Bio‐Inspired Cholesteric Phase Cellulose Composite with Thermochromic and Circularly Polarized Structural Color for Multilevel Encryption

The escalating need for enhanced cryptographic security necessitates the development of advanced materials designed for the secure storage and transmission of information. Drawing inspiration from the unique color‐altering and polarizing capabilities of beetles, this work develops a transparent, thermochromic, and circularly polarized cholesteric phase cellulose composite (CPCC). This is achieved by integrating self‐assembled hydroxypropyl cellulose with cholesteric liquid crystal (CLC) structure in tandem with a crosslinked poly(N‐isopropyl acrylamide) (PNIPAM) network. The crosslinking density impacts the response degree of thermochromism, which can be regulated by modifying the UV exposure time during PNIPAM production. The CLC structure in CPCC uniquely results in reflected right circularly polarized light. When coupled with waveplates, this mechanism inverts the rotation direction of the reflected light, creating orthogonal structural colors of different brightness levels under left and right circularly polarized light. The excellent transparency of CPCC facilitates seamless integration with the environment, offering optimal camouflage. Sophisticated techniques, such as color coding and Morse coding, can further be incorporated within the CPCC to increase encryption security and the complexity of decryption. Collectively, the CPCC's transparency, thermochromism, and chirality present significant potential in the design and development of materials for high‐security information encryption, contributing valuable insights to the field.