Flexible electronic circuits, made in 3D printing
The research team led by Tomke Glier from the University of Hamburg is demonstrating the potential of their process with a flexible capacitor, among other things. “Functionalizing 3D-printable polymers for different applications was the goal of this study,” reports Michael Rübhausen, physics professor at the Center for Free-Electron Laser Science (CFEL), a cooperation between DESY, the University of Hamburg and the Max Planck Society. “With our novel approach, we want to integrate electronics into existing structural units and make components more intelligent in terms of space and weight”.
Rübhausen led the project together with DESY researcher Stephan Roth, a professor at the Royal Institute of Technology in Stockholm. Using the bright X-ray light from DESY’s PETRA III research light source and other measuring methods, the team precisely analyzed the properties of the nanowires in the polymer. At the heart of the technology are silver nanowires, which form a conductive braid. These wires are typically several tens of nanometers thick and 10 to 20 micrometers long. X-ray analysis shows that the structure of the nanowires in the polymer is not changed, but that the conductivity of the braid even improves thanks to compression by the polymer, as the polymer contracts during the curing process.
The silver nanowires are applied to a substrate in suspension and dried. For cost reasons, the aim is to achieve the highest possible conductivity with as few nanowires as possible. This also increases the transparency of the material. In this way, layer by layer, a conductive path or surface can be produced. A flexible polymer is applied to the conductive tracks, on which conductive tracks and contacts can in turn be placed. Depending on the geometry and material used, various electronic components can be printed.
In this paper, the researchers produced a flexible capacitor. “In the laboratory, we carried out the individual work steps in a layering process, but in practice they can later be completely transferred to a 3D printer,” explains Glier. However, the further development of conventional 3D printing technology, which is usually optimized for individual printing inks, is also essential for this. In inkjet-based processes, the print nozzles could clog up due to the nanostructures.
In the next step, the researchers want to test how the structure of the nanowire conductor paths changes under mechanical stress. “How well does the wire mesh hold together during bending? How stable does the polymer remain,” said Roth, referring to typical questions. “X-ray investigation is very suitable for this because it enables us to look into the material and thus analyze the conductive paths and surfaces of the nanowires.
Researchers from the University of Hamburg, the Royal Institute of Technology in Stockholm, the Wallenberg Centre for Wood Science in Stockholm, the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg and DESY were involved in the work.
Original publication: Functional Printing of Conductive Silver-Nanowire Photopolymer Composites; Tomke E. Glier et al, “Scientific Reports”, 2019; DOI: 10.1038/s41598-019-42841-3
More information: https://www.desy.de/news/news_search/index_eng.html?openDirectAnchor=1623&two_columns=1
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