For several years, researchers have known that carbon nanotubes are one of the blackest known materials. These tiny scaffolds—which have a structure like rolled-up chicken wire—barely scatter light. Indeed, some believe the nanotubes are so black that they might make a new type of camouflage—one that conceals anything as a flat black blob. To test the idea, scientists etched a picture of a tank onto a silicon surface (inset). On its own, the three-dimensional object was clearly visible because light scattered and reflected off the tank's features, as it does with all everyday objects, black or otherwise. However, when the researchers coated the tank with nanotubes, the etching appeared to vanish, as though the surface was perfectly flat. Such camouflage, described in a paper published this week in Applied Physics Letters, wouldn't actually blend an object into its surroundings. But it would turn anything into a spooky silhouette, like a black cut-out.
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