Graffiti-repelling Walls

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Graffiti-repelling Walls

Times Square subway station in 1974 bears witness to what has been a decades-old problem for countless cities.

Erik Calonius/The National Archives

It's unlikely that graffiti artists will appear on the FBI's Ten Most Wanted Fugitives list, but cities and municipalities take this particular kind of vandalism very seriously. Chicago spent $4.1 million in 2012 on its anti-graffiti program and, in 2011, removed 137,459 instances of spray-painted artwork from bridges, buildings and signs [source: Novak]. In Los Angeles, the problem -- and the necessary budget to address it -- is even bigger. That's a lot of money and man power that could be directed to other social services and city programs.

Graffiti-cleaning crews use a variety of techniques to sponge away illicit artwork -- overpainting, chemical removal and power washing. Unfortunately, some of these methods can produce a bigger eyesore than the vandalism itself. Enter the graffiti-repelling wall, which features a nonstick material that either resists paint adhesion or makes removal far easier because the paint doesn't interact with the protected surface. Scientists have fashioned one such material to mimic the leaves of the lotus flower. The surface of these leaves bear an intricate array of microscopic ridges coated in wax. The ridges trap air between them and, as a result, water falling onto the leaf forms individual droplets that simply roll off. A wall or sign coated in such a material -- a nanostructure built in the lab but inspired by nature -- would foil graffiti artists and probably make city mayors very, very happy.

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