INM has developed a technique, which allows such conductor paths even on flexible foils as well as on stretchable silicone. INM will be presenting the so called photochemical metallization.
For the proper functioning of touchscreens in smart phones or tablets, microscopically fine conductor paths are required on their surfaces. At the edges of the appliances, these microscopic circuit paths come together to form larger connective pads. Until now, these different conductive paths had to be manufactured in several steps in time-consuming processes. With the photochemical metallization this is now possible in one single step on flexible substrates. The one-step process offers, has several benefits: It is fast, flexible, variable in size, inexpensive and environmentally friendly.
For the new process, the foils are coated with a photoactive layer of metal oxide nanoparticles. After that a colorless, UV-stable silver compound is applied. By irradiation of this sequence of layers, the silver compound disintegrates on the photoactive layer and the silver ions are reduced to form metallic, electrically conductive silver. In this way, paths of varying sizes down to the smallest size of a thousandth of a millimeter can be achieved.
This basic principle allows conductive paths to be created very individually. Writing conductive paths using UV lasers is the process which is particularly suitable for the initial customized prototype manufacture and testing a new design of the conductive path.
The researchers are currently working on a further method, the usage of transparent stamps. These stamps push out the silver compound mechanically; conductive paths then only occur where there is still silver compound. Since the stamps are made of a soft plastic, they can be arranged on a roll. Thus, the initial steps for a roll-to-roll process would already have been taken. It would therefore be possible to manufacture conductive path structures of various sizes on foils on a large sca