Light‐Writing and Projecting Multicolor Fluorescent Hydrogels for On‐Demand Information Display

Intelligent rewritable display systems have been long expected to reduce the heavy consumption of single-use or transient devices in the age of Internet-of-Things. However, it remains challenging to construct such systems with integrated functionality of remote control, rapid activation, multicolor and multimode display. Herein, by learning from the unique multilayer arrangement of chromatophores in chameleon skins, a promising kind of rewritable hydrogel multicolor systems is presented that can combine the merits of near-infrared (NIR) light-writing and projecting modes for on-demand information display. Specifically, the systems have typical multilayer layout consisting of poly(dimethylsiloxane) (PDMS)-sealed carbon nanotubes (CNTs) film as photothermal control unit and embedded fluorescent hydrogels as multicolor display unit, in which thermoresponsive hydrogel is constrained within non-responsive hydrogel. Such rational structure design results in the establishment of one promising display mechanism via the cascading "light trigger-heat generation-fluorescence output" process. On this basis, rapid and reversible hand-written display of arbitrary information is achieved within 5 s. Also, sustainable light-projecting display of predesigned multicolor patterns is demonstrated due to the multilayer design that ensures easy patterning of photothermal control or hydrogel display layer. This study brings functional-integrated merits for novel rewritable display systems and open new possibility to construct high-end products for information display/transmission.