A new type of TTI based on an electrochemical pseudo transistor

Conventional time-temperature indicators (TTIs) are usually based on various processes, such as the diffusion of colorful solution, color-changing polymerization, enzymatic reactions, and photochromic reactions. In this study, a new type of device based on an electrochemical pseudo-transistor in structured conductive polymers is presented as a TTI with the activation energy closed to results in other studies and products in market. This TTI provides basic functions, such as clock, temperature sensor, and electrical switch. Furthermore, this pseudo-transistor-TTI is combined with radio frequency identification (RFID) technique for the first time. A TTI-RFID label can offer double protection for perishable food by using TTI and RFID readers. This label not only demonstrates that structured conductive polymers can be used as a powerful TTI with an electrical switch but also supplies a new alternative strategy to combine TTI with an RFID tag to supervise and trace the safety of perishable food.