Emerging cellulosic materials for sustainable mechanosensing and energy harvesting devices: Advances and prospect

Triboelectric nanogenerators (TENGs), as promising energy-generating devices, have paved the way for efficient energy collection at the micro-nanoscale since their inception in 2012. TENG technology can convert low-frequency, irregular minor dynamic mechanical motions into usable electrical energy, serving the dual purposes of mechanosensing and energy harvesting. Cellulose, a common biomacromolecule widely found in plants, emerges as a promising candidate for the development of versatile TENG devices due to its abundance of highly polar hydroxyl groups (-OH), which can be easily chemically modified and structurally processed. This review emphasizes the distinctive hierarchical structure of cellulose mainly extracted from wood cell walls, presenting it as macromolecular chains, nanofibers, nanosheets, and other aggregates based on the deciphering of wood cell walls. Leveraging their favorable properties of renewability, biodegradability, biocompatibility, and processability, various cellulose-based materials, including films, aerogels, hydrogels, and ionogels, are manufactured with controlled flexibility, polarity, conductivity, specific surface area, and mechanical resilience. Subsequently, the inherent capability and intrinsic mechanisms of these cellulose-based materials in electron donation and acceptance are discussed, culminating in proposed optimization strategies for the modification of cellulosic triboelectric friction materials and device configuration aimed at enhancing the surface charge density of TENGs. The potential benefits and challenges of using cellulose-based TENGs for mechanosensing and energy harvesting are also presented and discussed in detail.