Progress in photonic crystal materials for rewritable paper: insights from recent developments

As a crucial traditional information carrier in human civilization, paper exhibits increasingly significant environmental burdens associated with its manufacturing and recycling processes, prompting exploration into novel paper solutions. Although various materials have been employed to develop rewritable paper, challenges such as chemical toxicity and inadequate color retention frequently remain. Novel rewritable paper with dual advantages of environmental friendliness and long-term color stability is essential. Photonic paper is a type of functional information medium that employs the structural color of photonic crystals as its chromic unit. By integrating stimuli-responsive materials, it achieves a reversible modulation of its photonic bandgap in response to external stimuli. This mechanism enables the complete cycle of information writing, reading, erasing, and rewriting. This review systematically summarizes the fabrication strategies of responsive photonic crystals and the distinct response mechanisms of rewritable photonic paper. It surveys key methods, including capillary force-driven vertical deposition, evaporation-induced self-assembly, and external field-assisted assembly, and details chromogenic processes under various stimuli. Finally, we discuss prospects and challenges, highlighting the potential of this technology as a versatile platform for information encryption and interactive displays through the synergy of structural color and stimulus responsiveness.