Achieving low energy consuming bio-based piezoelectric nanogenerators via modulating the inner layer thickness for a highly sensitive pedometer

Considering their drawbacks of environmental pollution, biodegradable cellulose-based materials are becoming one of the most promising alternative candidates for conventional petroleum-based polymers, which are considered the fundamental materials for dynamical units in human-machine interaction systems. Using an up-to-date hydrogen bond replacement strategy, which means using the highly electronegative F⁻ in polyvinylidene fluoride (PVDF) to replace the intramolecular hydrogen bonds in cellulose for weakening the self-assembly behavior, herein, multilayer-structured piezoelectric nanogenerators (PENGs) composed of cellulose, a small amount of PVDF, and Ba_0.7Ca_0.3Zr_0.2Ti_0.8O₃ (BCZT) fillers were fabricated via modified tape-casting technology. Due to the hydrogen bond network, which was confirmed using multiple characterization methods, the fillers dispersed uniformly in the matrix. Through changing the inner layer thickness, the output performance of the PENGs can be subtly modulated, which is revealed to be caused by the synergistic effect between the trapped electrons and the inter-squeezing between adjacent particles by employing the band theory. When applied to a pedometer, one of the essential devices for monitoring human health, such a modulation can significantly improve its sensitivity. The water contact angle test also indicates their potential for use in humid environments. Compared with some typical cellulose-based PENGs, our device shows outstanding performance in P_D/F, defined as the power density triggered by unit force, indicating our PENG's low energy consumption characteristic.