Movie theaters, restaurants and other establishments that don't want their clientele to use cellphones may soon have a new weapon: a nanotechnology-derived paint that can block cellphone signals. The paint, from a company called Natural Nano, uses copper particles, combined with a hardware blocking device, to block cellphone transmissions, while allowing other frequencies, including those used for emergency broadcasts, to get through. That distinction may allow the paint system to be sold legally in the US, though that means we'll just have to carry a small vial of paint stripper with us every time we go out to the movies.

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