Web‐Like Silver Nanowire Networks via Marangoni‐Induced Self‐Assembly for Physically Unclonable Tags

A silver (Ag) nanoweb‐based physically unclonable tag (PUT) is developed using a photolithography process to enhance security and authentication applications. The Ag nanoweb structure is fabricated via Marangoni‐driven self‐assembly, where solvent evaporation induces surface tension gradients, leading to the random yet process‐consistent patterning of Ag nanowires (Ag NWs) on a substrate. The ink formulation, comprising a binary solvent system, controls the evaporation rate and the resulting nanoweb morphology. The PUTs are patterned using a metal mask and characterized through darkfield microscopy, which enhances the visibility of the Ag NW bundles and allows for efficient binary key extraction. Variations in solvent composition and coating temperature influence the bundling behavior of Ag NWs, affecting surface roughness and optical properties. The optimized conditions yield highly transparent, uniquely structured PUTs that exhibit strong resistance to counterfeiting due to their inherent randomness. The extracted binary keys show performance metrics close to the ideal values, with an encoding capacity of 2976.48, corresponding to 95.37% of the theoretical maximum. The findings provide insights into the role of Marangoni flow in controlling the assembly of nanomaterials and highlight the potential of Ag nanoweb‐based PUTs in scalable and secure authentication applications.