A Polymer Composite as a Thermal Antifuse for Battery-free RFID Temperature Indicators

Time-temperature indicators (TTIs) play an important role in logistics, supply chain, and inventory management. They indicate a visual signal when the temperature exceeds a predefined threshold. However, TTIs require a manual process of checking each label individually, making their applications time and cost-intensive. Radio frequency identification (RFID) tags can streamline the process with data readily available in digital format. Challenges of RFID-based temperature sensors are the need for a battery and incompatibility with standard readers. In this study, thermoresponsive composites are developed based on acetylene black (AB) and poly(ethylene glycol) (PEG). By mixing two PEG binders having different molecular weights, the resulting composites function as thermal antifuses, irreversibly transitioning from a high resistance (HR) state to a low resistance (LR) state. The optimal composition detects a threshold temperature of ≈60 °C and shows a large HR/LR ratio of >10³. Combining the antifuse based on this unique AB/PEG composite with an RFID tag with a tamper detection capability allows the fabrication of a battery-free, passive RFID temperature indicator equipped with a 1-bit non-volatile memory. The device can track the environment of temperature-sensitive items, save the status, and indicate a digital output when a temperature threshold has been exceeded.