Fabrication of paper-based conductive patterns for flexible electronics by direct-writing

A kind of conductive pen was designed, prepared with nano-silver colloid as the conductive ink and gel-ink pen as the writing implement, and used to draw conductive patterns on paper substrate by direct-writing for flexible electronics. Silver nanoink (20 wt%) was characterized using field emission transmission electron microscopy (FETEM), size distribution analyser (SDA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and selected-area electron diffraction (SAED). Paper-based conductive patterns were investigated by a surface profilometer, a 4-point probe, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. It can be found that silver nanoparticles have a small size, about 2.1 +/- 0.5 nm in diameter with monodispersity, and the melting point sharply decreased to 105 degrees C. A conductive line drawn on weighing paper not only had good mechanical/electrical fatigue properties, but also low resistivity. Especially, when the sintering condition is 200 degrees C for 60 min, the resistivity can be down to 6.8 mu Omega cm, 4.25 times the bulk resistivity. In addition, the reparation of conductive patterns and application in a practical circuit were also studied.