On inkjet-printed flexible capacitive micro gas sensors: towards digital fabrication

This work presents the evolution of inkjet-printed capacitive micro gas sensors through the development of three different consecutive generations, moving on from planar interdigitated electrodes (IDE) to parallel plates structures. The sensors are composed of silver nanoparticles-based electrodes and a polymeric sensing layer, fully inkjet-printed on flexible polymeric substrates. The focus of this review is put on overcoming the typical resolution limitations of inkjet-printing in order to reduce the sensors size and maximize their nominal capacitance value per surface area. The feasibility of the technology has been already demonstrated for relative humidity (R.H.) detection. This work also highlights the potential of a 4th on-going generation based on single-drop parallel plates devices.