoelectric devices.