One of the prevalent concerns about the proliferation of industrial 3D printing has to do with counterfeit parts and IP protection, with manufacturers wondering what the most effective tools are to keep their parts secure. It is interesting then to learn that researchers from the Singapore University of Technology and Design (SUTD) have turned to additive manufacturing to help solve counterfeiting problems in other industries.
Specifically, the SUTD researchers have developed a new type of anti-counterfeiting device called “holographic colour prints” that use nano 3D printed polymer structures to identify the validity of important documents such as ID cards, passports and banknotes. The team, led by associate professor Joel Yang, recently described the 3D printed optical device in a research paper published in the journal Nature Communications.
Made up of tiny 3D printed polymer structures, the holographic colour prints look like standard, 2D colour prints when seen in white light. When the print is lit up with a laser pointer, however, the optical device projects up to three different images onto a screen—compared to more traditional diffractive optical devices which project single images.
The enhanced security capability of the 3D printed optical device could make it harder for counterfeiters to reproduce important documents, something which is becoming increasingly complex as counterfeit production techniques become more sophisticated. Presently, many of the most popular anti-counterfeiting products, found in electronic device packaging, medicine bottles and bank cards, are based on holograms. These devices, however, only modulate the phase light they are exposed to and can be reproduced with relative ease.
Holographic colour printing, for its part, modulates both the phase and the amplitude of light, making it more complex. This, the researchers explain, was achieved by creating a new type of nanostructured pixel arrangement on a planar surface. Each printed pixel functions as a sort of speed bump and road block for light, which results in phase control and amplitude, respectively.
“The relationship of holograms in combating counterfeiting is analogous to antibiotics against infections,” explained associate professor Yang. “Every so often, new technology is needed to deter counterfeiters as the old fashioned holograms become easier to copy.”
Notably, the researchers developed an algorithm that automatically determines the positions of different phase and coloured filter elements based on multiple images input into it. The device is then produced using a nanoscale 3D printer and uses varying thicknesses of polymerized cuboid to modulate the phase plates to form three multiplexed holograms.
“For the first time, multiple holograms that are colour selective are ‘woven’ into a colourful image using advanced nanofabrication techniques,” Yang added. “We are hopeful that these new holographic colour prints are user friendly but counterfeiter unfriendly: They are readily verified but challenging to copy, and can provide enhanced security in anti-counterfeiting applications.”