A new flexible, stretchable ‘metaskin’ has been developed by American engineers that can make objects invisible to a wide range of radar frequencies.
The skin is made of metamaterials, composites with properties not naturally present in nature. By stretching and flexing the polymer-based skin, engineers can manipulate its ability to reflect electromagnetic waves and reduce it to minimum.
"It is believed that the present metaskin technology will find many applications in electromagnetic frequency tuning, shielding and scattering suppression," the research team from Iowa State University wrote in a paper published recently in the journal Scientific Reports.
The skin, which consists of rows of small liquid-metal devices, can be used to cover an object that needs to be hidden from radar. The small liquid-metal devices - known as split-ring resonators - are embedded in layers of silicone sheets. Only half a millimetre thick, the resonators are filled with galinstan, a type of metal alloy that is liquid at room temperature, thus allowing the skin to be stretched and bent.
Between each two resonators is a gap of one millimetre, which functions as a liquid wire. Together, they can trap and suppress radar waves at a certain frequency. Stretching the metaskin changes the size of the liquid metal rings inside and changes the frequency the devices suppress.
"This metaskin technology is different from traditional stealth technologies that often only reduce the backscattering, i.e. the power reflected back to a probing radar," the engineers wrote in their paper.
Tests showed radar suppression was about 75 per cent in the frequency range of 8 to 10 gigahertz, according to the paper. When objects are wrapped in the metaskin, the radar waves are suppressed in all incident directions and observation angles.
In future, such a skin could be used to protect fighter jets. The research team was led by associated professor Liang Dong and professor Jiming Song.
"The long-term goal is to shrink the size of these devices," Dong said. "Then hopefully we can do this with higher-frequency electromagnetic waves such as visible or infrared light. While that would require advanced nano-manufacturing 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."