An air filter that uses sunlight and indoor LED lights to charge has the potential to make face masks and air purifiers more efficient, longer lasting, lower maintenance, and less expensive, according to a new study published last month in Chem. 

Many conventional filters use an electrical charge to help attract airborne particles from the air for purification. But that charge gradually dissipates and accumulated particles eventually clog the filtration material, “resulting in short service life and recurring costs,” write the researchers.

For the study, a team led by researchers from Jilin University in Changchun, China, coated a polypropylene membrane with materials that convert light into heat to generate a continuous surface charge that captures airborne particles while allowing air to pass through. 

The filter achieved 99% filtration efficiency for a month without increased airflow resistance. Efficiency remained at 95% over the next two months, with only a slight increase in resistance.

When particles accumulate, the filter can simply be rinsed with water and exposed to light to restore its charge. Even low-energy indoor LED light and sunlight on overcast days provided enough energy to recharge the material to filter at N95- and N99-level efficiency, according to a Cell Press news release. 

Light-charged filters provide ‘a novel pathway to enrich applicability, such as indoor air purification, epidemic disease prevention, and personal hygiene protection.’

The study highlights the filter’s potential for real-world applications, say the researchers, who developed prototypes for face masks, outdoor screens, and biological equipment. But, they add, some aspects of the filter could be further improved, and more research will be needed to assess the possibility of mass production and integration with other products. 

Yet, they conclude, a light-charged filter “provides a novel pathway to enrich applicability, such as indoor air purification, epidemic disease prevention, and personal hygiene protection.”