When a smog alert is declared, citizens are often told to stay indoors, but that dirty air is still going to get in. However, people in affected cities could soon breath easier thanks to a new nanofiber solution developed at the National University of Singapore (NUS). Air filters made from the material can block most small particles, while still letting air circulate, and at the same time block UV rays without reducing natural light.

To develop the new material, the NUS team first created organic molecules out of a chemical compound called phthalocyanine. These molecules organized themselves into a nanofiber structure, and when the solution is spread over a non-woven mesh, the fibers cling to the material and form thin, clear sheets once they're allowed to dry out. The relatively easy manufacturing technique should also keep the costs and energy footprint down.

Air filters made with the nanofiber material were found to block up to 90 percent of particles smaller than 2.5 microns, a category known as PM2.5 that are thought to be the most hazardous to human health. Depending on the use case for a given air filter, the creators says there's still room for their recipe to be tweaked to make that efficiency even better – which could help it catch up to other systems that boast 99 percent efficiency in filtering out PM2.5 particles.

While it's busy blocking particles, the new filters are also apparently much better at letting air pass through. According to the team, a respirator made using the new material could boast air permeability that is up to 2.5 times better than existing products.

"Air pollution poses serious health threats," says Tan Swee Ching, lead researcher on the study. "Therefore, there is a strong need for economical and effective technologies for air filtration. Currently, most nanofibers used in air filters are energy intensive to produce and require specialized equipment. Our team has developed a simple, quick and cost-effective way of producing high-quality air filters that effectively remove harmful particles and further improves indoor air quality by enhancing air ventilation and reducing harmful UV rays."

Since the material is transparent, the researchers say it could be handy for fitting filters into windows and doors, so residents could crack a window to let in a breeze while still keeping the big city smog out. The system is just as selective when it comes to light, flooding a room with natural light, but keeping harmful UV rays at bay.

"High-efficiency air filters often requires 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," says Tan. "The see-through air filter developed using our 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. While increasing filtration efficiency will lead to a trade-off in air flow, the overall performance of our air filter is still better than commercial respirators."

The next step for the team is to add anti-bacterial functions to the filter's repertoire, and look at ways to commercialize the technology, for which they've already filed a patent.

The study was published in the journal Small and the researchers describe their work in the video below.

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