Enhanced Flexoelectricity in Barium Titanate-Cellulose Composite Thin Films

Biopolymers, the potential flexoelectric materials, are environment-friendly, degradable, lightweight, cost-effective, and possess remarkable processing properties catering to the requirements of advanced devices. However, the flexoelectric coefficient of biopolymers is normally much weaker than that of ceramic materials, limiting their potential applications for designing high-performance green electromechanical coupling devices. To improve the flexoelectric response in biopolymers, we composited barium titanate (BTO) with 2,2,6,6-tetramethylpiperidine-1-oxyl -oxidized cellulose nanofibrils (TOCNF) to enhance the flexoelectric response of TOCNF. Owing to the high permittivity and flexoelectric effect of BTO, the relative dielectric constant and flexoelectric coefficient of 33.3 wt% BTO-TOCNF films reached 30.94 @ 1 kHz and 50.05 ± 1.88 nC/m @ 1 Hz, which were almost 172 times and 27 times higher than those of TOCNF, respectively. The composite thin film contains high dielectric constant and flexoelectric coefficient, as well as excellent flexibility. Our study provided a straightforward and efficient method for improving the flexoelectric effect of biopolymers, and demonstrated its great potential applications in flexoelectric-based devices.