Inkjet printing of silver nanowires on flexible surfaces and methodologies to improve the conductivity and stability...

Silver nanowires (AgNWs) are known to be used for printing on rigid as well as flexible surfaces. Here we have developed a systematic approach for using AgNWs synthesized by the polyol method for printing on flexible surfaces using a simple inkjet printing method. Optimized ink formulation used in this work comprises a mixture of Ag NWs suspended in ethylene glycol directly taken after synthesis and isopropyl alcohol. Using such formulation saves time and loss of material while transferring to other solvents, which is the usual practice. The printed patterns demonstrate high conductivity and stability over many months, which can revolutionize the applications of functional nanomaterials in low-cost printed electronics. The importance of fragmentation of nanowires only to achieve specific aspect ratios, to facilitate easy jetting and to prevent clogging is demonstrated. Varied concentrations (10 mg mL^-1 to 50 mg mL^-1) of Ag NWs are used in ink formulations in order to print highly conductive patterns (resistance < 50 Ω sq^-1) in a minimal number of passes. The same composition was also seen to facilitate simple and time-efficient nano-welding at room temperature, which improves the conductivity and stability of the printed patterns.