In order to solve the natural defects of melt blown cloth, the Nanjing Institute of Advanced Materials Research LED by a team of professors of Nanjing University of Science and Technology, combined with Nanjing National Laboratory of Microstructure, gave full play to professional advantages, and developed a new type of filter material-nanofiber filter membrane. And apply it to the production of the cover, and use the technology achievements to carry out the mission of fighting the "epidemic". The fiber pores of the nanofiber membrane are at the level of hundreds of nanometers (1/1000 of the diameter of the hair strand), which is two orders of magnitude smaller than the traditional meltblown cloth. It can intercept PM2.5 purely physically. Under the same filtering efficiency, the thickness of the nanofiber membrane is greater. Thinness brings lower air resistance. In addition, nanofibers do not require electrostatic electret technology, no charge loss, filtration efficiency degradation and other issues, and have a longer storage and service life.