Fully printed CPW-based microwave humidity sensor in phase shifting paradigm

This paper presents a printed microwave humidity sensor with an original sensing principle in phase shifting para- digm, derived from the combination of slots, transmission lines and printing technologies. A composite film made of polypyrrole and TEMPO oxidized cellulose nanofibers (TOCN/PPy) was used as electrically conductive sensitive material. A CPW-based sensor was designed, screen-printed and experimentally tested over 22- 72%RH range. The measured sensitivity was 0.136°/%RH at 5.7 GHz. The insertion losses decreased by 1.15 dB only.