A Battery-Free Temperature Sensor With Liquid Crystal Elastomer Switching Between RFID Chips

Abstract

In this research, we have developed a novel temperature sensor to be utilized in the Cold-Supply-Chain (CSC) for perishable items. This sensor conveys temperature threshold crossings by switching operation between two individual RFID ICs, i.e., two individual Electronic Product Codes (EPCs). The advantage of this sensor compared to other existing technologies is that it can operate passively (i.e., battery-free) through multiple room-to-cold and cold-to-room temperature cycles, in real-time, without requiring any form of resetting. This design utilizes innovative cold-responsive liquid crystal elastomers (LCEs), which change shape when stimulated by cold temperatures and returns to a relaxed state when the stimulus is removed. In fact, this is the first temperature sensor that conveys temperature threshold crossings by switching between two RFID ICs using LCEs. The correct operation of the sensor is validated by RFID measurements. ANSYS HFSS and ANSYS Circuit Designer were used for the simulation analysis. The performance of the proposed design was validated using simulations and measurements.

Keywords

• RFID temperature sensor
• liquid crystal elastomers (LCEs)
• passive RFID
• multi-chip RFID antenna
• bow-tie antenna
• microstrip balun