Direct printing of a multi-layer sensor on PET substrate for CO 2 detection

The use of inexpensive gas sensors is a real need for many applications requiring the use of disposable sensors. This work deals with the realization and characterization of a low cost CO2 sensor realized by rapid prototyping techniques. In particular, the sensor consists of a set of InterDigiTed electrodes, over which a double sensing layer made of PEDOT/PSS (CLEVIOS PHCV4, by H.C.Starck) and a solution of pristine graphene powder has been deposited. A silver nano-particle solution is used for inkjet printing the electrodes onto the PET (PolyEthylene Terephthalate) substrate, through a commercial inkjet printer. The sensing strategy is based on the variation of the electrical conductance of graphene due to gas molecules adsorption. The device responsivity observed in two different operating conditions (50 degrees C and 60 degrees C), is 4.0 mu//ppm and 4.7 mu//ppm. The corresponding values of the resolution are 400 ppm and 420 ppm. Main advantages of the developed sensor consist in the cost-effective fabrication techniques and the device flexibility, which are strategic for applications requiring disposable and shapeable devices to be installed into irregular surfaces.