Detecting Breaks in Cold Chain Integrity Using Chipless RFID Time–Temperature Sensors

This article presents a low-cost, food-safe chipless radio-frequency identification (RFID) time–temperature (TT) sensor that operates in the 3–5 GHz [ultra wide band (UWB)] band. The sensor is capable of detecting three types of TT exposure events typically found in cold chain operations. We achieve this by interfacing a chipless RFID tag with three cooking oils having melting points of 14.2 °C, 17.3 °C, and 23.6 °C, respectively. The three TT events induce unique changes in the oil phase (solid to liquid) for all three oil types and this manifests as distinct signal responses from the chipless RFID tag. We discuss how logistic providers can infer TT exposure data at key steps in the cold chain via quantitative data obtained from these responses. Planned sensor improvements and future research directions are also discussed.