Fractal-camouflage clothing is almost a reality
Physicists are a step closer to creating an invisibility cloak, having unveiled a revolutionary new design of electronic material.
Soon we could find ourselves wearing the ultra-thin invisible clothing, which allows the wearer to be completely invisible in a wide range of situations. There have been numerous attempts at creating an invisible material and these have only worked when using specific colours, light and wavelengths.
The different types of design:
Optical camouflage technology is a modified background image, which is projected onto a cloak of retro-reflective material. Anyone standing at the projection source won’t be able to see the wearer.
The “mirage effect” is created by an electric current, which passes through submerged carbon nanotubes – creating very high local temperatures and causing light to bounce off them, hiding the objects behind.
Adaptive heat cloaking is achieved by a camera, which records background temperatures – these are displayed by sheets of hexagonal pixels, which are even able to camouflage moving vehicles from heat-sensitive cameras, by changing the temperature very quickly.
Calcite crystal prism takes place when the Calcite crystals send two polarisations of light into different directions. The prism-shaped crystals are glued together in a specific geometry, polarising the light that can be directed around small objects, effectively cloaking them.
“Our active cloak is a completely new concept and design, aimed at beating the current limits and we show that it indeed does,” explains Prof Andrea Alu.
Recently a new design was submitted to the journal Physical Review Letters, by Prof Andrea Alu, of the University of Texas. He mentions that by actively adapting to the light of the surroundings, his design could create an invisible cloak. The surface of the material is coated by amplifiers, creating an electric current that makes it vanish.
Prof Alu and his team looked at three popular types of “passive” cloaks, which don’t require electricity – a plasmonic cloak, a transformation-optics cloak and a mantle cloak. The problem with the current designs is that they only worked at limited bandwidths and could only hide objects from microwaves. They also noted that at different frequencies the material acted as a beacon, which made the hidden object more obvious. The study concluded that for a passive coat to allow complete invisibility is “impossible”.
Prof Andrea Alu concludes that a far more promising opportunity is “active” cloaking technology, where designs rely on electrical power to make an object “vanish”. These cloaks can be less conspicuous and thinner than the passive designs. The ultra thin cloak hides an object from detection at a frequency range “orders of magnitude broader” than any other available passive cloaking technology.
Cloaking material will be extremely beneficial in biomedical sensing, microscopy, energy harvesting devices and the military. According to Prof David Smith of Duke University, who was one of the team members involved in the creation of the first cloak in 2006, the new design was one of the most detailed he had yet seen.