A Review of Advanced Processing Technologies for Birefringent Cellulosic Anti‐Counterfeiting Materials

Abstract Nanocellulose (NCs), the most abundant natural resource, has birefringence when aligned in order, and the resulting materials are of unique optical properties, showing great potential in sustainable anti‐counterfeiting. However, the difficulty in processing, due to the strong hydrogen‐bond interactions between hydroxyl groups, places severe restrictions on the application of NCs. Nowadays, many efforts have been devoted to addressing this problem and there are various novel processing technologies, such as phase transition‐induced self‐assembly, 3D printing, in situ curing of oriented hydrogel, and advanced melt‐processing. Cellulose nanocrystal is taken as the typical example in this review to introduce advanced processing technologies for cellulosic anti‐counterfeiting materials, given its outstanding birefringent characteristic than other NCs. In this review, the trends, challenges, and solutions in the processing of cellulosic anti‐counterfeiting materials are included, focusing on their design mechanism and fabricating strategy. Finally, application prospects and perspectives for the development of green processing technologies with extensive production scale are presented.