Due to the pervasive nature of water, water vapor, and moisture, there
is a strong influence on the product quality of a multitude of goods
(e.g., food, chemicals, electronics, ammunition, etc.). Humidity as
environmental water vapor is therefore of strong interest for the
purposes of measurement and control throughout the life cycle of goods
not only in regard to their use but also during manufacture, transport,
and storage. One of the key requirements of monitoring measurement
systems is to determine critical threshold or accumulated dosage
exposure conditions. Nowadays, RFID technology is established, and a
large number of standardized and non-standardized solutions of differing
complexity exist. Sensor-enhanced RFID tags not only provide unique
identification information but also additional sensor information.
Fulfilling a monitoring task on item level is challenging when there is
no continuous supply of electric energy available, a common application
constraint in sensor-enhanced RFID applications. Application constraints
are impeded due to the low cost requirements on the RFID market.
Wireless passive humidity monitoring sensor solutions, in which the
exceedance of a humidity threshold leads to a permanent, preferably
irreversible change of a sensor parameter are proposed in this study. In
the presented solutions, this is either a lasting electric resistance
(IREV-R sensor approach) or an electric capacitance change (IREV-C
sensor approach). For this purpose a number of physico-chemical
phenomena are technically exploited in different sensor arrangements.
These are the deliquescence of salts as threshold detection mechanism,
transport processes in porous media as well as chemical liquid phase
sintering of metal nanoparticles. The sensor principles introduced
effectively act as humidity threshold-activated relative humidity
dosimeters. For use in combination with RFID tags single use, low-cost
sensor solutions are favored. Inkjet print as a representative mass
