"What we have done is taken that material and made it much thicker," Valentine says. Some groups managed it with very thin layers, virtually only one atom thick, but these materials were not practical to work with and absorbed a great deal of the light directed at it. This was done using microwaves in 2006 by Professor David Smith of Duke University in North Carolina and Professor Sir John Pendry of Imperial College London. The military, which funded the research, is especially keen to develop materials that could usher in an entire new generation of stealth technology.įor a metamaterial to produce negative refraction, it must have a structural array smaller than the wavelength of the electromagnetic radiation being used. Wells' Invisible Man to the adventures of Harry Potter. The holy grail of metamaterials has become the kind of invisibility shield that has fired the human imagination from H.G. "Instead of the fish appearing to be slightly ahead of where it is in the water, it would actually appear to be above the water's surface," Valentine says. The negative refraction achieved by the teams at Berkeley would be different. These are illusions caused by the light bending when it moves between water and air. Or if you put a stick in the water, the stick seems to bend away from you." "When you see a fish in the water, the fish will appear to be in front of the position it really is. "In naturally occurring material, the index of refraction, a measure of how light bends in a medium, is positive," he says. Valentine's team made a material that affects light near the visible spectrum, in a region used in fibre optics. One approach uses a type of fishnet of metal layers to reverse the direction of light, while another uses tiny silver wires, both at the nanoscale level.īoth are so-called metamaterials, artificially engineered structures that have properties not seen in nature, such as negative refractive index.Įach new material works to reverse light in limited wavelengths, so no one will be using them to hide buildings from satellites, says Jason Valentine, a doctoral student who worked on one of the projects. The experiments, led by Professor Xiang Zhang at the University of California at Berkeley and the Lawrence Berkeley National Laboratory, are reported simultaneously today in the British journal Nature and the US-based journal Science. Scientists have created two new types of materials that can bend light the wrong way, creating the first step toward an invisibility cloaking device.įor now the vanishing act takes place on a nanoscale, measured in billionths of a metre.īut there is no fundamental reason why the same principles cannot be scaled up one day to make invisibility cloaks big enough to hide a person, a tank or even a tanker, the scientists say. Invisibility device possible, in theory.
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