It seems that every day we see news about exciting breakthroughs in printable flexible electronic applications ranging from batteries to solar panels to wearable electronic clothing. We may look back upon the discovery of a particle-free, reactive silver ink by researchers at the University of Illinois as a turning point in revolutionizing the manufacturing of a wide range of such electronic products.
Recognizing the amazing value of this breakthrough in conductive silver printing is as simple as comparing the existing process with the new process. Three major benefits stand out:Old: Hours of mixing and several process steps are required to produce solutions of silver micro-particles for the current state-of-the-art silver inks.
New: The newly developed ink, consisting of silver acetate in ammonia solution, can be mixed in minutes.
Old: Microparticles of silver jammed small printing nozzles, limiting how fine a line could be laid down.
New: The transparent, particle-free ink can be sprayed through 100 nanometer nozzles, ten times smaller than existing inks can use.
Old: High annealing temperatures waste energy and require expensive flexible substrates.
New: Annealing this reactive silver ink at 90 degrees Celsius results in conductivity comparable with that of pure silver, opening opportunities for lower energy manufacturing on cheap paper or plastic substrates.
The new ink has other advantages as well. It is a thinner (less viscous) solution, which can be used for inkjet printing, direct ink writing, or airbrush spraying. It reacts and dries quickly for faster processing times. It is stable in storage for long periods; according to the press release: "for fine-scale nozzle printing, that’s a rarity.”
The research was led by Jennifer Lewis, the Hans Thurnauer Professor of Materials Science and Engineering at University of Illinois, Champaign and supported by graduate student S. Brett Walker. Their discovery is published in in a paper, "Reactive Silver Inks for Patterning High-Conductivity Features at Mild Temperatures," in the Journal of the American Chemical Society