KAIST researchers unveil durable radar stealth ink

Korean researchers have developed a foundational technology that could turn the invisibility cloak popularized in the Harry Potter films into reality. The breakthrough is expected to open new possibilities in fields such as robotics and unmanned aerial vehicles and could pave the way for stealth systems capable of evading detection by radar or other sensors.

KAIST said on Dec. 16 that research teams led by Professor Kim Hyeong-su of the Department of Mechanical Engineering and Professor Park Sang-hoo of the Department of Nuclear and Quantum Engineering have developed a liquid metal composite ink that enables the fabrication of an invisibility cloak undetectable by radar. The study was selected as the cover article for the October issue of the international academic journal Small.

Radar systems determine a target’s position by transmitting radio waves and analyzing the signals reflected back to the receiver. In practical terms, evading radar detection requires preventing those reflected waves from returning to the radar system. The newly developed liquid metal composite ink absorbs electromagnetic waves, rendering objects effectively invisible to radar.

Earlier attempts to develop radar-stealth materials faced major technical hurdles. Conventional liquid metals oxidized quickly when exposed to air, leading to a rapid decline in performance. Much like an oil film spreading across the surface of water droplets, an oxide layer formed almost immediately on liquid metal particles. This process disrupted connections between particles and accelerated corrosion.

The newly developed liquid metal composite ink allows liquid metal particles to connect spontaneously as it dries, forming a mesh-like structure. Experiments conducted by the research team showed that the structure remained highly stable, maintaining its performance for more than a year without signs of corrosion. It also retained electrical conductivity even when stretched to 12 times its original length. The researchers said the material is soft and flexible like rubber while fully preserving the functional properties of metal.

The manufacturing process is relatively simple. The ink can be printed using a standard printer or applied with a brush and then left to dry under ambient conditions.

The liquid metal composite ink is expected to have applications across a wide range of weapons systems that require radar stealth technology. It could also serve as a material for electronic devices, including wearable technologies. For example, applying the ink to folding sections of foldable smartphones could help maintain structural stability while allowing repeated bending. Professor Kim said the team succeeded in implementing electromagnetic wave functionality through a printing process alone, without the need for complex equipment, adding that the technology is expected to find broad use in future applications.


최지원 jwchoi@donga.com