Temporal Vs Stable Plasmonic Anticounterfeit Tags for Structural Health Monitoring Studies

Proliferation of counterfeit goods has resulted in exorbitant economic fallout, device reliability issues, and health and safety concerns. Hence, developing anticounterfeit platforms has become imperative for reliable and cost-effective authentication, tracking of products, and detection of potential tamper activity. Here, we report covert anticounterfeit platforms where plasmonic nanoparticles (NPs) were used to develop tags to authenticate goods. The two platforms developed are Unique images and Physical Unclonable Functions (PUFs). Fabrication of Unique images entails assembling plasmonic nanoparticles in arrays with the help of templates, whereas PUFs result from light scattering from randomly drop casted NPs. These techniques allow critical goods to be facilely tagged, and the resultant pattern from either a nanoparticle assembly or individual NPs is analyzed with darkfield optical microscopy imaging. Au and Ag NPs were prioritized due to their tailorable optical responses in the visible spectrum. The sensitivity of metal nanoparticles (particularly Ag) to the environment was also leveraged as a monitor of structural health and to show evidence of tampering. Functionalized Ag NP inks were used to create tags that serve as temporal sensors where changes in color response were tracked with variable exposure times to ambient environmental conditions. These temporal sensors are authenticated with machine learning protocols that keep track of the optical changes with time.