Synergistic dual-scale engineering of PA6 nanofibrous membranes with PS microspheres: Gradient assembly for high-efficiency, low-resistance air filtration

This study presents a dual‑scale engineering strategy combining microscale fiber modulation with gradient assembly to overcome the efficiency‑resistance trade‑off in air filters. PA6/PS composite membranes were fabricated via solution blow spinning by embedding three different diameters of PS microspheres into PA6 nanofibers. Larger microspheres induced fiber refinement and a unique “smaller‑pore, higher‑porosity” microstructure, reducing pressure drop while enhancing filtration efficiency. Assembling these tailored layers into a large‑to‑small pore gradient (LMS PA6/PS gradient membrane) enabled sequential coarse‑to‑fine filtration. The optimized membrane achieved higher filtration efficiency (99.98 ± 0.016%) and lower pressure drop (130 ± 1 Pa), delivered a quality factor of 0.067 Pa −1 , which is superior to the homogeneous membrane and N95–8210 respirator, and had an excellent moisture vapor transmission rate of 4715.19 ± 132.45 g/(m 2 ·24 h). Moreover, the LMS membrane showed the slower pressure drop increase during continuous loading compared with 3 M N95–8210, confirming its size‑classified capture mechanism and extended service life. From an integrated pollution control perspective, the prolonged service life reduces material waste, and the spent membrane can be recycled via solvent-based recovery methods, avoiding secondary pollution from direct incineration, offering a viable solution for reducing personal exposure to hazardous particulate matter.