Engineered cellulosic triboelectric materials for multi-modal sensing via β-phase programming

Cellulosic triboelectric materials have gained widespread attention in triboelectric nanogenerators (TENGs) recently due to their fascinating merits of renewability, biodegradability, and low cost. However, cellulose-based TENGs still are challenged by the low surface charge density of triboelectric materials. Herein, the negative charged cellulosic triboelectric materials are functionalized as triboelectric layers for self-powered sensors via an electrostatic spinning method, where the electrospun polyvinylidene fluoride (PVDF) nanofibers fill with the porous air-laid paper (AP), boosting the formation of polar β-phase crystals and a negative shift of the surface potential. The TENG constructed with PVDF/12 wt%@AP affords charge output of 60.7 μC m^-2 and power output of 233.28 mW m^-2, and the as-prepared contact self-sensor presents unparalleled sensitivity of 6.20 V kPa^-1 under pressures from 1.23 kPa to 5.0 kPa. In addition, we design the non-contact self-powered sensor, capable of recognizing different objects and accurately detecting human movements like walking, running, and jumping. Notably, the TENGs can also be used as a wireless sensor terminal for smart devices to provide convenient sensing functions. This β-phase cellulosic materials are a step toward wearable self-powered sensor systems that are durable to capture mechanical energy from the environment.