4.1 Functionalized wood composites for vibration sensing

Every running machine and infrastructure produces vibrations with a unique vibration frequency. These vibration frequencies change under external stimuli or malfunction, and their analyses can indicate the health of a machine or infrastructure. Piezoelectric nanogenerators (PENGs) can utilize mechanical energy from vibrations converting it to electricity and act as a self-powered vibration sensor. The current focus for the choice of materials for vibration sensors is towards bio-derived and sustainable piezoelectric materials. Wood is a highly abundant and renewable material, which exhibits weak piezoelectricity due to crystalline native cellulose. A simple delignification treatment improved piezoelectric properties due to increased cellulose content. Further, we prepared functionalized wood with mild chemical treatments while persevering cellulose in its native state to access the wood microstructure at the fibril level. The functionalizations helped to improve piezoelectricity by increased polarity and effective utilization of wood fibrils for a self-powered vibration sensor.