Size-controllable copper nanomaterials were easily obtained via an improved polyol process by regulating the dosage of copper source and reducing agent. The monodisperse copper nanoparticles with strong antioxidation properties were employed as fillers to fabricate conductive ink. The copper-based ink could be screen-printed onto flexible substrates, which shows persistent stability and uniform properties without color change for a few days. After heating at 240 A degrees C (40 min) in N-2 atmosphere, a low electrical resistivity of 16.2 mu Omega cm was obtained for the copper nanomaterial-based conductive pattern.