Preparation Techniques, Design Strategies of Responsive Photonic Crystals and Their Typical Applications in the Field of Sensing

Responsive photonic crystals, as a class of intelligent photonic materials that can generate optical signals in response to external stimuli including temperature, pH, humidity, electric fields, magnetic fields, and specific molecules, exhibit great application potential in sensing and detection, drug delivery, environmental monitoring, and other fields. This is attributed to their unique tunable photonic band gaps and visual sensing characteristics. In this paper, we systematically review the main preparation methods, including the sol–gel method, photolithography, electrochemical deposition, self-assembly, and 3D printing, and compare the advantages and limitations of each method in terms of key performance indicators, cost, applicable material systems, and scalability for large-scale production. The design strategies of photonic crystals based on different response mechanisms are discussed in detail, revealing the structure–activity relationship between external stimuli and the modulation of photonic band gaps. Meanwhile, the typical applications of responsive photonic crystals in the sensing field are comprehensively summarized, with an emphasis on the latest advances in biomedical sensing, environmental monitoring, and intelligent detection. Finally, in view of the current challenges facing responsive photonic crystals, future development directions are prospected, which provides a reference for promoting the translation of responsive photonic crystals from laboratory research to industrial applications.