Inkjet printing of chemiresistive sensors based on polymer and carbon nanotube networks

We report about the manufacturing of sensor devices for detection of volatile organic compounds (VOCs) in the air. The sensor comprises three fully inkjet-printed layers of (i) silver interdigitated electrodes (SIDE), (ii) multi-walled carbon nanotubes (MWCNTs) and (iii) poly (styrene-co-maleic acid) partial isobutyl/methyl mixed ester (PSE). We have found that inkjet printing of MWCNT layers and a PSE layer on top yields an interfacial layer leading to the formation of a MWCNTs/PSE composite-like structure. The printed layers act as chemiresistive vapor sensors due to the change of electrical resistance in presence of selected VOCs. The sensor responses to various VOCs were studied by varying the concentration of the chemicals in the air between 50 and 500 ppm. The sensing mechanism can be understood as a fractional volume change of the inkjet-printed polymer that occurs during exposure to VOCs, resulting in a structural alteration of the MWCNT-polymer network. We have found that the sensor response can be defined as a function of the VOC's concentration. To investigate the morphologies of the inkjet-printed thin films, profilometry and scanning electron microscopy (SEM) were employed.