While “cloaking” technology may have once been limited exclusively to the realm of science fiction, regular Gizmag readers will know that it is now finding its way into real life – just within the past few years, scientists have demonstrated various experimental cloaking systems that prevent small objects from being seen
, and in one case, from being heard
. Such invisibility systems involve the use of metamaterials
, which are man-made materials that exhibit optical qualities not found in nature. These are able to effectively bend light around an object, instead of allowing it to strike the object directly. Now, mathematicians from the University of Manchester are proposing technology based on the same principles, that would allow buildings to become “invisible” to earthquakes.
We’ve previously seen – or should that be “not seen” – invisibility
cloaks in the laboratory that are able to render two-dimensional objects
invisible to microwaves. Such feats relies on the use of metamaterials
– man-made materials that exhibit optical properties not found in nature and have the ability to guide light around an object. Now researchers at the University of Texas at Austin (UT) claim to have brought invisibility cloaks that operate at visible light frequencies one step closer by cloaking a three-dimensional object standing in free space with the use of plasmonic metamaterials.
Many of the current experimental "invisibility cloaks
" are based around the same idea - light coming from behind an object is curved around it and then continues on forward to a viewer. That person is in turn only able to see what's behind the object, and not the object itself. Scientists from Germany's Karlsruhe Institute of Technology have applied that same principle to sound waves, and created what could perhaps be described as a "silence cloak."
Although Klingon-style disappearing spaceships may not be in our neighborhood any time soon, the technology that could allow
a spaceship to vanish from sight may be here now. Scientists from the University of Michigan have successfully made a three-dimensional etched silicon image of a tank appear as a featureless black void, that completely blended in with the backdrop surrounding it. The secret: good ol’ carbon nanotubes.
You have no doubt seen mirages on the distant surfaces of hot highways before, looking like pools of water shimmering on the asphalt. Such illusions are caused by hot air above the road, which refracts light waves coming down into it from the cooler air above – in other words, the supposed “water” is actually the sky, its image being bent toward you by the low-lying hot air. Well, scientists at the University of Texas at Dallas have put the same principle to work in the lab, and created an invisibility cloak that can be easily switched on and off.
Infrared imaging is used for a range of military applications - such as target acquisition, night vision, homing and tracking - which means that any vehicle with some kind of infrared “invisibility cloak” would hold significant advantages on the battlefield. BAE Systems has tested just such a technology that not only allows vehicles to blend into their surroundings, but can also let it mimic other vehicles or natural objects.
The weird properties of artificially engineered metamaterials
are at the core of research into invisibility cloaking, but engineers from Duke University in North Carolina suggest that these materials could also provide a boost to another of technology's quests - wireless power transmission. In this latest hard-to-get-your-head-around metamaterial scenario, it's not the cloaked object that "disappears" - it's the space between
the charger and the chargee.
Efforts to create a working "invisibility cloak
" have generally involved the use of artificial materials with a negative refractive index known as metamaterials
. Another promising technique
involves the use of a natural crystal called calcite that boasts an optical property known as birefringence, or double-refraction. While both methods have proven successful in rendering very small objects invisible in specific wavelengths of light by bending and channeling light around them, both techniques require the "cloak" to be orders of magnitude larger than the object being concealed. Researchers are now reporting progress in overcoming this size limitation using a technology known as a "carpet cloak."
The quest to build a working “invisibility cloak” generally focuses on the use of metamaterials
– artificially engineered materials with a negative refractive index that have already been used to render microscopic objects invisible in specific wavelengths of light. Now, using naturally occurring crystals rather than metamaterials, two research teams working independently have demonstrated technology that can cloak larger objects in the broad range of wavelengths visible to the human eye.
Take some light bending metamaterials
, incorporate them into flexible fabric
and you have yourself an invisibility cloak. That's the theory anyway, and it doesn't stop at hiding objects. Building on the optical invisibility research
of Professor Sir John Pendry, researchers from Imperial College, London, have now proposed that similar metamaterials could be used to conceal entire events
– get ready for the "Spacetime cloak".