MOSCOW, February 25. /TASS /. A research team from the Institute of Theoretical and Experimental Biophysics of the Russian Academy of Sciences and MIPT (Moscow Institute of Physics and Technology) student Andrei Avseenko have synthesized material that is just a perfect filter for protection of respiratory organs, analytical research and other practical purposes.

An almost weightless fabric made of nylon nanofibers with a diameter less than 15 nm beats any other similar materials in terms of filtering and optical properties, MIPT press service said.

The scientists whose work is published in Macromolecular Nanotechnology Journal, characterize their material as lightweight (10-20 mg/m2), almost invisible (95% light transmission: more than that of a window glass), showing low resistance to airflow and efficient interception of <1 micrometer fine particulate matter.

The wording "nanofibers" in the researchers’ article is more than a fashion statement. Previously, the same team demonstrated that reducing fiber diameter from 200 nanometers down to 20 decreased filter resistance to airflow by two thirds, and this effect could no longer be explained by classical aerodynamics. When an obstacle size is smaller than the free path of gas molecules (an average distance one molecule manages to cover before colliding with another), the standard methods estimating aerodynamic resistance based on the continuum theory no longer work. In normal conditions, the mean free path of air molecules makes 65 nanometers.

The scientists used the technique called electrospinning: a jet of a dissolved polymer is ejected through a special nozzle aiming at a target under action of an electric field. From the other side, ethanol is electrosprayed. The polymer jet and the alcohol ions take the opposite electric charges. Colliding in the air, they form ultra-thin fibrous films.