Preparation and characterization of bacterial cellulose-ZnO piezoelectric nanocomposites studied using Piezoresponse Force Microscopy (PFM)

In this paper, an innovative biodegradable, biocompatible and implantable piezoelectric composite is proposed. Bacterial cellulose (BC) was functionalized by adding piezoelectric ZnO nanoparticles (NPs) obtaining free-standing piezoelectric nanocomposites (BC@ZnO). BC was obtained as a product of the fermentation process by Gluconacetobacter xylinum using food wastes. Composites with 5 to 40 wt% of ZnO in the BC matrix were prepared by stirring fibrillated BC pulp in a ZnO suspension, followed by vacuum filtration. The joint results coming from X-ray diffraction, scanning electron microscopy and Fourier-transform infrared spectroscopy analyses demonstrate the efficacy of the proposed synthesis route to achieve BC@ZnO nanocomposite films. The paper discusses extensively the impact of ZnO content on piezoelectric response by using Piezoresponse Force Microscopy for the first time for BC@ZnO nanocomposites. This characterization has evidenced a 270 % increase in the piezoelectric constant (d33) of pure BC with the addition of ZnO NPs. A maximum filler content was identified to reach the best piezoelectric response beyond which a drastic drop of d33 was measured. This behaviour has been interpreted by considering the co-presence of two competitive mechanisms, connectivity and agglomeration. A trade-off between them is required to maximize the piezoelectric activity.