Development of disposable paper-based smart visual labels with thermochromic materials for cold chain temperature (−18 °C) monitoring

Monitoring cold chain temperatures is essential for ensuring the safety of food, the efficacy of drugs, and the stability of vaccines. However, existing methods face challenges, including the lack of real-time monitoring, concerns over data accuracy, and environmental interference. To resolve these challenges, a kind of thermochromic materials (TCMs) was developed to undergo phase changes above a specific threshold of −18 °C. These TCMs were synthesized with a precise mass ratio of organic solvents, comprising 96 % undecane and 4 % n-dodecanol. The TCMs were applied as coatings on paper to generate Quick Response (QR) codes, intended for identifying real-time temperature fluctuations. Exposure to temperatures exceeding −18 °C for an extended period induced fading and blurring in QR code patterns, rendering them unrecognizable even upon reversion to −18 °C or below. The visual response system can be employed for dynamic, intelligent temperature monitoring within cold chain logistics.