Recent advances of 3D printed functional materials based on plant-derived nanocelluloses: A review

Additive manufacturing (i.e., 3D printing) is regarded as a groundbreaking technology in advanced manufacturing, having developed rapidly in recent years and advancing towards a greener and more sustainable direction. As the dominant polysaccharides in Earth's natural environment, plant-derived celluloses and their products have been widely utilized in various fields, among which the nanocelluloses offer advantages of excellent mechanical performances, desirable processabilities, and environmental friendliness. The evolution of materials science coupled with 3D printing, has facilitated multiple additive manufacturing approaches to produce nanocellulose-based materials, achieving remarkable breakthroughs. This review systematically summarized the latest research progress of 3D printed functional materials derived from plant-derived nanocellulose. The intrinsic structural differences between cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) were elaborated, as well as their mainstream extraction and fibrillation strategies. The compatibility matching mechanisms between two types of nanocellulose and typical 3D printing processes were comprehensively analyzed, focusing on how nanocellulose regulated ink rheology, forming accuracy and post-printing performance. Furthermore, multi-scenario functional applications of these printed materials were discussed covering biomedical materials, energy materials, flexible sensors, food packaging and monitoring materials, etc. Finally, the prominent bottlenecks restricting industrial translation were clarified, including high production cost, poor batch stability, ink agglomeration and limited printing precision, and targeted solutions and future research directions were proposed to facilitate the large-scale development of eco-friendly nanocellulose 3D printing systems.