Harry Potter-style 'moving invisibility cloak' technology developed - Electronics & Semiconductors - Hi Tech & Innovation

Credit: Cover, Small (2025). DOI: 10.1002/smll.202501829

What do Harry Potter's invisibility cloak and stealth fighter jets that evade radar have in common? They both make objects invisible despite their physical presence. Building upon this concept, a research team has taken it one step further by developing a "smart invisibility cloak" technology that hides electromagnetic waves even better as it stretches and moves. This technology is expected to open new possibilities for moving robots, body-mounted wearable devices, and next-generation stealth technologies.

Breakthrough in stretchable cloaking technology

Research teams led by Professor Hyoungsoo Kim of the Department of Mechanical Engineering and Professor Sanghoo Park of the Department of Nuclear and Quantum Engineering from KAIST have developed a core enabling technology for next-generation stretchable cloaking based on Liquid Metal Composite Ink (LMCP), which can absorb, modulate, and shield electromagnetic waves. This research was published in the October 2025 issue of Small, where it was selected as a cover article.

To realize cloaking technology, it is necessary to freely control light or electromagnetic waves on the surface of an object. However, conventional metallic materials are rigid and do not stretch well, and when forcibly stretched, they easily break. For this reason, there have been significant difficulties in applying such materials to body-conforming electronic devices or robots that freely change shape.

Comparison of LMCP ink properties, printing process applicability, mechanical/electrical performance, and versatility on various substrates. Credit: Adapted from Small (2025). DOI: 10.1002/smll.202501829

The liquid metal composite ink developed by the research team maintains electrical conductivity even when stretched up to 12 times its original length (1,200%), and it demonstrated high stability with little oxidation or performance degradation even after being left in air for nearly a year. Unlike conventional metals, this ink is rubber-like and soft while fully retaining metallic functionality.

These properties are possible because, during the drying process, liquid metal particles inside the ink spontaneously connect with one another to form a mesh-like metallic network structure. This structure functions as a "metamaterial"—an artificial structure in which extremely small patterns are repeatedly printed using ink so that electromagnetic waves interact with the structure in a designed manner. As a result, the material simultaneously exhibits liquid-like flexibility and metal-like robustness.

The fabrication process is also simple. Without complex procedures such as high-temperature sintering or laser processing, the ink can be printed using a printer or applied with a brush and then simply dried. In addition, common drying issues such as stains or cracking do not occur, enabling smooth and uniform metal patterns.

Demonstrating and evaluating the new material

To verify the performance of the ink, the research team became the first in the world to fabricate a "stretchable metamaterial absorber" whose electromagnetic wave absorption characteristics change depending on the degree of stretching.

Simply stretching the rubber-like substrate after printing patterns with the ink changes the type (frequency band) of electromagnetic waves that are absorbed. This demonstrates the potential for cloaking technology that can more effectively hide objects from radar or communication signals depending on the situation.

This technology is evaluated as a groundbreaking electronic material technology that simultaneously satisfies stretchability, electrical conductivity, long-term stability, process simplicity, and electromagnetic wave control functionality.

Professor Hyoungsoo Kim stated, "We have made it possible to implement electromagnetic wave functionality using only printing processes without complex equipment," adding, "This technology is expected to be utilized in various future technologies such as robotic skin, body-mounted wearable devices, and radar stealth technologies in the defense sector." 

Provided by The Korea Advanced Institute of Science and Technology (KAIST) 

by The Korea Advanced Institute of Science and Technology (KAIST)

edited by Lisa Lock, reviewed by Robert Egan 

Source: Harry Potter-style 'moving invisibility cloak' technology developed