Antimicrobial Nanofiber Based Filters for High Filtration Efficiency Respirators

Electrospinning has been used to develop and upscale polyacrylonitrile (PAN) nanofibers as effective aerosol filtration materials for their potential use in respirators. The fibers were deposited onto non-woven spunbond polypropylene (SPP) and the basis weight (grammage, g/m²) was varied to assess the resulting effect on filtration efficiency and breathing resistance of the materials. The results indicated that a basis weight in excess of 0.4 g/m² of PAN electrospun fibers yielded a filtration efficiency over 97%, with breathing resistance values that increased proportionally with the amount of basis weight added. With the aim of retaining filter efficiency whilst lowering breathing resistance, the basis weight of 0.4 g/m² and 0.8 g/m² of PAN electrospun fibers were strategically split up and stacked with SPP in different configurations. The results suggested that a symmetric structure based on SPP/PAN/PAN/SPP was the optimal structure, as it reduces SPP consumption while maintaining an FFP2-type of filtration efficiency, while reducing breathing resistance, specially at high air flow rates, such as those mimicking FFP2 exhalation conditions. The incorporation of zinc oxide (ZnO) nanoparticles within the electrospun nanofibers in the form of nanocomposites, retained the high filtration characteristics of the unfilled filter, while exhibiting a strong bactericidal capacity, even after short contact times. This study demonstrates the potential of using the symmetric splitting of the PAN nanofibers layer as a somewhat more efficient configuration in the design of filters for respirators.