Cellulose and Chitin Twisted Structures: From Nature to Applications

Twisted structures are ubiquitous in plants and animals. Cellulose and chitin are natural polymers that form the structural skeleton of various twisted systems observed across different length scales, ranging from the molecular to the nano, micro, and macro scale. In addition, cellulose and chitin helicoidal structures are found to be responsible for structural coloration, enhanced mechanical properties, and motion. This review first addresses cellulose and chitin-based chiral molecular systems and nanoscale helicoidal arrangements. Attention is given to cellulose nanocrystals, water interactions, out-of-equilibrium structural colorful structures formed by cellulose derivatives, and chitin's optical and mechanical properties. The discussion progresses to the micro and millimeter scales, where specific examples are presented to showcase specialized helical cellulose-based organizations. The chosen examples illustrate the formation of different helicities, adaptative shapes, and movements at varying length scales, such as in vascular leaf petioles at the micro-scale and millimeter-scale in tendrils and awns of Erodium fruits. So far, the results indicate that significant work should be done on out-of-equilibrium systems. In addition, much must be learned from nature to produce novel twisted functional materials. This work aims to provide a comprehensive overview of the state-of-the-art study of twisted cellulose and chitin-based structures and their potential applications.