Inkjet printed carbon nanotube networks: The influence of drop spacing and drying on electrical properties

We have measured the electrical resistance of inkjet printed multiwall carbon nanotube networks and found that it depends strongly on the temperature of the substrate during the printing process, with both the resistance and its anisotropy decreasing as temperature increases. A parallel investigation of the surface morphology of the printed networks found long raised ridges running parallel to the printing direction, with the height of the ridges decreasing with increasing substrate temperature. Both these observations are shown to be associated with segregation of the nanotubes during drying (coffee staining) and that this segregation is suppressed at higher substrate temperatures, with the lowest resistance values and anisotropy found with a substrate temperature of 70°C. Network conductance was found to increase with increasing layer thickness and similar results are obtained through a reduction in drop spacing or by printing multiple layers. © 2012 IOP Publishing Ltd.