Gonçalves, RicardoRima, SergiMagueta, RobertoPinho, PedroCollado, AnaGeorgiadis, ApostolosHester, JimmyCarvalho, Nuno BorgesTentzeris, Manos M.2016-02-262016-02-262015-12GONÇALVES, Ricardo; [et al.] - RFID-based wireless passive sensors utilizing cork materials. IEEE Sensors Journal. ISSN. 1530-437X. Vol. 15, N.º 12 (2015), pp. 7242-72511530-437X1558-1748http://hdl.handle.net/10400.21/5751This paper presents the design of low-cost, conformal UHF antennas and RFID tags on two types of cork substrates: 1) natural cork and 2) agglomerate cork. Such RFID tags find an application in wine bottle and barrel identification, and in addition, they are suitable for numerous antenna-based sensing applications. This paper includes the high-frequency characterization of the selected cork substrates considering the anisotropic behavior of such materials. In addition, the variation of their permittivity values as a function of the humidity is also verified. As a proof-of-concept demonstration, three conformal RFID tags have been implemented on cork, and their performance has been evaluated using both a commercial Alien ALR8800 reader and an in-house measurement setup. The reading of all tags has been checked, and a satisfactory performance has been verified, with reading ranges spanning from 0.3 to 6 m. In addition, this paper discusses how inkjet printing can be applied to cork surfaces, and an RFID tag printed on cork is used as a humidity sensor. Its performance is tested under different humidity conditions, and a good range in excess of 3 m has been achieved, allied to a good sensitivity obtained with a shift of >5 dB in threshold power of the tag for different humid conditions.engUHF RFIDCork characterizationPassive sensorHumidity sensorWireless sensorInkjet printingjournal article10.1109/JSEN.2015.2472980