Reproducing Fine Metal Thin Films on Water Surface... New Nano-Printing Technology Developed

A new concept of nano-printing technology has been developed that enables the transfer of complex metal circuits onto three-dimensional surfaces above water. This printing method does not require adhesives and allows for transfer without surface damage, making it highly promising for diverse applications in advanced industries.

Schematic diagram of metal thin film nanostructure floating technology and transfer process in water. KAIST

KAIST announced on June 15 that a research team led by Inkyu Park, Distinguished Professor at the Department of Mechanical Engineering, in collaboration with Senior Researcher Junho Jeong’s team at the Korea Institute of Machinery and Materials (KIMM) and Professor Junsung Ahn’s team at Korea University Sejong Campus, has developed a technology called “Water-Floated Nano-Transfer Printing (WF-nTP).”

WF-nTP enables the transfer and attachment of precision metal thin films (nanostructures) floated on water onto three-dimensional surfaces.

First, the joint research team deposited 20-nanometer-thick metal thin films—such as gold (Au), platinum (Pt), palladium (Pd), and nickel (Ni)—onto a polymer mold. Using plasma, which is an ionized gaseous state of high-energy material, they selectively removed parts of the mold.

When the structure is placed in water, water seeps through the fine gaps, causing the metal thin film to float on the water in its original shape. The metal circuit is then transferred by dipping the desired object under the floating thin film and lifting it out—a process similar to ladling.

As the water dries, capillary forces (the movement of liquid in narrow spaces) press the circuit onto the surface, and intermolecular forces firmly secure it without adhesives. This is the operating principle of WF-nTP.

The joint research team devised this new approach of “floating metal circuits on water” to overcome the limitations of conventional nano-transfer printing (nTP).

nTP requires high heat, pressure, and adhesives (or chemical solvents) when transferring micro-electronic circuits to other surfaces. As a result, it is difficult to apply nTP to materials such as biological tissues and complex curved surfaces that are vulnerable to heat and pressure.

In contrast, the joint research team explained that WF-nTP overcomes these limitations of nTP and can be widely utilized in advanced industries.

(From left) Professor Inkyu Park, Department of Mechanical Engineering, KAIST; Byungho Kang, PhD candidate, Department of Mechanical Engineering, KAIST; Junho Jung, Principal Researcher, Korea Institute of Machinery and Materials; Professor Junseong Ahn, Korea University Sejong Campus. KAIST

The joint research team has successfully transferred circuits onto hydrophobic surfaces—such as lotus leaves, which strongly repel water. By adding a small amount of ethanol to the water to decrease surface tension (the force that causes the surface of a liquid to contract), they overcame the limitations of existing nTP methods.

The greatest advantage of WF-nTP is its ability to retain the exact shape of the nano-pattern while being applicable to a variety of surfaces.

Utilizing this, the research team fabricated surface-enhanced Raman scattering (SERS) sensors—which can detect trace amounts of chemicals with high sensitivity—and attached them to plant leaves and fruit surfaces. Using these sensors, they successfully detected the pesticide thiram on the surfaces of lemons and oranges.

Additionally, they transferred a palladium (Pd) mesh onto highly stretchable thermoplastic polyurethane (TPU) fibers, resulting in the creation of a wearable, high-performance hydrogen gas sensor.

Distinguished Professor Park stated, “WF-nTP overcomes the limitations of conventional nano-transfer printing, making it possible to replicate nano-patterns onto sensitive surfaces such as living plant leaves and skin without the use of adhesives. We expect this technology to be applied in various fields, ranging from smart agriculture, which measures pesticides without damaging crops, to next-generation robotic electronic skin.”

Meanwhile, Byungho Kang, a PhD candidate at the Department of Mechanical Engineering at KAIST, participated as the first author in this research. The results were recently published online in the international academic journal ‘Nature Communications.’

This content was produced with the assistance of AI translation services.