Harnessing molecular isomerization in polymer gels for sequential logic encryption and anticounterfeiting.

Using smart photochromic and luminescent tissues in camouflage/cloaking of natural creatures has inspired efforts to develop synthetic stimuli-responsive materials for data encryption and anticounterfeiting. Although many optical data-encryption materials have been reported, they generally require only one or a simple combination of few stimuli for decryptions and rarely offer output corruptibility that prevents trial-and-error attacks. Here, we report a series of multiresponsive donor-acceptor Stenhouse adducts (DASAs) with unprecedented switching behavior and controlled reversibility via diamine conformational locking and substrate free-volume engineering and their capability of sequential logic encryption (SLE). Being analogous to the digital circuits, the output of DASA gel-based data-encryption system depends not only on the present input stimulus but also on the sequence of past inputs. Incorrect inputs/sequences generate substantial fake information and lead attackers to the point of no return. This work offers new design concepts for advanced data-encryption materials that operate via SLE, paving the path toward advanced encryptions beyond digital circuit approaches.