Electrically conductive materials are needed in numerous applications in microelectronics, nanorobotics, sensor technology or battery technology. Metals would be an ideal solution for this, but while 3D printing of plastics has already advanced into the nanometer range, the production of tiny metal parts has so far proved difficult.
Researchers at the University of Oldenburg are now experimenting with a technique that uses very small nozzles to print tiny, three-dimensional structures out of metal.
"We are trying to push the technological limits of 3D printing. We want to assemble objects atom by atom," explains Dr. Dmitry Momotenko, head of the research group at the Institute of Chemistry at Oldenburg University.
3D printer based on electroplating process
The researchers built and programmed their own 3D printer based on the electroplating process. Electrochemical deposition of metallic precipitates is something that electrochemists can control very well, Momotenko explains. Metal ions are brought into contact with a negatively charged electrode in a salt solution. There, the positively charged particles combine with electrons to form neutral metal atoms and deposit as a solid layer on the electrode. It is the same process that is used, for example, in the chromium plating of car parts.
Currently, the researchers can print pillars, as well as spirals, rings or overhanging structures on the nanoscale. Their process works with copper, silver, nickel, and nickel-manganese and nickel-cobalt alloys. The goal, however, is to develop new types of batteries whose anode and cathode are intertwined at the nanoscale. These could then be charged thousands of times as fast as current models - charging an electric car would be accomplished within seconds.
As early as 2021, Momotenko and an international team succeeded in producing copper pillars with a diameter of 25 nanometers is supported by the European Research Council (ERC). In February 2021, he received a so-called "Starting Grant" for his NANO-3D-LION project, in which he is advancing research on new electrodes in Oldenburg.
His four-member research group faces major challenges. On the one hand, they have to find out how tiny impurities in the protective atmosphere, which are created during the printing process, affect the printed structures. For another, they need to find ways to dissipate the heat that is generated in seconds during battery charging and make the printing technology usable for large batteries. The problem of energy storage is very complex, and of course his team can only contribute a small part, the researcher emphasizes. But he sees himself and his group in a good starting position: electrochemical 3D printing of metals currently offers the only way to realize nanostructured electrodes and test the concept.