All additive inkjet printed humidity sensors on plastic substrate

Functional humidity sensors have been fabricated on polymeric foil PET using all additive processes. The fabrication included inkjet printing and electrodeposition of interdigitated structures followed by the inkjet printing of a test humidity sensing layer. Quantitative and qualitative analysis of the sensor operation led to the understanding and subsequent improvement of the sensor performances by means of the differential measurements method. To the best of our knowledge, it is the first time that electrodeposition of a thicker metallic layer on inkjet printed patterns has shown advantages in the stability and sensitivity of a capacitive humidity sensor. The process exposed in this paper is proposed as a perfect candidate for the fabrication of sensors arrays or disposable sensing platforms where low-cost, light weight and mechanical flexibility are important issues.