3D printed micro-structured hydrogel device with transmittance-changeable soft ‘armor’ camouflage for dual-encryption

Hydrogel-based physical dual-encryption typically relies on the reversible shape-deformation of polymer chains for the decryption. However, the stored information is confronted by indecipherability at the microscale because the intrinsic relaxation of polymer chains would disrupt the fidelity of encoded information. Inspired by female Doryteuthis opalescens squid’s camouflage strategy (i.e. , switching a stripe on its mantle from nearly transparent to opaque white), we devised a reversible transmittance-changeable hydrogel layer to fully cover the mono-encrypted information layer for dual-encryption. The micro-structured hydrogel was manufactured via 3D printing to encode the information, which can be decoded by UV-induced fluorescent emission. Then, the white camouflage hydrogel was constructed to conceal the mono-encrypted layer, which will not affect the information encoding layer during the reversible polymer chain mobility. The information can be decoded with alkaline solution and UV irradiation in a rapid speed, i.e. , in 4 min, with good reusability. Moreover, the information was accurately unveiled even at microscale resolution, holding great promise for high-level encryption at the device level.