KAIST develops nano-printing technique to attach ultrafine metal circuits to plants, electronic skin

South Korean researchers have developed a nano-printing technique that can transfer ultrafine circuits onto virtually any surface, with potential applications in smart farming, wearable healthcare and robotic electronic skin.

KAIST announced Monday that a team led by Park In-kyu, a chair professor in the Department of Mechanical Engineering, jointly developed a "water-surface floating nano-transfer printing" technology with a team from the Korea Institute of Machinery and Materials led by Dr. Jeong Jun-ho and a team from Korea University led by Professor Ahn Jun-sung. The technique floats precision metal thin films on water and transfers them intact onto a wide range of three-dimensional surfaces.

Conventional nano-transfer printing used in fabricating electronic devices and sensors requires high heat and pressure, strong adhesives or chemical solvents — making it difficult to apply to biological tissue or complex curved surfaces sensitive to such conditions.

The research team deposited extremely thin layers of metals — including gold (Au), platinum (Pt), palladium (Pd) and nickel (Ni) — onto a polymer mold, then selectively removed parts of the mold using plasma, an ionized high-energy gas. When placed in water, water seeps through microscopic gaps, causing a 20-nanometer-thick metal film to detach and float to the surface while retaining its original shape.

The team transferred the metal circuit using a "scooping" method — submerging the target object beneath the floating film and slowly lifting it out. As the water evaporates, capillary forces draw the circuit tightly against the surface. Once the water is fully gone, intermolecular attraction locks it firmly in place without any adhesive.

The team also successfully transferred circuits onto hydrophobic surfaces — those that strongly repel water, such as lotus leaves. Adding a small amount of ethanol to the water reduced surface tension and allowed the researchers to overcome a key limitation of existing techniques.

In smart farming, electrodes attached directly to crop leaves could serve as agricultural IoT sensors for real-time monitoring of a plant's moisture levels, nutritional status and growth signals. The technology could also function as surface-enhanced Raman scattering (SERS) sensors for on-site, non-destructive testing of pesticide residues on leaves or fruit without picking them.

In wearable healthcare, thin films transferred onto stretchable fabric could be used to create smart clothing in everyday garment form, skin-adhesive patches for electrocardiogram and body-temperature monitoring, and hydrogen-leak detection garments for industrial settings.

In medicine and biotech, the technology could be applied to biocompatible medical devices such as electronic skin transferred directly onto the body and post-surgical rehabilitation monitoring patches.

"This technology is significant because it goes beyond the substrate limitations of conventional nano-transfer printing, enabling nano-pattern transfer onto sensitive surfaces like living plant leaves or skin without adhesives or heat," Park said. "It will be possible to expand into the biotech domain — applying electrical stimulation to cells, monitoring growth states and tracking drug delivery responses at the cellular level."

The findings were published in the international journal Nature Communications.