Self-Destructive Structural Color Liquids for Time-Temperature Indicating

Vaccines are undoubtedly a powerfulweapon in our fightagainstglobal pandemics, as demonstrated in the recent COVID-19 case, yetthey often face significant challenges in reliable cold chain transport.Despite extensive efforts to monitor their time-temperaturehistory, current time-temperature indicators (TTIs) sufferfrom limited reliability and stability, such as difficulty in avoidinghuman intervention, inapplicable to subzero temperatures, narrow trackingtemperature ranges, or susceptibility to photobleaching. Herein, wedevelop a class of structural color materials that harnesses dualmerits of fluidic nature and structural color, enabling thermal-triggeredvisible color destruction based on triggering agent-diffusion-inducedirreversible disassembly of liquid colloidal photonic crystals forindicating the time-temperature history of the cold chain transport.These self-destructive structural color liquids (SCLs) exhibit inherentirreversibility, superior sensitivity, tunable self-destructive time(minutes to days), and a wide tracking temperature range (-70to +37 degrees C). Such self-destructive SCLs can be conveniently packagedinto flexible TTIs for monitoring the storage and exposure statusof diverse vaccines via naked-eye inspection or mobilephone scanning. By overcoming the shortcomings inherent in conventionalTTIs and responsive photonic crystals, these self-destructive SCLscan increase their compatibility with cold chain transport and holdpromise for the development and application of the next-generationintelligent TTIs and photonic crystals.