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Open AccessArticle

Wireless Chipless System for Humidity Sensing

Institute for Nanoelectronics, Technical University of Munich, 80333 München, Germany
Faculty of Science, Free University of Bolzen-Bolzano, 39100 Bolzano, Italy
Author to whom correspondence should be addressed.
Sensors 2018, 18(7), 2275;
Received: 16 May 2018 / Revised: 9 July 2018 / Accepted: 11 July 2018 / Published: 13 July 2018
(This article belongs to the Section Chemical Sensors)
This work describes a fully wireless sensory system where a chipless strategy is followed in the sensor part. Alternatively, to characterize only the sensing element, we present the response of the reader antenna when the sensing element is placed in its vicinity: changes in the parameter of interest are seen by the reader through inductive coupling, varying its frequency response. The sensing part consists of a LC circuit manufactured by printing techniques on a flexible substrate, whose electrical permittivity shows dependence with the moisture content. The measurement distance show significant differences in the frequency response: a change of 700 kHz is observed when the measurement is performed directly on the wireless chipless sensor between 20% and 80%RH, while this variation in frequency is reduced more than three times when measuring at the reader antenna with 5 mm distance between elements. Furthermore, we demonstrate the importance of the separation between reader and sensor to get a reliable measuring system. View Full-Text
Keywords: flexible substrate; inductive coupling; inkjet printing; printed electronics; reader; resonance frequency flexible substrate; inductive coupling; inkjet printing; printed electronics; reader; resonance frequency
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Salmerón, J.F.; Albrecht, A.; Kaffah, S.; Becherer, M.; Lugli, P.; Rivadeneyra, A. Wireless Chipless System for Humidity Sensing. Sensors 2018, 18, 2275.

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