%64%72%6f%70%6c%65%74
-
KAIST Removes 99.9% of Ultrafine Dust Using Nano Water Droplet Technology
<(From Left) Ph.D candidate Sungyoon Woo, Professor Il-Doo Kim, Professor Seung S.Lee, Ph.D candiate Jihwan Chae, Researcher Jiyeon Yu, (Upper Right) Dr. Yujang Cho>
A KAIST research team has drawn attention by developing a new water-based air purification technology that combines “nano water droplets that capture dust” with a “nano sponge structure that autonomously draws up water,” enabling dust removal using nano water droplets without filters, self-supplied water operation, and long-term, quiet, and safe performance.
KAIST (President Kwang Hyung Lee) announced on the December 8 that a joint research team led by Professor Il-Doo Kim of the Department of Materials Science and Engineering and Professor Seung S. Lee of the Department of Mechanical Engineering developed a new water electrospray–based air purification device that rapidly removes ultrafine dust without filters, generates no ozone, and operates with ultra-low power consumption.
The research team confirmed that this device overcomes the limitations of conventional air purifiers by eliminating the need for filter replacement, producing no ozone, and removing even extremely fine ultrafine dust as small as PM0.3 (diameter 0.3 μm), which is about 1/200 the thickness of a human hair, within a short time. In addition, it demonstrated high stability and durability without performance degradation even during long-term use.
This device was created by combining Professor Seung S. Lee’s “ozone-free water electrospray” technology with Professor Il-Doo Kim’s “hygroscopic nanofiber Emitter” technology.
Inside the device are a high-voltage electrode, a nanofiber absorber that autonomously draws up water, and polymer microchannels that transport water via capillary action. Thanks to this structure, a self-pumped configuration is achieved in which water is automatically supplied without a pump, enabling stable long-term water electrospray operation.
Tests conducted by the research team in a 0.1 m3 experimental chamber showed that the device removed 99.9% of various particles in the PM0.3–PM10 range within 20 minutes. In particular, it exhibited outstanding performance by removing 97% of PM0.3 ultrafine dust, which is difficult to eliminate using conventional filter-based air purifiers, within just 5 minutes.
Even after 30 consecutive tests and 50 hours of continuous operation, the device operated stably without performance degradation, and its power consumption was approximately 1.3 W, which is lower than that of a smartphone charger and only about 1/20 that of conventional HEPA (High Efficiency Particulate Air) filter–based air purifiers.
In addition, because there is no filter, there is no pressure loss in airflow and almost no noise is generated.
This technology maintains high-efficiency purification performance while generating no ozone at all, presenting the potential for a next-generation eco-friendly air purification platform.
In particular, with advantages such as elimination of filter replacement costs, ultra-low power operation, and secured long-term stability, it is expected to expand into various fields including indoor environments as well as automotive, cleanroom, portable, and wearable air purification modules.
Commercialization of this technology is currently underway through A2US Co., Ltd., a university spin-off company from Professor Seung S. Lee’s laboratory.
A2US Co., Ltd. won a CES 2025 Innovation Award and plans to launch a portable air purifier product in 2026. The product is equipped not only with fine dust removal using nano water droplets but also with odor removal and pathogen sterilization functions.
<Figure1.Design and Operating Mechanism of a Miniature Air-Purification Device Based on Cone-Jet Water Electrospray Using a Self-Pumping Hygroscopic (PVA–PAA–MMT) Nanofiber Membrane (PPM-NFM) Emitter.>
<Figure 2. (a) Schematic of the Self-Pumping Hygroscopic Nanofiber Membrane (PPM-NFM) Emitter, and (b) Corresponding Photograph and Surface Scanning Microscopy Images.>
This research was conducted with Jihwan Chae (Ph.D. candidate, Department of Mechanical Engineering, KAIST) and Yujang Cho (Ph.D., Department of Materials Science and Engineering, KAIST) as co–first authors, and with Professor Seung S. Lee (Department of Mechanical Engineering) and Professor Il-Doo Kim (Department of Materials Science and Engineering) as corresponding authors. The research results were published on November 14 in the international journal Advanced Functional Materials (AFM), published by Wiley, a world-renowned publisher in materials science and nanotechnology.
※ Paper title: “Self-Pumped Hygroscopic Nanofiber Emitter for Ozone-Free Water Electrospray-Based Air Purification,” DOI: 10.1002/adfm.202523456
This research was supported by the National Research Foundation of Korea, the Ministry of Science and ICT, and the KAIST–MIT Future Energy Frontier Research Center (AI-robotics–based energy materials innovation) program.
2025.12.08 View 3000 -
Success in Measuring Nano Droplets, A New Breakthrough in Hydrogen, Semiconductor, and Battery Research
<(From Left) Ph.D candidate Uichang Jeong, Professor Seungbum Hong>
In hydrogen production catalysts, water droplets must detach easily from the surface to prevent blockage by bubbles, allowing for faster hydrogen generation. In semiconductor manufacturing, the quality of the process is determined by how evenly water or liquid spreads on the surface, or how quickly it dries. However, directly observing how such water or liquid spreads and moves on a surface ('wettability') at the nanoscale has been technically almost impossible until now, forcing researchers to rely mostly on conjecture. KAIST announced on December 2nd that a research team led by Professor Seungbum Hong of the Department of Materials Science and Engineering, in collaboration with Professor Jongwoo Lim's team at Seoul National University, has developed a technology to directly observe nano-sized water droplets in real-time using an Atomic Force Microscope (AFM) and to calculate the contact angle based on the droplet's shape. This research, by enabling the visual confirmation of the actual shape of nano-droplets, allows for the precise analysis of how well water droplets adhere to and detach from a surface. This is expected to be immediately applicable to various advanced technologies where liquid movement determines performance, such as hydrogen production catalysts, fuel cells, batteries, and semiconductor processes. Recently, precise measurement at the nanoscale has become crucial for wettability analysis technology. Traditional methods using large water droplets, several millimeters in size, could distinguish between hydrophilicity (where water spreads easily) and hydrophobicity (where water doesn't spread easily) on the surface. However, at the nanoscale, the droplets are too small to directly observe their shape. The research team successfully induced nano-droplets to form naturally by gently cooling the surface to a temperature where atmospheric water vapor does not freeze. They then observed these droplets using the non-contact mode of the AFM to capture their original shape. Since nano-droplets are sensitive and can be deformed by mere contact with the probe, precise control is essential. Furthermore, when the team applied this technique to the ferroelectric material lithium tantalate, they were the first to confirm a difference in the nano-droplet contact angle depending on the material's electrical direction (polarization). This difference, which was not visible with large droplets, demonstrates that nano-droplets are highly sensitive to the electrical state of the surface. The team then applied this technology to the water electrolysis catalyst used in hydrogen production, observing a single nano-droplet. This result aids in understanding how water reacts on the catalyst surface and can be used to analyze catalyst performance, particularly how well bubbles detach.
<Figure 1. Nanoscale droplet visualization using non-contact mode>
<Figure 2. Single-droplet visualization formed on sub-micron-sized water-splitting catalyst LiFeLDH particles>
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." This research, in which Uichang Jeong, a PhD candidate in the KAIST Department of Materials Science and Engineering, participated as the first author, was published on October 17th in 'ACS Applied Materials and Interfaces', a prestigious journal in the field of new materials and chemical engineering published by the American Chemical Society (ACS).
Paper Title: Nanoscale Visualization and Contact Angle Analysis of Water Droplets on Ferroelectric Materials
DOI: https://doi.org/10.1021/acsami.5c14404
This research was supported by the Ministry of Science and ICT and the National Research Foundation of Korea.
2025.12.03 View 1994 -
Prof. Sang-Ouk Kim Featured on the Cover of Emerging Investigator Special Issue
KAIST Prof. Sang-Ouk Kim of the Department of Materials Science and Engineering was featured on the cover of the Emerging Investigator Special Issue published by Britain"s Royal Society of Chemistry on June 21, university authorities said on Monday (June 22).
The special issue shed spotlight on 18 up-and-coming scientists who have been selected through the recommendation and rigorous screening process of the editorial and advisory boards of the Royal Society of Chemistry. The 18 scientists consist of six from the American continent, 10 from Europe, one from Japan and one from Korea.
The journal introduced Prof. Kim"s paper, titled "Highly entangled carbon nanotube (CNT) scaffolds by self-organized aqueous droplets." Kim explained in the paper that the cellular CNT demonstrated high electrical conductivity and field-emission properties, which is potentially useful for various applications in electronics and energy storage devices.
2009.06.24 View 19395 -
Professor Seong-Ihl Woo Develops New High-Speed Research Method
Professor Seong-Ihl Woo Develops New High-Speed Research Method
Reduce research periods and expenses for thin film materials several ten times
Posted on the online version of Proceedings of National Academy of Sciences of the United States of America (PNAS) on January 9
A team led by Seong-Ihl Woo, a professor of KAIST Department of Chemical & Biomolecular Engineering and the director of the Center for Ultramicrochemical Process Systems, has developed a high-speed research method that can maximize research performances and posted the relevant contents on the online version of Proceedings of National Academy of Sciences of the United States of America (PNAS), a distinguished scientific journal, on January 9, 2007.
Professor Woo’s team has developed a high-speed research method that can fabricate several tens or several thousands of thin films with different compositions (mixing ratio) at the same time and carry out structural analysis and performance evaluation more than ten times faster and accurately, which leads to the shortening of the research processes of thin film materials. This is an epoch-making method that can reduce research periods and expenses several ten times or more, compared to the previous methods.
The qualities of final products of electronic materials, displays, and semi-conductors depend on the features of thin film materials. Averagely, it takes about two weeks or longer to fabricate a functional thin film and analyze and evaluate its performances. In order to fabricate thin film materials in need successfully, more than several thousand times of tests are required.
The existing thin film-fabricating equipment is expensive one demanding high-degree vacuum, such as chemical vapor deposition, sputtering, physical vapor deposition, laser evaporation, and so on. In order to fabricate thin films of various compositions with this equipment, a several million won-worth target (solid-state raw material) and precursors (volatile organic metal compound) pricing several hundreds won per gram are required. Therefore, huge amount of experiment expense is demanded for fabrication of several ten thousands of thin films with various compositions.
Professor Woo’s team has developed ‘combinatorial droplet chemical deposition’ equipment, which does not demand high-degree vacuum and is automated by computers and robots, by using a new high-speed research measure. The equipment is priced at about 1/5 of the existing equipment and easy for maintenance.
This equipment uses cheap reagents, instead of expensive raw materials. Reagents necessary to form required compositions are dissolved in water or proper solvents, and then applied by high frequencies to make several micrometer-scaled droplets (fine liquid droplet). Theses droplets are moved by nitrogen and dropped onto a substrate, which is to be fabricated into a thin film, and then subsequent thermal treatment is applied to the substrate to fabricate a thin film of required composition. At this moment, several tens or several hundreds of thin films with various compositions can be fabricated at the same time by reducing the size of thin film specimens into millimeter scale with the use of shade mask and adjusting vaporization time with masks, the moving speed of which can be adjusted. The expenses for materials necessary for the fabrication of thin films with this equipment amount to several ten thousands won per 100 grams, which is in the range of 1/100 and 1/10 of the previous methods, and the research period can be shortened into one of several tenth.
“If this new method is applied to the development of elements in the fields of core energy, material and health, which have not been discovered by the existing research methods so far, as well as researches in thin film material field, substantial effects will be brought,” said Professor Woo.
‘Combinatorial droplet chemical vaporization’ equipment is pending a domestic patent application and international patent applications at Japan and Germany. This equipment will be produced by order and provided to general researchers.
2007.02.02 View 23584