Researchers have developed an air filter that can be charged by sunlight or indoor LED lights, an experimental technology that could be used in air purifiers and in reusable versions of masks with filtration capacity similar to N95 and N99.
The system uses a polypropylene membrane coated with a material that responds to light and heat, continuously generating an electrostatic charge on the surface. This charge allows capturing particles present in the air without the need for an external power source.
Conventional air filters often use a high-voltage electric field, known as corona discharge, to impart electric charge to particles in the air and facilitate their retention by the filter. Although effective, this method requires an external power source. Other alternatives, such as triboelectric filters, have limitations related to the materials used and the gradual loss of electric charge.
To test the new system, the researchers exposed the filter to sodium chloride and soot particles about 0.3 micrometers in size, under humidity conditions ranging from 20% to 90%.
The results indicate that the filter maintained 99% of its maximum filtration efficiency after one month of use and 95% during the following two months. Even low-intensity light sources, such as indoor LED lights or sunlight on cloudy days, were sufficient to restore the electrostatic charge needed to achieve filtration levels equivalent to those of N95 and N99 classes.
Another feature of the system is its reusability. When the filter becomes saturated with particles, it can be washed with water. Then, exposure to light allows the surface electrostatic field to be recovered. According to the researchers, this process could enable hundreds of filtration cycles with reduced maintenance requirements.
The team has already developed prototypes intended for facial masks, outdoor-use barriers, and biological equipment. In the case of masks, the technology could be integrated into reusable models similar to N95s, which were widely used during the COVID-19 pandemic.
Despite the initial results, the technology remains in the experimental stage. The researchers acknowledge that the self-cleaning process can be improved and that further studies will be needed to determine whether the system can be produced at scale and integrated efficiently into other products.
The study was published in the scientific journal Chem, from Cell Press.
