Passive Monitoring of Water Evaporation in Textile Fabrics for Industrial Applications Using a Battery-Free UHF RFID Tag

This paper presents a low-cost, battery-free antenna-based sensor (ABS) method for monitoring fabric drying using Ultra High Frequency (UHF) Radio Frequency Identification (RFID) technology. As part of the Industry 4.0 trend, the presented method offers a scalable and energy-efficient sensing solution for real-time data collection and process optimization in smart manufacturing environments. The proposed tag design combines a self-tuning integrated circuit (IC) with an absorbent textile material acting as a liquid container. The system exploits variations in the complex dielectric permittivity caused by the evaporation of the liquid in the tag antenna substrate to produce changes in the IC Sensor Code (SC). Several experiments are conducted on three different textile substrates: denim, polyester, and cotton, and the sensor performance is evaluated with respect to a physical model of liquid mass evaporation. The experimental results validate the sensor precision and repeatability over different realizations achieving a percentage mean absolute error ( ${\mathrm {MAE}}_{\%}$ ) below 10% across all tested materials. A gravimetric measurement is performed on a large textile sample to define a calibration procedure for the sensor. The results highlight the potential of passive UHF RFID sensors for monitoring humectation and evaporation processes in the textile industry.