Advances in bioinspired and multifunctional biomaterials made from chiral cellulose nanocrystals

Constructing and mimicking bioinspired structural color from bio-based materials has aroused tremendous attention. Cellulose nanocrystals (CNC), a typical nanomaterial made from lignocellulosic biomass, have been explored for the preparation of photonic materials. Structural color can be controllably achieved via incorporating different types of substances into CNC, which not only improves its mechanical properties but also adds new multifunctional properties. Herein, we provide a systematic summary of the following topics: 1) preparation of chiral cellulose nanocrystals, the iridescent mechanism of chiral CNC film, and the fundamentals of CNC suspensions on structural color formation; 2) construction of CNC-based composites with structural color by incorporating effective materials; and 3) potential applications of CNC-based composites in environment, advanced encryption, biomedicine, soft actuators, and energy storage. While numerous reviews on CNCs have appeared in the literature, there is still a lack of a comprehensive summary of the state-of-the-art on the preparation, iridescent mechanism, and applications of CNC-based composites, especially with regard to some advanced applications such as actuators and energy storage. To the best of our knowledge, this review represents a comprehensive and systematic description of the advances in bioinspired and multifunctional biomaterials from chiral CNC, and is believed to provide sufficient reference value for related aspects and promote the application of novel CNC-based composites in emerging areas.