MEXICO: Researchers have turned a material used in surgical gloves into a low-cost, highly efficient air filter that could be used to improve face masks and scrub the exhaust from power plants
in the past few years, Yi Cui, an associate professor of materials science and engineering at Stanford, has made several business trips to China.
Each time he has found himself choked by smog produced by automobiles and coal power plants.
After a few of these trips, he came up with an idea to clean the pollution and set to work designing an inexpensive, efficient air filter that could ease the breathing for people in polluted cities with his students.
“My lab group really likes to solve problems, even if it’s something we’ve never worked on,” Cui said. “We think we could use this material for personal masks, window shades and maybe automobiles and industrial waste. It works really well, and it might be a game-changer.”
The work is published in the journal Nature Communications.
This was the first time Cui’s group had designed an air filter – Cui’s work with nanomaterials focuses primarily on battery technology – so he and his students didn’t immediately look to materials that have traditionally been used in air filters.
Instead, they looked for polymers that would have a strong attraction to the main components of smog, particularly particle matters that are smaller than 2.5 microns, known as PM2.5. These pose the greatest risk to the human respiratory system and overall health; current filtration systems that can remove them from the air are very energy-intensive.
It turned out that polyacrylonitrile (PAN), a material used to make surgical gloves, met these requirements.
“It was mostly by luck, but we found that PAN had the characteristics we were looking for, and it is breathtakingly strong,” said Po-Chun Hsu, co-author and a student in Cui’s lab.
Using a technique called electrospinning, the researchers converted liquid PAN into spider-web-like fibers that are just a thousandth the diameter of a human hair. In the study, the researchers approximated Beijing’s smog by flowing smoke from burning incense over different densities of the fiber, and later performed a field test in Beijing. The final material allows about 70 per cent transparency and yet collects 99 per cent of the particles.
