Electrospun bilayer nanomembrane with hierarchical placement of bead-on-string and fibers for low resistance respiratory air filtration

High pressure drop (air resistance) and bulky structure are the main challenges to address for a respirator filter. An electrospun nanofiber membrane (ENM) is an effective filter media which can be a solution to reduce the filter pressure drop and bulkiness. This paper investigated bilayer, beaded ENMs to prepare efficient lightweight respiratory filter media with less pressure drop. The focus is on producing a continuous bead on string nanostructure at small basis weight levels (0.5–2 g m−2). The filtration performance of the single and bilayer beaded ENMs was measured against particles of size 0.3–5 µm. The surface morphology of the ENMs was investigated using field emission scanning electron microscopy and capillary flow porometry. The thickness of ENM was measured by a contactless method using 3D laser scanning digital microscope. The presence of beads changed the thickness, packing density and pore characteristics of the ENMs consequently their filtration performance. Bilayer, beaded ENMs with specific stacking at 0.5 g m−2 showed better performance than the commercial P2 type respirator.