The idea might seem to belong in Harry Potter, but invisibility cloaks could soon be found in real life.
A group of engineers has invented a flexible, stretchable material that can hide an object from the eyes of radar detectors.
The so-called 'meta material' could coat the surface of the next-generation of stealth aircraft and the researchers are hoping to extend its 'cloaking' properties to include visible light, too.
Radar is a way of detecting objects using radio waves or microwaves.
The waves are transmitted by the device and objects in their path reflect them back to the radar receiver, which can tell how far away the objects are or how fast they are moving.
The technology is used for detecting aircraft, spaceships, motor vehicles and missiles, for example.
The new metamaterial-based skin, or 'meta-skin', developed by a group from Iowa State University, is a kind of radar invisibility cloak that will trap radio or microwaves so would not show up under a radar detector.
The idea of an invisibility cloak might seem to belong in Harry Potter (scene pictured) but soon it could be found in real life after researchers designed a new 'meta-skin'. The material can hide from radar detectors and one day, the researchers said, they hope it will work on visible light
The liquid-filled rings in the meta-skin create electric inductors, which resist changes in current passing through them, and the gaps create capacitors.Stretching the material changes the size of the liquid metal rings inside, so changes the frequency the devices suppress
It can be tuned to the specific wavelength of electromagnetic waves by stretching and flexing the skin.
The cloak is made from metamaterials, the name for composite materials that have properties not found in nature.
The specific metamaterials used for the cloak can manipulate electromagnetic waves.
'It is believed that the present meta-skin technology will find many applications in electromagnetic frequency tuning, shielding and scattering suppression,' the engineers wrote in their paper.
The material is made up of rows of rings, with a radius of 0.1 inches (2.5mm) and gaps of 0.04 inches (1mm), filled with a metal alloy that is a liquid at room temperature called galinstan.
The diagram shows the experimental setup for measuring the radar detected from a nylon rod wrapped in the new meta-skin.
The diagram shows the fabrication process flow for the meta-skin. The material can trap radar waves and one day, the researchers said, the meta-skin could coat the surface of the next generation of stealth aircrafts
The rings create electric inductors, which resist changes in current passing through them, and the gaps create capacitors, which store electrical energy in a temporary electric field.
Together they create a resonator that can trap and suppress radar waves at a certain frequency.
Stretching the material changes the size of the liquid metal rings inside, so changes the frequency the devices suppress.
In the range of frequency between 8 and 10 GHz, part of the spectrum used for things like cable and satellite TV and radar devices, the material suppressed about 75 per cent of the radar waves
INVISIBILITY CLOAKS IN THE MOVIES
- In Harry Potter, Dumbledore returns Harry's father's invisibility cloak to Harry as a Christmas present during his first year at Hogwarts.
Harry uses the cloak throughout the series to sneak around the school.
- In 2002 Bond film Die Another Day, Bond's Aston Martin V12 Vanquish, can become invisible.
- Its "adaptive camouflage" cloaking system, allowed Pierce Brosnan to press a button and disappear his speedster, at least to the naked eye.
- And, although not technically a cloak, in J.R.R. Tolkien's Lord of the Rings films, after being introduced in The Hobbit the ring of power makes those that wear it invisible.
In the range of frequency between 8 and 10 GHz, part of the super high frequency radio waves used for things like cable and satellite TV, microwave cookers, amateur radio and most modern radar devices, the material suppressed about 75 per cent of the radar waves.
'This meta-skin technology is different from traditional stealth technologies that often only reduce the backscattering, i.e., the power reflected back to a probing radar,' the paper said.
One day, the researchers explained, the meta-skin could coat the surface of the next generation of stealth aircraft.
They also hope in the long term that the devices will be able to be used on higher frequency electromagnetic waves, such as visible light or infrared, making a real invisibility cloak.
'While that would require advanced nanomanufacturing technologies and appropriate structural modifications, we think this study proves the concept of frequency tuning and broadening, and multidirectional wave suppression with skin-type metamaterials,' said Liang Dong, lead author of the paper. dailymail