New window screens with pollutant-trapping nanofibers may allow residents of smog-choked cities to breathe easier. The fibers are made of nitrogen-containing polymers and are sprayed onto screens in a technique called blow-spinning, in which a stream of air stretches out droplets of polymer solution in midspray to form an extremely thin layer of nanofibers.

Scientists at Stanford University and at Tsinghua University in Beijing recently reported in Nano Letters that they have developed a variety of blow-spun polymers (materials commonly used in rubber gloves and tents) capable of filtering more than 90 percent of the hazardous, lung-penetrating particulate matter that typically passes through standard window screens. The pollutant-absorbing nanofibers were sprayed onto rolling flexible nylon mesh at a rate of almost one meter per minute. Researchers also deposited the fibers onto metal-coated mesh and wiped off the film with tissues after heavy absorption.

In a 12-hour field test on a window in Beijing under severely hazy air conditions, a window screen coated with the so-called polyacrylonitrile nanofibers filtered out 90 percent of harmful particulate matter, which can cause lung cancer and heart disease. Now that's a breath of fresh air.