Catching A Thief With Nanopillar Security

To protect intellectual property, drugmakers often add holograms or other security tags to a medicine’s packaging. The problem is, counterfeiters are smart: Over time, the criminals figure out how to produce replicas of the tags. Security labels “need to provide a greater degree of protection and be difficult to produce in low-tech environments,” says Nicholas A. Kotov of the University of Michigan. Along with Seok Jae Lee of Korea Advanced Institute of Science & Technology and coworkers, Kotov has now produced and patented an anticounterfeit tag that becomes visible when fogged by a person’s breath (Adv. Mater. 2014, DOI: 10.1002/adma.201401246). To produce the tag, the researchers first pour an optimized mixture of polyurethane and the light-activated adhesive NOA63 into a silicon-based mold dotted with tiny cylindrical holes. The team then uses ultraviolet light to cure the mix, which later peels from the mold easily. The resulting iridescent film has an array of 20-nm-high pillars on its surface that, when subsequently coated with layers of patterned polyelectrolyte, form the security tag. Moisture from a person’s breath beads up on the nanopillars but not on patches of the polyelectrolyte, revealing the hidden image.