To develop their anti-counterfeiting system, the researchers laser-printed QR codes on paper and then sprayed the PUF pattern on the surface.
The PUF inks contained microparticles, which formed random patterns that showed up as white spots on a black background when magnified. To validate their system, the team generated 10,000 tags and imaged them with a smart phone camera to establish a registry. Then, they re-imaged the tags with different smart phone readers and tried to match them to the registry.
The system correctly identified 76 per cent of the PUF tags. None of the tags were identified incorrectly, but some codes that were dirty or out-of-focus required an additional scan. The researchers estimate that the system can generate 2.5 × 10120 unique codes.
The team comprised Riikka Arppe-Tabbara, Mohammad Tabbara and Thomas Just Sørensen who reported their results in ACS Applied Materials & Interfaces.