부산대학교 도서관

An autonomous and continuously operating Radio Frequency Identification (RFID) temperature sensor is designed, manufactured, and tested. This sensor is battery-free and can detect temperature threshold crossings for multiple (room-to-cold and cold-to-room) temperature cycles, respectively. The proposed sensor conveys temperature threshold crossings through the controlled switching of its operating frequency within the 902–928 MHz Ultra High Frequency (UHF) RFID band. For the first time, shape morphing cold-temperature reactive Liquid Crystal Elastomers (LCEs), which provide reversible actuation, are utilized. The proposed sensor design consists of a patch antenna with a customized slot. A passive mechanical switch is connected across this slot and provides the frequency switching as it is activated and deactivated. The integration of this switch with the antenna is achieved using a co-simulation method. Furthermore, the cold-temperature reactive LCE triggers the switch when a temperature violation has occurred, thereby switching the operating frequency of the sensor based on temperature changes. Additionally, a high-dielectric constant substrate and a single matching network that operates at two discrete frequencies are used to design our compact frequency-domain temperature sensor. Moreover, based on the RFID platform, this sensor operates effectively in close-proximity to other sensors. Also, is provides identification and temperature information through an autonomous, continuous, and cost-effective design. Therefore, the proposed sensor has the potential for operation in the Internet of Things (IoTs) applications, where large amounts of data is collected from numerous sensors to extract valuable information for the benefit of users, manufacturers, and delivery companies in the virtual domain of the internet. Finally, ANSYS HFSS and Circuit Designer are used for the simulation modeling. The performance of our sensor is validated using measurements and simulations that agree very well.