New Meta-Skin Is Invisible To Radio Waves

This flexible, stretchable and tunable 'meta-skin' can trap radar waves and cloak objects from detection. Liang Dong/Iowa State University

Invisibility cloaks might still be a fantasy, but scientists are studying new materials that could one day make them a reality. And the applications go beyond sneaking around Hogwarts at night.

Iowa State University engineers have created a flexible metamaterial that uses rows of small liquid-metal devices that can absorb and trap a wide range of radio frequencies. The meta-skin is made from a polymer with small rings within, and it can suppress up to 75 percent of radio waves between 8 and 10 gigahertz.

"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, published in Scientific Reports.

“Recently, inclusion of liquid metal as active components has opened up new ways to realize stretchable and flexible electronics.”

The meta-skin is made of silicone sheets filled with Galinstan, a non-toxic liquid metal alloy made of gallium, indium, and tin. The team constructed rows of split rings; the liquid wire ring itself becomes an electric inductor and the gaps create capacitors, so together they act as a resonator that traps and suppresses radar waves at a certain frequency.

This technology reduces the radio waves in all incident directions and observation angles, not just the waves reflected back to a probing radar like that used in the Stealth Bomber. By altering the size and position of the metal rings, the meta-skin can tune out a large amount of frequency, although nothing close to visible light.

"The long-term goal is to shrink the size of these devices," Professor Liang Dong, coauthor of the paper, said in a statement. "Then hopefully, we can do this with higher-frequency electromagnetic waves such as visible or infrared light.

"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."

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