UHF RFID humidity sensor tag based on hygroscopic polymeric load

Passive UHF RFID tags, beside item labelling, are also able to exploit capability of sensing the physical state of the tagged object as well as of the surrounding environment. Here a family of polymer-doped tags are proposed and fully characterized for the detection of ambient humidity. A sensitive chemical species based on PEDOT: PSS is used to dope a properly shaped slot carved into a folded-like patch tag. The sensing capabilities of the radio-sensor are investigated by means of measurements for different quantities of sensitive material and in cyclic exposures. The device could have interesting application in the assessment of the air quality in living and controlled rooms, in the monitoring of the conservation state of foods, in the preservation of walls, and even to monitor the healing degree of wounds.