New stretchy 'meta-skin' to cloak objects from radars

Scientists have developed a new flexible, stretchable and tunable "meta-skin" that can protect objects from radar detection, and may help develop next generation of stealth aircraft or even invisibility cloaks.
The meta-skin takes its name from metamaterials, which are composites that have properties not found in nature and that can manipulate electromagnetic waves.
By stretching and flexing the polymer meta-skin, it can be tuned to reduce the reflection of a wide range of radar frequencies.
"It is believed that the present meta-skin technology will find many applications in electromagnetic frequency tuning, shielding and scattering suppression," said researchers from Iowa State University.

The researchers wanted to prove that electromagnetic waves - perhaps even the shorter wavelengths of visible light - can be suppressed with flexible, tunable liquid-metal technologies.
They came up with rows of split ring resonators embedded inside layers of silicone sheets. The electric resonators are filled with galinstan, a metal alloy that is liquid at room temperature and less toxic than other liquid metals such as mercury.

Those resonators are small rings with an outer radius of 2.5 millimetres and a thickness of half a millimetre. They have a 1 millimetre gap, essentially creating a small, curved segment of liquid wire.

The rings create electric inductors and the gaps create electric capacitors. Together they create a resonator that can trap and suppress radar waves at a certain frequency.
Stretching the meta-skin changes the size of the liquid metal rings inside and changes the frequency the devices suppress.
Tests showed radar suppression was about 75 per cent in the frequency range of 8 to 10 gigahertz, researchers said.
When objects are wrapped in the meta-skin, the radar waves are suppressed in all incident directions and observation angles.
"Therefore, this meta-skin technology is different from traditional stealth technologies that often only reduce the backscattering, ie, the power reflected back to a probing radar," the researchers said.

The meta-skin could in future coat the surface of the next generation of stealth aircraft, said lead author Jiming Song, professor at Iowa State University.
The researchers are even hoping to develop a cloak of invisibility using the technology in future.
"The long-term goal is to shrink the size of these devices," said Liang Dong, from Iowa State University.
"Then hopefully we can do this with higher-frequency electromagnetic waves such as visible or infrared light," Dong said.
The study was published in the journal Scientific Reports.