Washable air filter recharges in sunlight and LED light

Scientists have developed a reusable air filter that can be recharged using sunlight or indoor LED lighting. The technology could provide a lower-maintenance alternative to conventional air filters used to capture pollutants and airborne particles.

The filter maintained 99% of its maximum filtration efficiency after one month of use and 95% during the following two months, according to a study published in the journal Chem. The researchers say the technology could eventually be incorporated into reusable face masks similar to N95 respirators.

The system uses a polypropylene membrane coated with a material that responds to light and heat. This generates a continuous electrostatic charge on the membrane, allowing it to attract and capture airborne particles.

In tests, the researchers exposed the filter to sodium chloride and soot particles measuring around 0.3 micrometers under humidity levels ranging from 20% to 90%. Unlike many conventional electrostatic filters, the system does not require an external power supply.

When the filter becomes saturated, it can be rinsed with water to remove the collected particles. Exposure to light then restores its electrostatic charge. The researchers found that even low-energy indoor LEDs and sunlight under overcast conditions could recharge the filter to achieve filtration performance comparable to N95 and N99 levels.

According to the researchers, the filter can be reused for hundreds of filtration cycles with little maintenance. Prototypes have already been developed for face masks, outdoor screens and biological applications.

The technology is still at the research stage. The team says the cleaning process could be improved, while further research is needed to determine how easily the filters can be manufactured at scale and incorporated into commercial products.