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Harry Potter–Style ‘Moving Invisibility Cloak’ Technology Developed
<(Top row, left) Ph.D candidate Hyeonseung Lee, Professor Wonho Choe, (Second row, left) Professor Hyoungsoo Kim, Professor Sanghoo Park,(Top) First author Dr. Jeongsu Pyeon>
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, our research team has taken it one step further by developing a “smart invisibility cloak” like 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.
On December 16th, 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 announced that they 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.
* Cloaking: A technology that makes an object appear as if it does not exist to detection equipment such as radar or sensors, even though it is physically present.
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.
The liquid metal composite ink developed by the research team maintains electrical conductivity even when stretched up to 12 times its original length (1200%), 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.
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.
<Figure. Comparison of LMCP ink properties, printing process applicability, mechanical/electrical performance, and versatility on various substrates.
(a) Comparison results regarding surface tension, viscosity, wettability, and post-processing requirements between conventional liquid metal-based inks and the LMCP ink in this study. The results demonstrate that LMCP ink possesses the advantage of requiring no post-processing while maintaining relatively high viscosity and excellent wettability. (Right radar chart: Qualitative comparison of key performance indicators, including electrical conductivity, surface tension, viscosity, wettability, and post-processing requirements).
(b) Various printing methods based on the self-sintering characteristics of LMCP ink: nozzle-based direct writing, brushing, patterning using shadow masks and doctor blade processes, and large-area electrode fabrication via the roll-to-roll method.
(c) Stretchability and electrical stability of LMCP electrodes. Results show resistance changes when samples are stretched from 0% to 1200%, and stable operation is confirmed under 0%–500% strain through a 3 V LED driving experiment.
(d) Examples of various patterns and devices fabricated using LMCP ink. Applicable structures are presented, including large-area uniform coating, precise grid patterns, crack-free metal paths, LED circuits operating under tension, and stretchable spiral electrodes>
(e) Examples demonstrating stable printing of LMCP ink on various substrates (SIR, NBR, PVC, PET, WPU, PDMS, Latex), indicating excellent pattern reproducibility and adhesion regardless of the substrate type>
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.”
This research was recognized as an important fundamental technology in the field of next-generation electronic materials and was published in the October 2025 issue of the international Wiley journal Small on October 16, where it was selected as a cover article.
Paper title:
J. Pyeon, H. Lee, W. Choe, S. Park, H. Kim,
“Versatile Liquid Metal Composite Inks for Printable, Durable, and Ultra-Stretchable Electronics,”
Small 2501829 (2025)
DOI: https://doi.org/10.1002/smll.202501829
Author information:
First author: Dr. Jeongsu Pyeon
Co-authors: Doctoral candidate Hyeonseung Lee, Professor Wonho ChoeCorresponding authors: Professor Hyoungsoo Kim, Professor Sanghoo Park
This work was supported by the National Research Foundation of Korea’s Mid-Career Research Program (MSIT: 2021R1A2C2007835) and the KAIST UP Program.
< Selected as the cover article of the October 2025 issue of the international journal Small >
< Invisibility cloak technology image (AI-generated image) >
2025.12.16 View 2905 -
First Instance of Negative Effects from Terahertz-Range Electromagnetic Waves
Professor Philhan Kim
Electromagnetic waves (EM-wave) in the terahertz range were widely regarded as the “dream wavelength” due to its perceived neutrality. Its application was also wider than X-rays. However, KAIST scientists have discovered negative effects from terahertz EM-waves.
Professor Philhan Kim of KAIST’s Graduate School of Nanoscience and Technology and Dr. Young-wook Jeong of the Korea Atomic Energy Research Institute (KAERI) observed inflammation of animal skin tissue when exposed to terahertz EM-waves.
The results were published in the online edition of Optics Express (May 19, 20104).
Terahertz waves range from 0.1 to 10 terahertz and have a longer wavelength than visible or infrared light. Commonly used to see through objects like the X-ray, it was believed that the low energy of terahertz waves did not inflict any harm on the human body.
Despite being applied for security checks, next-generation wireless communications, and medical imaging technology, little research has been conducted in proving its safety and impact. Conventional research failed to predict the exact impact of terahertz waves on organic tissues as only artificially cultured cells were used.
The research team at KAERI developed a high power terahertz EM-wave generator that can be used on live organisms. A high power generator was necessary in applications such as biosensors and required up to 10 times greater power than currently used telecommunications EM-wave. Simultaneously, a KAIST research team developed a high speed, high resolution video-laser microscope that can distinguish cells within the organism.
The experiment exposed 30 minutes of terahertz EM-wave on genetically modified mice and found six times the normal number of inflammation cells in the skin tissue after six hours. It was the first instance where negative side effects of terahertz EM-wave were observed.
Professor Kim commented that “the research has set a standard for how we can use the terahertz EM-wave safely” and that “we will use this research to analyze and understand the effects of other EM-waves on organisms.”
2014.06.20 View 13263 -
Professor Chung-Seok Chang named as APS Fellow
Professor Chung-Seok Chang named as APS Fellow
- Honorable position offered only to an extremely small number of members within 0.5% of APS
- Recognized for his leading and creative contribution to Plasma conveyance theory, Electromagnetic waves heating theory and leadership in the research field of large-scaled computer simulation
Professor Chung-Seok Chang (Department of Physics) was named as a fellow of the American Physics Society (APS), world-renowned society in the physics filed.
The fellow of the APS is considered as a position of great honor among scholars in the field of Physics since only a small number of regular members within 0.5% of the APS can become the fellows. Professor Chang was recognized for his leading and creative contribution to the fields of Plasma conveyance theory, Electromagnetic waves heating theory and leadership in the research field of large-scaled computer simulation, which made him named as APS fellow.
Professor Chang has been invited several times to the Main Policy Committee of the U.S. Department of Energy and was a member of On-site Review Committee on the theoretical research activities of the U.S. major state-run institutes. Due to many world-recognized research results carried out with KAIST students, he has been invited several times for lecture to the conference of the APS as well as large-scaled international academic conferences. As a result, KAIST doctorates of Computational Physics from his laboratory are recognized globally for their excellence in the field of nuclear fusion.
Besides, Professor Chang was assigned as the Chief General of the super-sized Computational Theory Research Group last year, to which the U.S Department of Energy will invest 6 million dollars of research fund for three years, and manages the complex theory research group that transcribes and reproduces the properties of nuclear fusion plasma by using large-scaled parallel computers with its head quarter in the U.S. Courant Institute of Mathematical Sciences. This research group consists of greatest U.S. scholars in the fields of Physics, Mathematics, and Computation, belonging to 14 research-education institutes such as Princeton University, Colombia University, MIT, University of California Engineering College, California State University, Rutgers University, New-York University, Courant Institute of Mathematical Sciences, Oak Ridge National Lab, Berkeley National Laboratories, etc., thereby gathering worldwide
2006.10.25 View 18847