Wireless Temperature Monitoring With Shape Memory Alloy-Based Antenna

Economical sensing and recording of temperature are important in the transportation and management of fragile goods such as medicine, fish/poultry, and other temperature-sensitive items. Existing approaches measure the entire temperature profile using electronic devices running on a continuous power source. This letter presents a simple, intelligent, and battery-free solution for capturing interesting temperature events using the natural thermomechanical state of a shape memory alloy (SMA). Our approach utilizes the temperature variation induced irreversible configuration of SMA, which provides a natural ability to capture the temperature history without the need for electronic data logging. In this letter, SMA is used to record the threshold temperature violation event. A prototype antenna is shown to monitor the temperature at 30°C with a ±1°C error. A difference of 17 dB in frequency response was observed with and without temperature violation. Detailed design and experimental studies have been performed to validate the proposed approach.