Light-induced color changing of redox dyes assisted by a photoinitiator for information encryption on hydrogel paper

Abstract

In this work, we reveal an intriguing mechanism in which free radicals yielded from a commercial cleavage photoinitiator are able to induce rapidly color changing in a methylene blue redox dye under UV irradiation. Leveraging this mechanism, a type of photopolymerized hydrogel rewritable paper through a simple and cost-effective “ink-pumping” strategy for information encryption is proposed. The proposed hydrogel paper exhibits a remarkable ability of transient information encryption and self-erasing decryption (“burn after reading”). Such rewritable paper supports both template-assisted printing and freehand UV writing with stable performance over more than 20 rewrite cycles and a high spatial resolution of up to 3 μm. Moreover, the proposed mechanism and method can be extended to other color redox dyes to produce multi-color patterning. We believe that the proposed mechanism and fabrication strategy open a new pathway for image recording, information storage, rewritable photonic paper, and secure information transmission.