Assistant Professor Tan Swee Ching (left), Mr. Sai Kishore Ravi (right) and their team from the National University of Singapore's Faculty of Engineering has developed a novel nanofibre solution that creates thin, see-through air filters (held by Mr. Sai) that can remove up to 90 percent of PM2.5 particles and achieve 2.5 times better air flow than conventional air filters. Image credit: National University of SingaporeA research team from the National University of Singapore (NUS) has successfully concocted a novel nanofiber solution that creates thin, see-through air filters that can remove up to 90 percent of PM2.5 particles and achieve high air flow of 2.5 times better than conventional air filters. As an added bonus, this eco-friendly air filter improves natural lighting and visibility while blocking harmful ultraviolet (UV) rays.

Overall, air filters developed using the nanofiber solution are two times better in quality than commercial ones, and are suitable for applications on windows and doors to improve indoor air quality. This air filter also has promising applications in respirators.

The NUS team's air filter is also eco-friendly and easy to produce — simply by applying the novel nanofiber solution onto a non-woven mesh, and leaving it to dry naturally. Using phthalocyanine, a chemical compound commonly used in dyeing, the NUS team engineered organic molecules that could self-organize, similar to the stacking of building blocks, to form nanoparticles and subsequently, nanofibers. These nanofibers, which exist in the form of an organic solution, easily "cling" onto the non-woven mesh when dispersed onto the material.

Currently, according to researchers, most nanofibers used in air filters are energy intensive to produce and require specialized equipment. The research team has developed a simple, quick and cost-effective way of producing high-quality air filters that effectively remove harmful particles and further improve indoor air quality by enhancing air ventilation and reducing harmful UV rays. In the long run, it may even be possible for a DIY kit to be made available commercially for consumers to make air filters at home. The findings of the study were recently published in the online version of scientific journal, Small.

Air-filters are generally gauged by a parameter called quality factor, which is dependent on two sub-factors, namely particle filtration efficiency and air permeability. Currently, while commercial respirators have a high particle filtration efficiency, air permeability is still considerably low, thus resulting in a low quality factor.

The NUS team's novel air filter achieves a quality factor of about two times higher than commercial respirators. It can filter up to 90 percent of hazardous particles that are less than 2.5 microns in size — also known as PM2.5 particles and associated with serious health threats — while maintaining air flow that is 2.5 times better than these respirators, resulting in better breathability. In fact, the particle filtration efficiency can also be further enhanced, depending on the purpose and functionality of the air filter.

According to researchers, high-efficiency air filters often require multiple layers of microfibers or nanofibers, thus limiting their transparency and as such, they are not suitable to be incorporated in doors and windows of buildings. The see-through air filter developed using the team’s approach has promising applications in terms of improving indoor air quality, and could be especially useful for countries experiencing haze or with high pollution levels.

The NUS research team has filed a patent for this invention. Moving forward, the team is looking into adding more functionalities, such as anti-bacterial properties, into the air filter. The team is also planning to work with industry partners to commercialize this technology.