Photonic crystal-based structural color switches

Photonic crystals (PCs), a class of advanced optical metamaterials, have garnered considerable attention in the scientific community due to their versatile structural configurations and precisely tunable photonic stop band (PSB) properties. Unlike traditional stimuli-responsive PCs, PC-based structural color switches exhibit exceptional capabilities in modulating between colored and non-colored states in response to external stimuli, offering significant potential for advanced optical applications. Despite growing interest in this field, systematic reviews comprehensively addressing the fundamental mechanisms governing structural color switching and their practical implementation remain scarce. This review systematically classifies color-changing strategies of PC-based structural color switches into four fundamental approaches, including the modulation of ordered/disordered state transitions, PSB position modulation, refractive index matching modulation, and optical path direction modulation. By establishing a basic mechanistic analysis framework, we comprehensively summarize specific scientific research practices of PC-based structural color switches under various stimulus-responsive behaviors, including responses to electric fields, magnetic fields, solvents, temperature, light, viewing angles, and stress. Then, the practical applications of these systems in sensors, anti-counterfeiting, and display are thoroughly discussed. Finally, we address the current challenges and prospects in this field, proposing several potential functional architectures and promising applications. PC-based structural color switches are poised to serve as a transformative technology, enabling breakthroughs across multiple scientific disciplines and catalyzing innovation in various industrial sectors.