Executive Summary :
Objective: Development of a stable, oxidation-resistant, low-temperature sintering copper ink will be a breakthrough in inkjet technology, and has the potential to significantly reduce the cost of printing conductive circuits like PCBs, RFID tags, PC bus cable etc
Summary: The holy grail in printed electronics research is to develop a durable, antioxidant copper based ink, which is not at all available in the market so far. The NIIST team has several years of experience working with screen printable conductive inks, and using this knowledge they wanted to create a niche on cheap conductive inkjettable inks. If such an ink is ever developed, it can replace the costly silver inks that are dominating the printed electronics world. The present project proposes a workable strategy to control the oxidation of copper nanoparticles using quantum dot like nanoparticles of silver and graphite in the form Cu@Ag and Cu@C. Accordingly, copper nanoparticles and silver quantum dot like nanoparticles will be generated using a series of scalable chemical methods. The oxidation of copper will be prevented using Cu@Ag core-shell synthesis through different synthesis procedures. Using the encapsulated copper nanoparticle, conductive ink will be prepared and evaluated. In the alternate strategy, we plan to develop graphite quantum dot like nanoparticles (D< 20 nm) in a hydrothermal way and subsequently to make Cu@C core shell synthesis through suitable chemical methods. We believe that using these strategies, oxidation resistant copper nanoparticles protected by ultra-small nanoparticles of silver and graphite with high electrical conductivity (>104 S/m) could be generated. Using these stable nanoparticles, inkjettable conductive inks will be developed and their physical, chemical and electrical properties including shelf life will be evaluated. The low temperature curable inks are formulated by the addition of suitable solvents, dispersants and binders. The printed Cu ink structures will be subjected to pulsed UV sintering, to improve their electrical conductivity. Subsequently thin film transistors will be realized by inkjetting the newly developed stable copper nanoink as the source, drain and gate, of an organic thin film transistor. If the present strategy of generating high conductivity antioxidant copper ink works, this would be a breakthrough in the research on cost effective conducting inks and cheap flexible devices.