KIT researchers have developed innovative fluorescent 3D microstructures to help mitigate forgeries and product piracy.
Though bank notes, documents, and branded products all come with advanced security features, they haven’t been free from counterfeiting. According to the German Engineering Association, the damage caused in 2016 in its branch alone amounted to $8.5 billion.
The proposed 3D microstructure technology is an outcome of a partnership between KIT and the ZEISS company.
“Today, optical security features, such as holograms, are frequently based on two-dimensional microstructures,” says Professor Martin Wegener from KIT’s Institute of Nanotechnology. “By using 3D-printed fluorescent microstructures, counterfeit protection can be increased.”
The new security features have a side length of about 100 µm and are barely visible with the eye or a conventional microscope.
The microstructures consist of a 3D cross-grid scaffold and dots that fluoresce in different colors and can be arranged variably in three dimensions within this grid.
The team used a rapid and precise laser lithography device developed and commercialized by KIT spinoff Nanoscribe, to produce and print the microstructures. It enables highly precise manufacture of voluminous structures of a few millimeters edge length or of microstructured surfaces of several cm² in dimension.
The special 3D printer produces the structures layer by layer from non-fluorescent and two fluorescent photoresists. A laser beam very precisely passes certain points of the liquid photoresist. The material is exposed and hardened at the focus point of the laser beam. The resulting filigree structure is then embedded in a transparent polymer in order to protect it against damage.
According to the researchers, the new process can be extended easily and is extremely versatile. The 3D features may be applied as an embedded foil in security tags to protect pharmaceuticals, car spare parts, or mobile accumulators against counterfeiting.
They could also be integrated into the transparent windows of bank notes.
Image credits and content: Karlsruhe Institute of Technology (KIT)