A Bending Passive RFID Tag as a Sensor for High-Temperature Exposure

This paper introduces a prototype of a low-energy high-temperature exposure sensor, which is a temperature-sensitive passive UHF RFID tag that bends forward when exposed to warm air. This "Bending Tag"design is based on a simple dipole antenna fabricated from an electro-textile material. The antenna has a 3D-printed substrate, which is constructed from a commercial Thermo Reactive Filament that gets soft when exposed to 50°C for 30 seconds, causing the tag to bend forward and curve. The sensor tag initially has a read range of more than 6 meters throughout the global UHF RFID frequency band. After bending, there is a significant decrease in the read range (to around 2-3 meters), which is caused by the changed backscattered power of the sensor tag. In an office environment, the backscattered power changes from -36 dBm to -43 dBm. The change in a sensor tag-reference tag system as dP% is approximately 70%. Based on these initial results, our bending tag can be further developed to work as a cost-effective low-energy sensor for monitoring high-temperature exposure.