Researchers in South Korea have developed a “smart invisibility cloak” that hides electromagnetic waves while stretching and moving, a technology that is expected to open up new possibilities for robots, wearables and next-generation stealth technology in the defense sector.
Researchers in South Korea have developed a “smart invisibility cloak” that hides electromagnetic waves while stretching and moving, a technology that is expected to open up new possibilities for robots, wearables and next-generation stealth technology in the defense sector.
A research group at KAIST has developed a basic technology for creating next-generation elastic masking. The development is based on liquid metal composite inks (LMCPs) that can absorb, modulate, and shield electromagnetic waves, Tech Xplore reports .
To implement cloaking technology, it is necessary to freely control the light or electromagnetic waves on the surface of the object. However, ordinary metal materials are rigid and do not stretch well, and they are easy to break when stretched strongly. For this reason, it has been difficult to apply such materials to electronic devices that adapt to the body or robots that freely change shape.
The liquid metal composite ink developed by the research team retains electrical conductivity even when stretched to 12 times its original length (1200%). The material has demonstrated high stability: it hardly oxidizes and does not lose its characteristics even after being exposed to the open air for almost a year. Unlike conventional metals, this ink is soft and elastic, like rubber, while fully retaining the functions of a metal.
These properties are made possible because, as the liquid metal particles inside the ink dry, they spontaneously bond together to form a mesh-like metallic structure. This structure functions as a “metamaterial”—an artificial structure in which extremely small patterns are repeatedly applied with ink so that electromagnetic waves interact with them in a predetermined way. The result is a material that simultaneously exhibits the flexibility of a liquid and the strength of a metal.
The manufacturing process is also simple. Without complicated procedures such as high-temperature sintering or laser processing, the ink can be printed with a printer or applied with a brush and then simply dried. In addition, there are no common drying problems such as spots or cracking, ensuring smooth and uniform metal patterns.
To test the ink's performance, the research team became the first in the world to fabricate an "elastic metamaterial absorber" whose electromagnetic wave absorption characteristics change depending on the degree of stretching.
Simply stretching a rubber-like substrate with a patterned surface changes the type (frequency range) of electromagnetic waves absorbed, demonstrating the potential of cloaking technology to more effectively hide objects from radar or communications signals, depending on the situation.
This technology is being hailed as a breakthrough in the field of electronic materials because it simultaneously combines elasticity, electrical conductivity, long-term stability, ease of production, and the function of controlling electromagnetic waves.
