Since Perseus escaped the gorgons with his helm of invisibility, the idea of a cap or cloak of invisibility has been a fixture of myth and fairy tale. A helmet of invisibility appears in Norse mythology, and the first mention of an invisibility cloak occurs in Welsh folklore, with the story of Caswallawn (the historical Cassivellaunus), who used one to murder Caradog ap Bran and his fellow chieftains. From then via H. G. Wells’ The Invisible Man through Jack the Giant Killer, via science-fiction to Harry Potter, invisibility has been the stuff of fantasy.
Now scientists at the University of St. Andrews in Scotland maybe about to change all that, as they have created a material which could be used to create an invisibility cloak. The material, called Metaflex, may provide a way to manipulate light to render objects invisible.
Metamaterials have already been developed, which bend and channel light to render objects invisible at longer wavelengths, but visible light poses a greater challenge because its short wavelength means the metamaterial atoms have to be very small. So far such small light-bending atoms have only been produced on flat, hard surfaces unsuitable for use in clothing.
In 2006, a group of US/UK scientists announced they had devised a way of cloaking that made solid objects disappear from sight. At the time, Sir John Pendry, the theoretical physicist at Imperial College London, who developed the idea, said cloaking devices to hide vehicles from radar were only a matter of years away, but as Pendry explained, “Our device is more an invisibility shed than an invisibility cloak.”
Today newspapers report scientists at St Andrews believe they may have overcome this problem, as:
They have produced flexible metamaterial “membranes” using a new technique that frees the meta-atoms from the hard surface they are constructed on. Metaflex can operate at wavelengths of around 620 nanometres, within the visible light region.
Stacking the membranes together could produce a flexible “smart fabric” that may provide the basis of an invisibility cloak, the scientists believe. Other applications could include “superlenses” that are far more efficient than conventional lenses.
Describing their work in the New Journal of Physics, the researchers write: “Arguably, one of the most exciting applications of Metaflex is to fabricate three-dimensional flexible MMs (metamaterials) in the optical range, which can be achieved by stacking several Metaflex membranes on top of one another…
“These results confirm that it is possible to realise MMs on flexible substrates and operating in the visible regime, which we believe are ideal building blocks for future generations of three-dimensional flexible MMs at optical wavelengths.”
Lead scientist Dr Andrea Di Falco said: “Metamaterials give us the ultimate handle on manipulating the behaviour of light.”
The full report from the New Journal of Physics can be read here.