High performance and flexible piezoelectric composite incorporating zinc oxide grown on the oxidized nanocellulose by two-step hydrothermal process

While the existed researches about cellulose based piezoelectric composite focused on the direct growth of ZnO on surface of cellulose based paper or membrane, this paper reports a ZnO based piezoelectric composite fabricated by growing ZnO in the cellulose nanofibril (CNF) dispersion substrate via two-step hydrothermal synthesis. After CNF was controllably oxidized to endow with appropriate carboxyl groups and size, it was used as a template and dispersant for in-situ polymerization of ZnO to be CNF@ZnO. Zn2+ is preferentially fixed on the scattered CNF for its active hydroxyl and carboxyl groups which serve as a uniform nucleation for the self-assembly of ZnO, so that it has a preferential orientation with optimal phase structure, one-dimensional rod-like structure, excellent dispersity, low interface energy and interfacial compatibility. Thus the assembled 4CNF/4CNF@ZnO composite membrane has a large elevation in the dielectric properties and piezoelectric performance. Moreover, the 4CNF/CNF@ZnO piezoelectric composite vacuum-impregnated with PDMS exhibits better piezoelectric performance with the open-circuit voltage as high as 25.6 V and the short-circuit current of 1100 nA. It can supply to light LED and has high sensitivity to body movement, indicating its great potential in pressure sensors and generators.