Design of Photonic Crystal System for real-time monitoring of cold-chain transportation

Time-temperature indicator (TTI) has been widely used for real-time monitoring of perishable products during cold-chain transportation. However, the existing TTIs struggle to simultaneously achieve broad temperature monitoring ranges and high stability. Temperature-responsive photonic crystal (PC) materials can undergo obvious structural color changes through physical structural transformations. Herein, an ionic liquids (ILs) diffusion-type photonic crystal time-temperature indicator (PC-TTI) is developed. Duration of high-temperature exposure and quality of monitored product can be inferred based on the color change of the PC film. Leveraging the stability and environmental friendliness of polymer materials and ILs, this PC-TTI can achieve irreversible structural color changes. Moreover, by selecting ILs with different melting points, the PC-TTI can adapt to a wide temperature range. Featuring flexible design, simple preparation, high sensitivity, and robust stability, this kind of PC-TTI shows strong potential for real-time temperature monitoring applications in the food cold-chain industry.