Controlling Photochromism of Donor‐Acceptor Stenhouse Adducts on Micro‐Dot Arrays Beyond Human‐Eyes Resolution for Dynamic Light Encryption

Conventional photoresponsive materials switch between two static states. Mastering the photoisomerization process expands their potential dynamic applications such as real-time information displaying. Here we demonstrated precise control of the dynamics of solid-state photochromism by introducing a "visual deception" strategy, where a micro-dot array whose individual features are below the resolution limit of the human eyes. This array comprises photochromic and non-photochromic pixels; the former are generated by inkjet-depositing ester-functionalized inks onto surfaces pretreated with donor-acceptor Stenhouse adducts (DASAs). Under constant light irradiation, the photochromic kinetics is monotonically and uniformly increased with the increase of grayscale values, which is defined as the areal ratio of photochromic to total pixels. This fine-tuned manipulation of photochromism enables the development of a dynamic light-encryption technology, where fluorescent information is encoded at multiple grayscale levels using a high-precision nanomaterial deposition inkjet printing system. The encrypted information is temporarily unveiled under steady light irradiation, appearing only within a specific time window. By introducing a temporal dimension to optical security, this technology establishes a new paradigm for advanced anti-counterfeiting and information protection.