Optical filters are used in many devices, including telescopes, light bars, cameras, laser measuring technology, smartphones and other systems. They ensure that the light is reflected, or transmitted, depending on its wave length.
Researchers from the Karlsruhe Institute of Technology developed new materials, and an innovative process to print such filters on inkjet printers. At Hannover Messe 2023, they demonstrated how to manufacture custom optical filters and mirrors in an energy-efficient and cost-effective manner.
“Optical mirrors and filters are needed wherever light is involved in your work,” Uli Lemmer explains, Professor Uli. “Until now, however, they have been manufactured in complex vacuum systems that consume a lot of energy and material and have a comparatively low throughput.”
These layers are stacked on top of other layers. Usually, these layers are made of two different materials. The layer thickness and refractive index will vary. The material is evaporated in conventional production over a wide area, resulting in material losses. These evaporation technologies require high temperatures. They are therefore energy-intensive.
With their novel process, the research team intends to reduce manufacturing costs and flexibly adapt the product’s properties to the respective application. That’s why the researchers used inkjet printers to create inkjet optical filters (IJPOFs).
They used two inks that were specifically created for this purpose. Drop by drop, the first ink is applied until the desired layer thickness has been reached. The product is then cured using UV light. The second ink is used to make the next layer using the same technique. Inkjets create optical filters using two materials, which are alternately applied.
Researchers report that the inkjet printers’ filters are in high demand in applications such as spectroscopic devices in medicine, metrological equipment for the chemical industry or telescopes that need a large area to reflect light.
The team created dielectric and optical mirrors using the new inkjet printing technology. The filters are ultra-high reflecting at 99%, and have custom optical properties. The method can be used for optical components that are in the micrometer range and are found in cameras. However, it is also suitable for large surfaces like PV modules.
Uli Lemmer’s doctoral researchers and he aim to take this innovative technology, for the production and manufacture of a new-generation of optical filters and reflectors, to commercial success through the founding of a spin off company.