Metamaterials, which are used to produce the items that are termed "invisibility cloaks," have occasionally been targets of skepticism because they don't actually work in visible wavelengths. A paper published in Nature this week describes the structure of a new metamaterial with a negative refractive index that can misdirect light in most of the visible spectrum, up through blue light, bringing the cloaks a step closer to imparting actual invisibility.
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