Programmable Multifunctional Gels with On-Demand Patterning Capability toward Hierarchical and Multi-Dimensional Encryption and Anti-Counterfeiting.

Hydrogels capable of optical switching have recently become one of the most celebrated materials for information encryption and anti-counterfeiting. However, challenges still remain for developing versatile gel-based platforms with on-demand multistage patterning and multi-dimensional encryption capacities as well as long-term stability. Herein, elaborately designed programmable and multifunctional gels with fascinating anti-swelling (swelling ratios < 0.1%), anti-freezing (below -70 °C), and anti-dehydration (over 3 months) abilities, solvent-induced reversible transparence variations, adjustable fluorescence, self-healing (86% in stress and 94% in strain), Fe-ethylenediaminetetraacetic acid disodium (EDTA·2Na)-induced reversible shape memory, and fluorescence off/on switch capabilities are facilely fabricated based on glycidyl methacrylate functionalized graphene quantum dots and Al cross-linked gelatin and polyacrylic acid. Employing a simple mask photopolymerization or welding technique, various patterns can be readily and hierarchically encrypted on-demand into a single gel label, which can be further fixed into complex multi-dimensional architectures while quenching fluorescence after the treatment with Fe to achieve high-security-level information encryption originating from the synergistic effects of the above multifunctions. The encrypted multi-level information can only be stepwise decrypted by an authorized individual who has mastered all decryption keys. Therefore, the creative design strategy for programing multifunctional gels opens up the possibility for hierarchical and multi-dimensional information encryption and anti-counterfeiting.