If you want to fly under the radar, you could do with a sheet of this material. Using a series of liquid-metal absorbers, the new film can soak up radar in order to cloak whatever it happens to be covering. Developed by researchers from Iowa State University, the material is made up of a series of liquid metal split-ring resonators embedded within a flexible sheet of silicone. Each of the rings has a radius of just a quarter of a centimetre, and its narrow circumference is filled with the liquid metal galinstan. This creates a series of short liquid wires that cover the entire surface of the film.
These rings act as electrical inductors and the gaps between them as capacitors. When a radar wave of the correct frequency hits the surface, it sets up oscillating electrical signals in these simple components, in turn dumping its energy. In other words, it's absorbed by the film.
This only happens if the frequency of the radar wave corresponds to the geometry of the rings — but because the material is flexible it can be deformed, allowing the researchers to tune the material to absorb different signals. In fact, the team has shown that it can use the same sheet of material to absorb 75 per cent of radar signals across the entire frequency range between 8 and 10 gigahertz. The research is published in Scientific Reports.
The team reckons the material could be used in military applications, to cloak objects from radar detection. But it also reckons that the same concept could be applied to signals including visible or infrared light to create optical cloaking devices too — though it would require some very delicate construction methods, as the same geometries would have to be recreated on the nanoscale instead.
Image by Liang Dong/Iowa State University