Unclonable fluorescent tags produced on bioplastics by in-situ electron beam irradiation

Counterfeiting of assets, documents, and goods is a growing issue with substantial economic impacts from the proliferation of fake products and significant risks to consumer health and safety. This highlights the urgent need for advanced anti-counterfeiting technologies. In this work, we demonstrate a novel approach to creating unclonable fluorescent tags on poly(lactic acid) (PLA) films using electron beam irradiation. By optimizing irradiation conditions, we successfully control the formation of carbon dots on the surface of the PLA-based film, resulting in the formation of carbon dots that emit fluorescence. The formation of carbon dots was confirmed by Raman spectroscopy and transmission electron microscopy. These carbon dots display tunable emission intensity and spatial distribution, allowing the creation of both deterministic and stochastic fluorescent patterns.

Our findings demonstrate that the resolution and definition of the resulting images can be tailored to create either reproducible patterns or unique, unclonable ones. For the unclonable tags, even when identical imaging and processing conditions are applied, the tags exhibit distinct characteristics, highlighting the stochastic nature of the process. The robustness of this method was validated through fluorescence readings and independent measurements by different operators using varied equipment, ensuring reliable and consistent results. To assess the uniqueness and reliability metrics of physical unclonable functions (PUFs), we evaluated the Hamming distance, obtaining mean values of 43.5 % for uniqueness and 88.7 % for reliability. These results underscore the reliability and reproducibility of the produced tags as PUFs.