Recent advances in structural color display of cellulose nanocrystal materials

l Cellulose nanocrystal suspension has the property of self-assembly to cholesteric phase. l The film with cholesteric phase retained after drying can show structural color. l The structural color of nanocellulose-based composite film can change in response to environmental conditions. l The structural color control of film can be realized through the design of microstructure. Cellulose is the most abundant and renewable polymer resource in the biosphere and is characterized by low cost, non-toxicity, and biodegradability. As suspensions can form chiral nematic liquid crystals of the nanometer scale, nanocellulose can exhibit structural color as a film via self-assembly or microstructure formation. Structural color is a type of gloss caused by the action of light waves and is widely observed in nature. In this review, the effects of various factors involved in the preparation of nanocellulose films on structural color, the color response of the nanocellulose films to environmental factors, and the structural design of cellulose nanomaterials in the field of color development are summarized. Advances in the field of structural coloration of nanocellulose materials in recent years are described. Finally, future developments anticipated in nanocellulose material structure color are discussed. As an increasing number of countries have started to ban disposable plastics, cellulose-based materials as biodegradable alternatives will be the subject of more extensive research, and the structural color of cellulose nanomaterials will become one of the key parameters in various applications.