| Dec 03, 2025 |
Nano droplets reveal how water behaves on high-tech surfaces
Scientists used Atomic Force Microscopy to watch nano droplets in real time, exposing how water interacts with surfaces and improving energy and semiconductor technologies.
(Nanowerk News) Water droplets that cling to surfaces can slow hydrogen production by trapping gas bubbles. Droplets that spread unevenly across a semiconductor wafer can compromise device performance. In many cutting-edge industries, how liquids behave on a surface determines how well the process works. Yet seeing that behavior at the nanoscale has been almost impossible, leaving scientists to make educated guesses rather than examine what is actually happening.
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KAIST reported that a team led by Professor Seungbum Hong in the Department of Materials Science and Engineering, working with Professor Jongwoo Lim’s group at Seoul National University, has developed a way to watch nano sized water droplets in real time. Using an Atomic Force Microscope (AFM), the researchers captured the droplets as they formed and used their shapes to calculate the contact angle, a key measure of how well droplets stick or detach from a surface.
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The findings are published in ACS Applied Materials & Interfaces ("Nanoscale Visualization and Contact Angle Analysis of Water Droplets on Ferroelectric Materials")
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| Single-droplet visualization formed on sub-micron-sized water-splitting catalyst LiFeLDH particles. (Image: KAIST)
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The advance lets scientists visually confirm how nano droplets behave, enabling precise analysis of adhesion and detachment. The approach is expected to have immediate use in hydrogen production catalysts, fuel cells, batteries, and semiconductor manufacturing, where liquid motion directly affects performance.
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Measuring wettability usually involves millimeter sized droplets. These larger drops can show whether a surface is hydrophilic or hydrophobic, but they reveal nothing about how liquids behave at the nanoscale. Small droplets are too tiny to observe clearly, and even the light touch of a probe can distort them.
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The team overcame that challenge by gently cooling a surface until atmospheric water vapor condensed into stable nano droplets without freezing. They then used the AFM in non contact mode to record the droplets’ natural shapes. Because nano droplets are extremely sensitive, maintaining precise control was essential.
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When the researchers applied the method to the ferroelectric material lithium tantalate, they became the first to show that nano droplet contact angles change depending on the material’s electrical direction. This difference cannot be seen with larger droplets and reveals that nano droplets respond strongly to a surface’s electrical state.
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The team also tested the technology on a water electrolysis catalyst for hydrogen production, tracking the behavior of a single nano droplet. The observation helps explain how water interacts with the catalyst surface and provides clues about bubble detachment, a critical factor in catalyst performance.
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Professor Seungbum Hong stated, “This research is an important case demonstrating that the Atomic Force Microscope can be used to directly visualize nano-sized water droplets and even measure the contact angle. Being able to observe the behavior of water droplets in the nano-world, which was previously invisible, will establish this as a core analysis technology for the development of next-generation energy and electronic materials.”
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