3D printing – aka additive manufacturing - has established itself in recent years as a promising new manufacturing process for a wide range of components. Chemist Dr Dmitry Momotenko from the University of Oldenburg (Germany) has now succeeded in creating extremely small metal objects using a new 3D printing technique. Possible applications could be in microelectronics, sensor technology or battery technology, Momotenko reports together with a team of researchers from ETH Zurich (Switzerland) and Nanyang Technological University in Singapore in the journal Nano Letters. The team developed an electrochemical process that can be used to produce objects made of copper with a diameter of 25 nanometres.
The printing method is based on the well-known process of electroplating. This process, in which a solid metal is produced from a liquid salt solution, can be controlled very well. For the nanoprinting process of the Oldenburg scientists, a solution with positively charged copper ions is used, which are located in a tiny pipette. The liquid emerges at the end of the pipette drop by drop through a pressure nozzle. In the team's experiments, this orifice had a diameter between 253 and 1.6 nm. Only two copper ions fit through such a tiny hole at a time.
The biggest challenge for the research team was that the growing metal layer could block the opening of the pressure nozzle very quickly. The group therefore developed a technique to monitor the progress of the pressure. Towards this end, they monitored the electrical current between the negative electrode and a positive electrode inside the pipette and automatically adjusted the movement of the nozzle accordingly: The nozzle only approached the electrode for a short time and retracted as soon as the metal layer had exceeded a certain thickness. In this way, the researchers gradually applied new copper layers to the electrode surface. By precisely positioning the nozzle, they succeeded in printing