The research was announced on December 16 by the Korea Advanced Institute of Science and Technology (KAIST). The study was led by Professor Kim Hyung-soo of the Department of Mechanical Engineering and Professor Park Sang-hoo of the Department of Nuclear and Quantum Engineering.
The concept behind cloaking technology is to make an object undetectable to radar or sensors by controlling how electromagnetic waves, such as radio waves, interact with its surface. While cloaking has long been studied in theory and in rigid materials, applying it to moving or flexible objects has remained difficult because conventional metals conduct electricity well but break easily when stretched.
The KAIST team addressed this limitation by developing a liquid metal composite ink, known as LMCP, that maintains electrical conductivity even when stretched up to 12 times its original length. The ink also showed high durability, remaining stable in open air for nearly a year without significant corrosion or performance loss.
Unlike solid metals, the ink behaves like rubber while retaining metallic conductivity. This is possible because liquid metal particles inside the ink naturally form a network-like structure as the material dries, creating a self-connected conductive pathway. When printed in repeating microscopic patterns, the structure functions as a type of metamaterial, an engineered material designed to manipulate electromagnetic waves in specific ways.
Using this ink, the researchers demonstrated the world's first stretchable electromagnetic metamaterial absorber whose radar absorption properties change depending on how much it is stretched. Simply pulling the material like a rubber band altered the frequency range of electromagnetic waves it could absorb, showing that cloaking performance could be actively tuned through physical deformation.
The fabrication process is also relatively simple. The ink can be printed or brushed onto a surface and dried without the need for high-temperature processing, lasers, or complex manufacturing equipment. It also avoids common problems seen in liquid-based materials, such as cracking or uneven drying, allowing for smooth and uniform metal patterns.
According to the researchers, the technology could be applied to robot skins that move and deform, body-worn electronic devices, and next-generation stealth systems that require adaptability rather than fixed shapes. By allowing cloaking performance to respond dynamically to movement, the material opens possibilities that were previously difficult to achieve with rigid designs.
Professor Kim said the research shows that advanced electromagnetic functions can be realized through simple printing processes without complex machinery. He added that the technology could serve as a foundation for future applications ranging from wearable electronics to radar stealth systems.
The findings were published in the October 2025 issue of the international journal Small, published by Wiley, and were selected as a cover article. The study was supported by a mid-career research grant from the National Research Foundation of Korea and the KAIST UP Program.
The research team included first author Dr. Pyeon Jeong-su, co-author Lee Hyunseung, and Professor Choi Won-ho, with Professors Kim Hyungsoo and Park Sang-hoo serving as corresponding authors.
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