Facile patterning using dry film photo-resists for flexible electronics: Ag nanowire networks and carbon nanotube networks

In this study, we explored the use of a dry film photo-resist (DFR) in the patterning of Ag nanowire and carbon nanotube (CNT) networks for the first time. With a simple lamination process, the DFR was uniformly coated on the Ag nanowire and CNT networks on poly(ethylene terephthalate) (PET) substrates without a post-thermal baking process. Furthermore, a Na2CO3-based developer enabled the networks to be patterned without loss of conductivity. Scanning electron microscopy images revealed that the Ag nanowire and CNT networks were successfully patterned with a pattern width up to similar to 30 mu m. The patterned Ag nanowire networks were confirmed to follow the percolation theory, showing a logarithmically linear increase in resistance as the pattern width decreased. The results indicated that there was no harmful effect on the Ag nanowire network during the patterning process. In addition, the mechanical reliability under bending fatigue was explored, which revealed a pattern-size dependent bending fatigue behavior, where the Ag nanowire networks with smaller pattern widths showed a higher increase in resistance during bending fatigue. This simple patterning method using DFRs combined with the roll-to-roll process is expected to lead the future patterning technology of flexible electronics.