Electrical functionality of inkjet-printed silver nanoparticle conductive tracks on nanostructured paper compared with those on plastic substrates

In this study, we use nanostructured paper made from cellulose nanofibres (CNFs) as a flexible printable material for inkjet-printing of silver nanoparticle (AgNP) ink. The nanostructured paper is prepared by sheet casting of 10-40 nm wide mechanically fibrillated aqueous CNFs in suspension. The resulting nanostructured paper, in the form of densely packed laminar layers, has low surface roughness (40 +/- 2.3 nm) and a nanoporous network structure. This unique surface feature helps the ink vehicles to permeate through the nanopores and also aids absorption along the fibril direction parallel to the surface while retaining the silver nanoparticles on the surface to compete with the initial spreading and final evaporation processes. As a result, well-defined inkjet-printed AgNP conductive tracks (similar to 400 mu m wide) on nanostructured paper show lower electrical resistance (1.57 +/- 0.09 Omega cm(-1)) than those on commonly used plastics, including polyimide (PI, 2.07 +/- 0.17 Omega cm(-1)) and poly(ethylene naphthalate) (PEN, 2.10 +/- 0.16 Omega cm(-1)), at a moderate curing temperature of 150 degrees C for 1 h. The inkjet-printed conductive tracks on nanostructured paper also show better electrical performance during and after folding than those printed on plastic substrates, such as PI, and exhibit stable electrical properties throughout a test period of 1000 h in a moisture resistance test (85 degrees C and 85% relative humidity). The better overall electrical performance compared with that of tracks on plastic substrates highlights the potential of genuinely nanostructured paper as a printing substrate for flexible printed electronics.