Engineers may have developed a new kind of "invisibility cloak" for objects against radar waves. They've created a flexible skin that traps radar waves and cloaks objects.

The new 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," the Iowa State University engineers who created the material wrote in their paper.

In this latest effort, the researchers wanted to prove that electromagnetic waves could be suppressed with flexible, tunable liquid-metal technologies. They eventually came up with rows of split ring resonators embedded inside layers of silicone sheets. The electric resonators were filled with galinstan, a metal alloy that's liquid at room temperature and less toxic than other liquid metals such as mercury.

The resonators themselves are small rings with an outer radius of 2.5 millimeters and a thickness of half a millimeter. They have a 1-millimeter 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 actually changes the size of the liquid metal rings inside and changes the frequency that the devices suppress.

Tests showed that radar suppression was about 75 percent in the frequency range of 8 to 10 gigahertz. When objects are wrapped in the meta-skin, though, 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, i.e., the power reflected back to a probing radar," wrote the engineers.

The findings could be huge for next generation stealth aircraft and other stealth-based vehicles and equipment that needs to be hidden.

Currently, though, the researchers are putting their focus into a cloak of invisibility for the future.