The Possibilities of Embroidered Passive UHF RFID Textile Tags as Wearable Moisture Sensors

Moisture measurements of the body can be used for healthcare purposes as well as for helping in exercising. In this paper, the suitability of passive UHF RFID technology for moisture sensing is investigated. The technology has a great potential in wearable, comfortable, and wireless moisture sensing systems, although it is not originally used for sensing purposes. In our study, the tag antenna outlines are embroidered on a fabric substrate, the tag ICs are attached by embroidery or with conductive glue, and the tag performance as a moisture sensor is evaluated by wireless measurements. All tags attained peak read ranges of about 7-8 meters, which is well enough for wireless moisture sensors. The effects of moisture on the tag response were noticeable through a frequency range of 900-980 MHz and the tag performance was excellent also when wet. Thus, the achieved results indicate high potential of passive UHF RFID textile tags in moisture sensing and embroidery as a textile tag antenna and antenna-IC interconnection fabrication method.