Nanoweb for Nanobugs: Nanofiber Filter Media for Face Masks

Abstract

Nonwoven face masks are being explored as potential multifunctional, wearable, and smart healthcare devices. The fibers in the nonwoven layers can effectively mechanically and electrostatically capture submicrometer particles depending on their fiber size, porosity, and surface charge. While surface charge enhances the filtration of mechanical capture alone, charge is sensitive to moisture, heat, disinfectant solvents, and storage. TriboElectric NanoGenerators (TENG) are a solution to leverage the biomechanical action of respiration to generate a skin-safe level of charge to maintain the electrostatic capture mechanism throughout the wear cycle. In this study, hexadimethrine bromide (PB) and poly(methyl vinyl ether-alt-maleic anhydride) (PMA) were mixed with poly(vinyl alcohol) (PVA) and electrospun into hybrid PVA nanofibers to compare their filtration performance to pure PVA nanofibers. Fiber and pore size were measured from scanning electron microscopy (SEM) images, fiber chemistry was characterized via Fourier Transform InfraRed (FTIR) spectroscopy, TENG performance was measured via output voltage, static and dynamic breathability were measured via Air Permeability (AP) and in-line differential pressure (dP), respectively, and filtration efficiency (FE) was calculated from penetrated particle count during a simulated breathing experiment. Optimized for fiber and pore size distributions, PVA fibers achieved 92.3% FE of 0.3 μm particles and dP of 53.8 cm water, PVA/PB fibers achieved 92.5% FE and 18.3 cm water, and PVA/PMA fibers achieved 88.0% and 66.1 cm water. Output voltage was found to be dependent on moisture content, with the pure PVA nanofibers generating the highest positive voltage when wet, PVA/PMA nanofibers generating a less positive voltage, and PVA/PB generating a negative voltage. The combination of filtration and TENG performance positions both the pure and hybrid PVA nanofibers for incorporation into a face mask as multifunctional nanofiber layers. The hybrid PVA nanofibers specifically can be further tested as selective capture membranes toward controlled adhesion, on-mask sample collection/preparation, pathogen detection, and health data monitoring.