Researchers at the University of Illinois have developed a new method of printing silver ink that could lead to dramatic decrease in the price of flexible electronics. Previous conductive silver inks used in electronics had to be printed at very high temperatures, mandating that the plastics they were printed on be able to hold up under the heat — which increased the cost of materials. The new ink lowers the energy usage needed during the process and it can be printed at 194 degrees Fahrenheit, so lower-cost, flexible plastics can be used as a base.
The new silver ink was developed by Jennifer Lewis, the Hans Thurnauer Professor of Materials Science and Engineering, and graduate student S. Brett Walker. The team published their research today in the Journal of the American Chemical Society. Their breakthrough solution consists of silver acetate and ammonia. The silver dissolves quickly in the solution — in just minutes — improving on previous solutions which took hours of complicated steps to produce, and remains usable for weeks.
Most conductive silver inks are printed in extremely hot temperatures and take a long time to dry. Lewis and Walker’s solution takes just minutes to dry leaving behind just the silver as the liquid evaporates. The new ink can also be printed more accurately, through a 100-nanometer nozzle — which is much smaller than current techniques — allowing for more exacting results. It can also be used in airbrush spraying on large continuous surfaces.
“For printed electronics applications, you need to be able to store the ink for several months because silver is expensive,” Walker said. “Since silver particles don’t actually form until the ink exits the nozzle and the ammonia evaporates, our ink remains stable for very long periods. For fine-scale nozzle printing, that’s a rarity.” In addition to all of these features the new ink can be printed on cheaper plastics, which are generally more flexible and less expensive than what is currently used, opening up the door to a whole new range of flexible electronics which are currently prohibitively expensive to create.