Purdue University engineers, following mathematical guidelines devised in 2006 by physicists in the United Kingdom, have created a theoretical design, to make something invisible to one visible light frequency, that uses an array of tiny needles radiating outward from a central spoke.
Creating the tiny needles would require the same sort of equipment already used to fabricate nanotech devices. The needles in the theoretical design are about as wide as 10 nanometers, or billionths of a meter, and as long as hundreds of nanometers. They would be arranged in layers emanating from a central spoke in a cylindrical shape. A single nanometer is roughly the size of 20 hydrogen atoms strung together.
These two images (Cloak off, top. Cloak on, bottom) were taken from corresponding videos depicting scientific simulations performed at Purdue to show how objects might be "cloaked" to render them invisible. The new findings demonstrate how to cloak objects for any single wavelength, not for the entire frequency range of the visible spectrum. But the research represent a step toward creating an optical cloaking device that might work one day for all wavelengths of visible light. The videos show how light interacts with an uncloaked and cloaked object. When uncloaked, as depicted in the first image, light waves strike the object and bounce backward. As depicted in the second image, a cloaking device designed using nanotechnology guides light around anything placed inside this cloak. Credit: Birck Nanotechnology Center, Purdue University
Leonhardt says in his commentary that creating a cloak for rendering total invisibility in the entire visible spectrum would require "further advances in optical metamaterials, new combinations of nanotechnology with highly abstract ideas ..."