Reversible optical data storage and encryption enabled by phase-change and hydrogel integration

Phase-change materials and hydrogels, which are emerging as versatile, low-cost, high-speed materials with large-area processing capabilities, are key building blocks for next-generation optical information storage and multi-level encryption. Here, we introduce a hybrid platform that synergistically integrates directly laser-written antimony trisulfide (Sb₂S₃) with a humidity-responsive azido-grafted carboxymethyl cellulose (CMC-N₃) hydrogel, enabling the fabrication of a full-color image multiplexing. The Sb₂S₃ medium layer enables non-volatile, rewritable optical data via laser-induced amorphous-crystalline transitions, while the hydrogel introduces UV-programmable cavity modulation for data writing and consequently, achieving a humidity-dependent tunable full-color image response. Together, these dynamic and reversible processes enable independent encoding and retrieval of multi-level information, resulting in a transmissive multiplexed optical storage device. This multi-programmable layer approach establishes a new paradigm for multifunctional optical devices, unlocking opportunities in secure data storage, anti-counterfeiting displays, and environmental sensing.