Airborne particulate matter represents a silent but pervasive threat to our health, infiltrating our homes, workplaces, and public spaces alike. Air filters are often our primary defense against these microscopic pollutants, which include pollen, dust, and smoke.
However, conventional air filters suffer from a fundamental weakness: they rely on extremely weak adhesive forces (van der Waals interactions) to capture particles. These forces are often insufficient to effectively trap and retain fine particles, leading to poor filtration performance and the release of previously captured pollutants. But what if the answer to these issues was quite literally right under our noses?
In a recent study published in Nature , a research team led by Associate Professor Sanghyuk Wooh from Chung-Ang University has developed an effective bioinspired solution. Dubbed the particle-removing oil-coated (PRO) filter, the proposed air filtration system mimics the way mucus-coated nasal hairs trap particles to achieve remarkable performance. Their findings were published online on June 18, 2025.
The team's strategy focused on creating a stable, thin liquid layer on filter media. They engineered filter fibers by grafting tiny polymer brushes onto their surfaces, then sprayed them with a non-volatile oil chemically similar to the brushes. This chemical match helps the oil spread evenly, forming a uniform film that adheres tightly. Unlike previous liquid-coated filters, this design prevents pore clogging, so air flows freely.
Extensive experiments showed that the PRO filter dramatically improves particle capture. It achieved a 10–30% increase in filtration efficiency across various particle sizes—from fine dust to large pollen—without significantly increasing the pressure required to push air through. This is due to the strong capillary forces provided by the thin oil layer, which enhance particle adhesion by orders of magnitudes.
The PRO filter also excels under tough conditions. While conventional filters may lose efficiency or release particles when airflow increases or changes direction, the PRO filter holds particles tightly. This prevents air re-contamination and enables unique applications, including fan-free air filtration in places like outdoor smoking areas or subway tunnels by simply harnessing natural airflow. "This is the first instance of suppressed dust redispersion and a multidirectional filtration strategy proposing a zero-energy filtration system that uses natural wind," highlights Dr. Wooh.
It is also washable and reusable. Its performance is easily restored by reapplying the silicone oil. Its long lifespan reduces plastic waste, making it a more sustainable option.
Real-world field tests conducted in HVAC systems with the help of WISE & YiRop confirmed all these advantages. "The PRO filters showed outstanding performances in real-world HVAC systems compared to conventional filters. Even though more dust was captured by the PRO filter lifespan of the PRO filter was ~two times longer than conventional filter that effectively reduces plastic waste and HVAC operation cost. In addition, it saves ~20 % energy consumption proposing more environmentally friendly and costless air filtration system," remarks Dr. Wooh.
Overall, the PRO filter represents a significant leap forward in our ability to clean the air we breathe, offering an efficient and environmentally friendly solution to a ubiquitous problem.
