The ink-jet printing humidity sorption sensor—modelling, design, technology and characterization

Abstract

This paper presents a humidity sorption sensor made with an ink-jet printing technique. Nafion was applied as a humidity sorption material. After the presentation of sensor construction and sensor fabrication technology, a lot of effort has been made for detailed sensor tests and characterization. The sensor model based on a RC transmission line with distributed parameters (Jachowicz and Senturia 1981/1982 Sensors Actuators 2 171–86) has been carefully described and validated by a comparison with the sensor empirical parameters, measured in a broad range of measurement frequencies. On the basis of achieved results, some general conclusions for humidity sorption sensors on both the sensor fabrication technology and the sensor modelling have been made and presented in this paper.

Inkjet and microcontact printing of functional materials on foil for the fabrication of pixel-like capacitive vapor microsensors

“…The time response of the sensor, defined as the interval needed to evolve from 10% to 90% of the step signal, was t r = 5 s. On the other hand, for steps involving higher values of R.H., such as 10-60% R.H., the sensor signal was slightly further away from a pure exponential behavior than for slow R.H., and a time constant of s = 3 s was found; the time response t r was 14.1 s. This scenario suggests that the diffusion coefficient decreases at high values of R.H. In any case, the sensor response is several folds faster than the response of the most part of the previously reported [23,30,31,33] sponds to e r = 3.8, in good agreement with different CAB manufacturers. The device presented a capacitance per surface area and sensitivity per surface area (at 10% R.H. and room temperature) of 48.1 pF mm À2 and 82 fF mm À2 per 1% R.H., respectively, which is around one order of magnitude higher than in previously reported printed capacitive gas sensors [23,30,33].…”

“…Also, recently some research groups have expanded the field of capacitive gas sensors to foil substrate, maintaining the use of standard technology for patterning [28,29]. It has been only over the last 5 years, when some examples of printed (mainly inkjet and gravure) capacitive gas sensors have been reported [9,12,23,[30][31][32][33]. The most part of the aforementioned works were based on interdigitated electrodes (IDE) to facilitate postfabrication coating.…”

Comparative study of printed capacitive sensors

“…The fabrication time is much lower than in the case of other structures because no other sensing layer was needed [7,14,15] and also because these sensors only required printing one layer on one side of the substrate. In a previous work, we demonstrated that the layer thickness does not contribute significantly to capacitance and therefore the definition of electrodes by only one printed layer is enough for a proper sensor performance [13].…”

Printed single-chip UHF passive radio frequency identification tags with sensing capability

“…Different approaches have been followed to include the sensing capability in the capacitor. The most frequent strategy has consisted of depositing a sensing layer over the electrodes capacitor [14][15][16]. Some common polymers are cellulose acetate butyrate (CAB), polymethylmethacrylate (PMMA) and polyvinylchloride (PVC), among others.…”