A printed capacitive–resistive double sensor for toluene and moisture sensing

This paper presents a flexible printed sensor to detect two different magnitudes: toluene content and relative humidity. This device has been manufactured by using two printing techniques: inkjet printing to define the electrodes and screen printing to deposit the sensitive material. The combination in the same area of two different sensors enables the monitoring of two different gaseous chemicals without interference between them. On one hand, moisture content is associated with changes in the electrical permittivity of the chosen substrate (capacitive effect). On the other hand, toluene concentration is measured through variations in volume of the developed composite (resistive effect). Changes to relative humidity and toluene content have been measured in both capacitive and resistive parts as well as their responses to temperature variations.