KAIST Develops Filter-Free Air Purifier Using Nano Water Droplets

Researchers at Korea Advanced Institute of Science and Technology (KAIST) have developed a new water-based air purifier technology that removes dust using nano water droplets without filters by combining a technology that captures dust with nano water droplets and a nano sponge structure that draws water on its own.

KAIST announced Wednesday that a joint research team led by Professor Kim Il-doo of the Department of Materials Science and Engineering and Professor Lee Seung-seop of the Department of Mechanical Engineering has developed a new water electrostatic spray-based air purification device that rapidly removes ultrafine dust without filters, produces no ozone, and operates on ultra-low power.

The research team confirmed that the device can overcome the limitations of conventional air purifiers by removing ultrafine particles smaller than PM0.3 (0.3 micrometers in diameter, about 1/200th the thickness of a human hair) in a short time without requiring filter replacement and without generating ozone. The team also demonstrated high stability and durability with no performance degradation even after prolonged use.

The device was created by combining Professor Lee's "ozone-free water electrospray" technology with Professor Kim's "hygroscopic nanofiber" technology.

Inside the device are high-voltage electrodes, a nanofiber absorber that draws water on its own, and polymer microchannels that move water through capillary action. This structure enables a self-pumped mechanism that automatically supplies water without a pump, allowing stable water electrospray over extended periods.

In tests conducted in a 0.1 cubic meter experimental chamber, the device removed 99.9% of various particles ranging from PM0.3 to PM10 within 20 minutes. It showed particularly outstanding performance by removing 97% of PM0.3 ultrafine particles within five minutes, which are difficult to remove with conventional filter-type air purifiers.

The device operated stably without performance degradation through 30 consecutive tests and 50 hours of continuous operation. Power consumption was approximately 1.3 watts, less than a smartphone charger and about one-twentieth that of conventional HEPA (High Efficiency Particulate Air) filter-based air purifiers.

Additionally, without filters, 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 possibilities as a next-generation eco-friendly air purification platform.

The technology is expected to expand into various fields including vehicle air purifiers, clean rooms, portable devices, and wearable air purification modules, in addition to indoor environments, through advantages such as eliminating filter replacement costs, ultra-low power operation, and long-term stability.

Commercialization of this technology is underway through A2US, a startup founded from Professor Lee's laboratory.

A2US won a CES 2025 Innovation Award and plans to launch a portable air purifier product in 2026. The product will feature not only fine dust removal using only nano water droplets but also odor removal and pathogen sterilization functions.

The research was conducted with Chae Ji-hwan, a doctoral student in KAIST's Department of Mechanical Engineering, and Dr. Cho Yu-jang from KAIST's Department of Materials Science and Engineering as co-first authors. Professor Lee Seung-seop (Department of Mechanical Engineering) and Professor Kim Il-doo (Department of Materials Science and Engineering) participated as corresponding authors.

The research findings were published on November 14 in Advanced Functional Materials (AFM), an international academic journal by Wiley, a globally recognized authority in materials science and nanotechnology.