James bond may have to up his game. Cloaking materials can now hide tiny microphones placed on a wall - and they will do the job at all visible wavelengths. Optical cloaks can hide a free-floating object by bending light all the way around it, but only at specific wavelengths. They are usually made of synthetic metamaterials, which have a structure on a scale smaller than the wavelength of light they are meant to deflect.
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