Facile fabrication of encryption composite materials with trilayer quasi-amorphous heterostructure

Encryption materials represent a major direction of information security, but it is challenging to realize the ideal security combining the complete hiding of complex coding, stability in transmission, camouflage, and reliable decoding. Herein, we report an innovative strategy for rationally constructing encryption composite materials with high security and portability. Compared with common colloidal photonic watermarks, our encrypted optical devices are composed of thermoplastic polyurethanes (TPU) protective layers, polystyrene (PS) switching layers and a CdS coding layer. The optical shielding properties and phase state transition of PS layers enable high-level encoding and decoding security through thermal activation of light transmittance control. Meanwhile, the CdS layer can be clearly revealed in decoding mode because of the high refractive index. Besides, the confinement protection of integrated TPU films prevents the trilayer quasi-amorphous heterostructure from damage. To establish the practical advantage, portable information carriers can be prepared for camouflage. Accordingly, the reliable encoding and decoding system, and ability to integrate with easy-to-carry products, make our composites a potentially high-security encryption device for anti-fraud technology.