Researchers at the ETH Zurich University of Technology have developed a method for printing electrodes using a nanoprinting technique. The printed grid of gold or silver nanostructures is virtually invisible to the naked eye.
According to the researchers, the electrodes made of gold nanoparticles conduct themselves much better and are more transparent than films of indium-tin-oxide, which make most touchscreens conductive today. Gold and silver, on the other hand, have the disadvantage that they are not transparent in film form. A grid of electrodes can offer a solution, as long as it conducts well enough. The researchers obtained the latter by making the electrodes two to four times as high as they are wide. This ratio ensures that the ‘walls’ conduct electricity well in different directions.
The grid of gold nanowalls is only 300 nanometers thick and is printed on glass through a process called ‘nanodrip’. Nanodrip is technically similar to an inkjet printer and builds up a grid of nanowalls layer by layer. The ink itself consists of gold nanoparticles in a solvent. The solvent evaporates quickly after printing on the substrate.
The nanodrip printing process works with an ‘electrohydrodynamic inkjet printer’. In this process, an electric field pulls a tiny drop of metallic ink, or metal nanoparticles in a solvent, from a glass capillary tube. Due to the combination of the electromagnetic field and the composition of the droplets, the drops that come out of the tube are about ten times smaller than the opening where they emerge, so that very small structures can be printed.
According to the researchers, the next challenge is scaling up the process. The research paper can be found in the journal Advanced Functional Materials.
Grid of printed gold nanowalls of 300 nanometers thick. Photo: Schneider J et al.