It isn't just bank notes and sensitive documents that need security features to prevent forgery - there are numerous products that need the same protection. Ultimately, losses brought about by product and brand piracy can threaten the very existence of a business. However, current protective measures are often inadequate. The German Mechanical Engineering Industry Association (VDMA) estimates that for 2016 alone, losses in the sector will amount to 7.3 billion euros. This staggering figure shows that the pressure needs to be piled on in the fight against product pirates. One approach is to develop new technologies - and that's exactly what researchers at KIT and Zeiss are doing, with their 3D printed microstructures.
"Current optical security features such as holograms are often based on two-dimensional microstructures," explains Professor Martin Wegener. However, the experts in 3D printing microstructures at the KIT Institute of Nanotechnology recommend a more modern alternative. "Using 3D-printed fluorescent microstructures can provide better protection against counterfeiting." Measuring only around 100 micrometers in length along the side, the new security features are almost invisible to the naked eye - and even when using a conventional microscope. Wegener and his team have developed an innovative process for manufacturing and using the new security features that covers everything from the formation of the microstructures all the way through to reading out the information. The microstructures comprise a 3D supporting grid and dots that fluoresce in different colors and can be arranged in various ways in all three dimensions within this grid. A rapid and accurate laser lithography device from Nanoscribe (a spin-off from KIT) is used to form and print the microstructures. The special 3D printer builds up the structures layer by layer from one non-fluorescent and two fluorescent photographic coatings. A laser beam travels through very precise points in the liquid photographic coating, only curing the material at its point of focus. The delicate structure thus formed is then embedded into a transparent polymer to protect it from damage.
"Security features produced in this way are not just custom formed, they are also complex to produce. All that makes life very difficult for forgers," points out Frederik Mayer from the KIT Institute of Nanotechnology. The new process is also designed to be extendible and suitable for use in a whole range of applications. For example, the 3D features could be integrated into the transparent "windows" of bank notes or used as an embedded film in security labels for protecting pharmaceuticals, spare auto parts and cellphone batteries from counterfeiting. Special readers that can identify fluorescent 3D structures could then be used to check the authenticity of products.
Karlsruher Institut für Technologie (D-76131 Karlsruhe)