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A Breakthrough Concept in Nano-Printing Technology
<(From Left) Professor Inkyu Park, Ph.D candidate Byung-Ho Kang, Researcher Jun-Ho Jeong, Professor Junseong Ahn>
A breakthrough technology has been developed that allows metal circuits floating on water to be transferred directly onto any desired surface. A South Korean research team has introduced a novel technique capable of transferring ultra-fine nano-circuits onto plant leaves and fruits, as well as curved automotive surfaces and robot exteriors, all without causing any damage. This technology is expected to be widely utilized across various cutting-edge industries, including smart agriculture, wearable healthcare, and bioelectronics.
KAIST announced on June 15th that a joint research team led by Distinguished Professor Inkyu Park from the Department of Mechanical Engineering, Dr. Jun-Ho Jeong from the Korea Institute of Machinery and Materials and Professor Junseong Ahn from Korea University has successfully developed "Water-Floating Nano-Transfer Printing (WF-nTP)." This technology enables precision metal thin films floated on water to be transferred onto various 3D surfaces.
Conventional nano-transfer printing (nTP), which is widely used to manufacture electronic devices and sensors, typically requires high heat, intense pressure, adhesives, or toxic chemical solvents. Consequently, applying this method to biological tissues or complex curved surfaces that are sensitive to heat and pressure has proven highly challenging.
To overcome these limitations, the research team proposed a completely new approach: floating metal circuits on the surface of water.
Fabrication: The team deposited an ultra-thin layer of metals such as gold (Au), platinum (Pt), palladium (Pd), or nickel (Ni) onto a polymer mold.
Separation: They then used plasma gas which has a high-energy state of ionized gas to selectively remove (etch) a part of the mold.
Floating: When this structure is placed in water, water infiltrates through the microscopic gaps, causing the 20-nanometer (nm) thick metal film to float to the surface on its own while perfectly maintaining its original shape.
<Overview of the water-floated nano mesh and versatile transfer technique>
The research team transferred the metal circuits using a "scooping" method, which involves submerging the target object beneath the floating film and slowly lifting it upward. As the water evaporates, capillary force (the force that moves liquid through narrow spaces) tightly adheres the circuit to the surface. Once the water completely dries, intermolecular forces come into play, securing the circuit firmly in place without the need for any adhesive.
Notably, the team also succeeded in transferring circuits onto hydrophobic (water-repellent) surfaces, such as lotus leaves. By adding a small amount of ethanol to the water to lower its surface tension (the property of a liquid surface that causes it to shrink), they effectively overcame a major limitation of conventional technologies.
This technology holds immense potential for widespread application because it can adapt to diverse surfaces while flawlessly preserving the nano-patterns. Using this method, the research team fabricated Surface-Enhanced Raman Scattering (SERS) sensors which are used for high-sensitivity detection of trace chemical substances and attached them directly to plant leaves and fruit surfaces. Through this, they successfully detected thiram, a pesticide component, on the surfaces of leaves and fruits. Furthermore, they successfully implemented a wearable, high-performance hydrogen gas sensor by transferring a palladium (Pd) mesh onto highly flexible thermoplastic polyurethane (TPU) fibers.
<Research Image(AI-generated)>
Distinguished Professor Inkyu Park stated: "This technology is highly significant as it shatters the substrate limitations of conventional nano-transfer printing, allowing nano-patterns to be transferred onto sensitive surfaces like living plant leaves or human skin without heat or adhesives. We expect it to evolve into a core platform technology for wearable sensors and bioelectronics, finding applications in smart agriculture for pesticide detection without damaging crops, wearable health monitoring devices, bioelectronic devices, and electronic skins for next-generation robots."
This research, with PhD student Byung-Ho Kang from the KAIST Department of Mechanical Engineering participating as the first author, was published online on March 30, 2026, in the prestigious international academic journal Nature Communications.
The study authors include Byung-Ho Kang, Ji-Hwan Ha, Yeongjae Kwon, Sohee Jeon, Donho Lee, Byeongmin Kang, Soon Hyoung Hwang, Junseong Ahn, Jun-Ho Jeong, and Inkyu Park.
Meanwhile, this research was conducted with funding from the Ministry of Science and ICT through the National Research Foundation of Korea (NRF) Mid-Career Researcher Support Program, and the Ministry of Trade, Industry and Energy through the Korea Evaluation Institute of Industrial Technology (KEIT) Alchemist Project.
2026.06.15 View 2670 -
Synthesizing Single-Crystalline Hexagonal Graphene Quantum Dots
(Figure: Uniformly ordered single-crystalline graphene quantum dots of various sizes synthesized through solution chemistry.)
A KAIST team has designed a novel strategy for synthesizing single-crystalline graphene quantum dots, which emit stable blue light. The research team confirmed that a display made of their synthesized graphene quantum dots successfully emitted blue light with stable electric pressure, reportedly resolving the long-standing challenges of blue light emission in manufactured displays. The study, led by Professor O Ok Park in the Department of Chemical and Biological Engineering, was featured online in Nano Letters on July 5.
Graphene has gained increased attention as a next-generation material for its heat and electrical conductivity as well as its transparency. However, single and multi-layered graphene have characteristics of a conductor so that it is difficult to apply into semiconductor. Only when downsized to the nanoscale, semiconductor’s distinct feature of bandgap will be exhibited to emit the light in the graphene. This illuminating featuring of dot is referred to as a graphene quantum dot.
Conventionally, single-crystalline graphene has been fabricated by chemical vapor deposition (CVD) on copper or nickel thin films, or by peeling graphite physically and chemically. However, graphene made via chemical vapor deposition is mainly used for large-surface transparent electrodes. Meanwhile, graphene made by chemical and physical peeling carries uneven size defects.
The research team explained that their graphene quantum dots exhibited a very stable single-phase reaction when they mixed amine and acetic acid with an aqueous solution of glucose. Then, they synthesized single-crystalline graphene quantum dots from the self-assembly of the reaction intermediate. In the course of fabrication, the team developed a new separation method at a low-temperature precipitation, which led to successfully creating a homogeneous nucleation of graphene quantum dots via a single-phase reaction.
Professor Park and his colleagues have developed solution phase synthesis technology that allows for the creation of the desired crystal size for single nanocrystals down to 100 nano meters. It is reportedly the first synthesis of the homogeneous nucleation of graphene through a single-phase reaction.
Professor Park said, "This solution method will significantly contribute to the grafting of graphene in various fields. The application of this new graphene will expand the scope of its applications such as for flexible displays and varistors.”
This research was a joint project with a team from Korea University under Professor Sang Hyuk Im from the Department of Chemical and Biological Engineering, and was supported by the National Research Foundation of Korea, the Nano-Material Technology Development Program from the Electronics and Telecommunications Research Institute (ETRI), KAIST EEWS, and the BK21+ project from the Korean government.
2019.08.02 View 43935 -
Professor Keon-Jae Lee Lectures at IEDM and ISSCC Forums
Professor Keon-Jae Lee of KAIST’s Materials Science and Engineering Department delivered a speech at the 2015 Institute of Electrical and Electronics Engineers (IEEE) International Electron Devices Meeting (IEDM) held on December 7-9, 2015 in Washington, D.C.
He will also present a speech at the 2016 International Solid-State Circuits Conference scheduled on January 31-February 4, 2016 in San Francisco, California.
Both professional gatherings are considered the world’s most renowned forums in electronic devices and semiconductor technology. It is rare for a Korean researcher to be invited to speak at these global conferences.
Professor Lee was recognized for his research on flexible NAND chips. The Korea Times, an English language daily newspaper in Korea, reported on his participation in the forums and his recent work. An excerpt of the article follows below:
“KAIST Professor to Lecture at Renowned Tech Forums”
By Lee Min-hyung, The Korea Times, November 26, 2015
Recently he has focused on delivering technologies for producing flexible materials that can be applied to everyday life. The flexible NAND flash memory chips are expected to be widely used for developing flexible handsets. His latest research also includes flexible light-emitting diodes (LED) for implantable biomedical applications.
Lee is currently running a special laboratory focused on developing new flexible nano-materials. The research group is working to develop what it calls “self-powered flexible electronic systems” using nanomaterials and electronic technology.
Lee’s achievement with flexible NAND chips was published in the October edition of Nano Letters, the renowned U.S.-based scientific journal.
He said that flexible memory chips will be used to develop wearable computers that can be installed anywhere.
2015.11.26 View 20639 -
KAIST Develops a Method to Transfer Graphene by Stamping
Professor Sung-Yool Choi’s research team from KAIST's Department of Electrical Engineering has developed a technique that can produce a single-layer graphene from a metal etching. Through this, transferring a graphene layer onto a circuit board can be done as easily as stamping a seal on paper.
The research findings were published in the January 14th issue of Small as the lead article.
This technology will allow different types of wafer transfer methods such as transfer onto a surface of a device or a curved surface, and large surface transfer onto a 4 inch wafer. It will be applied in the field of wearable smart gadgets through commercialization of graphene electronic devices.
The traditional method used to transfer graphene onto a circuit board is a wet transfer. However, it has some drawbacks as the graphene layer can be damaged or contaminated during the transfer process from residue from the metal etching. This may affect the electrical properties of the transferred graphene.
After a graphene growth substrate formed on a catalytic metal substrate is pretreated in an aqueous poly vinyl alcohol (PVA) solution, a PVA film forms on the pretreated substrate. The substrate and the graphene layers bond strongly. The graphene is lifted from the growth substrate by means of an elastomeric stamp.
The delaminated graphene layer is isolated state from the elastomeric stamp and thus can be freely transferred onto a circuit board. As the catalytic metal substrate can be reused and does not contain harmful chemical substances, such transfer method is very eco-friendly.
Professor Choi said, “As the new graphene transfer method has a wide range of applications and allows a large surface transfer, it will contribute to the commercialization of graphene electronic devices.” He added that “because this technique has a high degree of freedom in transfer process, it has a variety of usages for graphene and 2 dimensional nano-devices.”
This research was sponsored by the Ministry of Science, ICT and Future Planning, the Republic of Korea.
Figure 1. Cover photo of the journal Small which illustrates the research findings
Figure 2. Above view of Graphene layer transferred through the new method
Figure 3. Large surface transfer of Graphene
2015.01.23 View 15677