Fluorescent 3D printed microstructures could foil the forgers

(Credit: Frederik Mayer/KIT)

The technology, developed by researchers at Karlsruhe Institute of Technology (KIT) and optical manufacturing specialist ZEISS, uses a 3D cross-grid scaffold and dots that fluoresce in different colours and can be arranged variably in three dimensions within this grid. With a side length of about 100 μm, the new security features are barely visible to the human eye or even a conventional microscope. The work is published in Advanced Materials Technologies. 

"Today, optical security features, such as holograms, are frequently based on two-dimensional microstructures," said Martin Wegener, a Professor specialising in 3D printing of microstructures at the Institute of Nanotechnology of KIT. "By using 3D-printed fluorescent microstructures, counterfeit protection can be increased."

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To produce the microstructures, the team used a rapid and precise laser lithography device developed and commercialised by Nanoscribe, a spinoff of KIT. According to the researchers, it enables highly precise manufacture of voluminous structures of a few millimetres edge length or of microstructured surfaces of several cm² in dimension. The 3D printer produces the structures layer by layer from non-fluorescent and two fluorescent photoresists. A laser then very precisely passes certain points of the liquid photoresist, and the material is exposed and hardened at the point of the beam.