Harry Potter-style invisibility cloak is a step closer to reality: 3D printed device that bends light could make objects disappear
- Current invisibility cloaks often tend to draw more attention to object
- This is because waves decay as they pass through artificial material
- New technique uses battery-powered tunnel diodes to boost the power
- Technique works on 3D artificial materials rather than just plain sheets
- 'An invisibility cloak will be a reality in my lifetime,' said Professor Xin
Scientists have been attempting to create invisibility cloaks long before Harry Potter made it popular.
But, because of the way they bend light, current designs have always tended to draw more attention to the object than they deflect.
Now, a US researcher claims to have overcome this problem by integrating battery-powered devices into his design - and he claims an invisibility cloak will be created in his lifetime.
The quest for a true invisibility cloak, seen in films such as Harry Potter (scene pictured), is the holy grail for physicists. But, because of the way they bend light, current designs have always tended to draw more attention to the object than they deflect
Hao Xin, a professor of electrical and computer engineering at the University of Arizona the technology could soon be used to conceal military airplanes and even people.
His US Air Force-funded research is based on the use of porous plastic bowling balls and tiny copper wire circuit boards.
These objects are put together in precise geometrical patterns to bend waves of energy in unnatural ways.
In particular, they reveal a property called 'negative refraction', meaning they can bend a wave backwards.
Metamaterials are synthetic materials engineered to have properties that have not yet been found in nature
Through a prism with negative refraction, a straw leaning in a glass of water would appear inverted.
THE INVISIBILITY CLOAK FOR TIME
The quest for a true invisibility cloak, seen in films such as Harry Potter, is the holy grail for physicists.
But while many have claimed to be able able to briefly conceal objects from view, and even shield sounds, one team has developed a way to cloak entire events.
The say they managed to do this by concealing these events behind strands of laser light.
The technique, called ‘temporal cloaking’ was developed at the Purdue University in West Lafayette using lasers and fibre optics.
The researchers separated strands of frequencies in laser light before changing their respective height.
They then sent this light through a fibre optic cable. By slowing the speed of photons on a particular strand, the intensity of the light was dropped to zero.
This made that particular strand appear invisible, hidden behind or between other strands.
Using this method, the light travelling in front of this strand was sped up, while the trailing part was slowed down to create a gap.
The physicists then used this gap to insert hidden messages in data.
During test, the hidden messages travelled along with the other frequencies, but arrived at the other end marginally out of sync with the photons surrounding it.
It is called a spacetime cloak because the data is transported in a 'bubble of time.'
The piece above the water's surface would appear below the water and leaning in the opposite direction.
In a more futuristic scenario, a person looking at a person wearing a cloak with artificially designed refraction properties would see part or none of the person.
This would, however, depend on the cloak's refractive index and whether the light bouncing off of it reached the viewer's eye.
But metamaterials with this negative refraction have presented a vexing physics problem: They reduce the strength of the wave.
'One of the biggest problems with metamaterials is that they produce energy loss,' Professor Xin said.
'The waves decay as they pass through the artificial material. We have designed a metamaterial that retains negative refraction but does not diminish energy.'
In fact, the synthetic material not only prevented energy loss - it caused energy gain, with the microwave intensifying in strength as it passed through the material.
Professor Xin achieved this by embedding battery-powered tunnel diodes – which is a type of semiconductor device - and into the new material.
'Many people did not think it was possible to achieve energy gain along with negative refraction,' Professor Xin said.
He first showed it was possible, with one-dimensional metamaterials, in a paper published in Physical Review Letters in 2011.
His new findings, reported in Nature Communications, have broader implications, because they involve 3D metamaterials.
Professor Xin said it will be years before fantastical applications like a Harry Potter-style invisibility cloaks would appear on the market.
But he says his research is inherently practical, predicting: 'Invisibility cloaks will be a reality in my lifetime.'
Professor Xin said it will be years before fantastical applications like invisibility cloaks appear on the market. But his research is practical, he said, predicting: 'Invisibility cloaks will be a reality in my lifetime'