Self-assembly of coordination polymers on plasmonic surfaces for computer vision decodable, unclonable and colorful security labels

Abstract

Incorporating security labels with physical unclonable functions (PUFs) into products is considered as the most effective anti-counterfeiting measure. Here we reported a PUF-based security label composed of random colorful patterns. The security label was fabricated through self-assembly of coordination polymers – a cupric bromide complex of pyrazine 1,4-dioxide – on lithographically defined plasmonic surfaces. The coordination polymer exhibits excitation wavelength dependent fluorescence fingerprints, which enables encoding spectral information in the polymer. The fluorescence peaks of each spectrum can be easily converted to a unique anti-counterfeiting barcode. The developed security label also carries 2D graphical information, which can be visualized under bright-field, dark-field and fluorescence multifunctional microscopy. It is multicolored with high contrast under the bright/dark-field modes and single color under fluorescence mode. The multicolors originate from polymer-thickness dependent optical interference. The encryption with colors on a 50 μm square produces a minimum of 3⁷³⁹ PUF codes for the realized authentication system. Moreover, we developed a convenient and reliable authentication strategy based on the computer vision technique to verify the colorful PUF patterns with different definition, rotation angles, brightness, magnification and a mixture of these factors. A high correct validation rate of 100% is achieved using a match threshold of 0.3.