Chinese researchers have created a new type of air filter that can be powered by sunlight, according to a study published in the journal Chem. The filter was developed by scientists at Jilin University and uses a special coating on a polypropylene membrane. This coating contains materials that react to light and heat to create an electric charge on the filter’s surface. This charge helps attract and trap tiny particles from the air, such as dust, pollutants, and even viruses, without the need for electricity. The filter maintained 99% of its filtering ability after one month of use and 95% after two additional months. Researchers believe this technology could eventually be used in reusable N95 masks, which could be cleaned and recharged using sunlight or a lamp instead of being discarded once they lose effectiveness. However, the technology is still in the early stages of development and not yet ready for widespread use. Most current air purifiers and masks rely on electricity or disposable filters that need frequent replacement. Many commercial filters use a method called corona discharge, which applies a high voltage to give particles a static charge so they can be captured. These systems require an external power source. Another alternative, known as triboelectric filtration, uses static electricity from friction but often loses effectiveness over time, especially in humid conditions. The new coating developed by the Chinese team combines a material called PVDF-TrFE, which can hold an electric charge, with tiny particles of a liquid metal that convert light into heat. This heat activates the charge-holding properties of the material, making the filter more effective and stable. To test the filter’s performance, researchers exposed it to particles like salt and soot, each about 0.3 micrometers in size, under different humidity levels. They found that even low-energy light sources, such as indoor LED lights or sunlight on a cloudy day, were enough to generate the necessary charge for the filter to achieve filtration efficiency comparable to N95 and N99 masks. In comparison, standard N95 masks lost their effectiveness over time, especially at humidity levels between 20% and 60%, with their filtration efficiency dropping below 95%. The researchers also tested versions of the filter coated with silver and copper. The copper-coated filter was able to capture and neutralize 99.99% of the common human coronavirus HCoV-OC43, while the silver-coated version showed strong antibacterial properties. The filter was also more effective at trapping spores from the fungus Aspergillus niger compared to standard filters. Testing suggested that the small amounts of metal released during use were not high enough to pose a safety risk. Scientists have already made prototypes that integrate the filter into face masks, outdoor window screens, and tools for collecting biological samples. When used in outdoor screens, the filter maintained high transparency while capturing more large airborne particles than commercial screens. Researchers say the system offers a sustainable and adaptable solution to common issues like clogging and poor filtration stability in traditional filters. While the self-cleaning process still needs improvement, the team plans to explore how to mass-produce the filter and apply it to various products. They also aim to develop air purification methods for extreme environments in the future.