Self‐Assembled Physical Unclonable Function Labels Based on Plasmonic Coupling

Abstract Counterfeiting of goods and pharmaceuticals impacts economies around the globe and threatens human health. Hardware‐based cryptography exploiting physical unclonable functions (PUFs) provides the means to securely identify and authenticate products. While PUFs based on optical response are among the hardest to replicate, they often suffer from low encoding capacity and often complex and expensive read‐out. Here, we report PUF labels with nanoscale features and optical responses that result from the guided self‐assembly of plasmonic nanoparticles. Nanosphere lithography combined with DNA origami placement is used to create tightly packed yet randomized nanoparticle assemblies. Nanoscale variations within these assemblies define the scattering color of the individual spots that are arranged in a hexagonal lattice with spacing down to the optical resolution limit. Due to the nanoscale dimensions, the intrinsic randomness of the particle assemblies and their resulting optical responses, the PUFs are virtually impossible to replicate, while they can be read out with a cost‐effective 3D‐printed microscope.