Bead-on-String-Like Nanofibrous Membrane for High-Efficiency, Low-Pressure Drop Air Filters with Antimicrobial Properties

Particulate matter (PM) pollution poses a significant risk to public health, as it can carry pathogens such as bacteria and viruses into the body through the respiratory tract, leading to a variety of illnesses. Electrospun nanofibrous membranes (ENMs) exhibit substantial promise for air filtration applications. However, most nanofibrous membranes have a trade-off between filtration efficiency and pressure drop. The bead-on-string structured membranes are characterized by their ability to achieve a higher efficiency and lower pressure drop. Here, we prepared a bead-on-string-like structure of ENM with fluxible poly(p-phenylene terephthalamide) (f-PPTA) and silver nanoparticles (Ag NPs) on a polypropylene (PP) nonwoven fabric substrate. The two layers of membranes enable graded filtration and reduce the pressure drop. The f-PPTA plays a role in controlling both the diameter and roughness of nanofibrous membranes, and its grafted quaternary ammonium salts impart antimicrobial properties to the membrane. Ag NPs serve as a skeleton and form a bead-on-string-like structure with f-PPTA/PA6 nanofibers. In conclusion, this membrane achieves a 99.39% efficiency for PM0.3, a low-pressure drop of 21 Pa, and a quality factor (QF) value of 0.24 Pa–1 and exhibits antibacterial properties against both E. coli and S. aureus. This study indicates that the nanofiber structure can be transformed into a bead-on-string-like structure with low-pressure drop by reasonable matching of the size of nanoparticles and nanofibers, and the combined action of f-PPTA and Ag NPs can effectively improve the antibacterial effect of nanofiber membranes, which is of significant importance for the research on high-efficiency particulate air (HEPA) filter.