Edinburgh Napier University

  The filtration of airborne particulate matter (PM) and aerosols utilizing nonwoven fibrous materials has received significant research concern due to the continuing global pandemics, especially the outbreak of coronavirus disease (COVID-19), and particularly for face masks as a measure of personal protection. Although spun-bond or melt-blown nonwoven fabrics are among the pioneer materials in the development of polymer microfiber-based face masks or air filters on a large scale, relatively new nonwoven manufacturing processes like electrospinning and solution blow spinning (SBS) are gaining momentum among manufacturers of filter membranes. The high filtration performance of nanofiber face masks is due to their high surface area to volume ratio which increases the interaction between the nanofiber and PM and improves the electrostatic charge distribution of electret filters, allowing enhanced capture capability based on electrostatic deposition. Moreover, the small diameter of nanofibrous filters improves the breathability of the face mask by providing the slip effect, which in turn reduces the pressure drop through the membrane. This paper provides a comprehensive review of contemporary advances in nanofiber face masks, detailing the working mechanism involved, reviewing recent experimental studies, and discussing improvements in filtration efficiency for three main nanofibrous air filtration strategies, including mechanical and electrostatic filtration and antimicrobial functionality. Furthermore, prospective research is introduced which considers the synergistic combination effects of the three filtration mechanisms in designing a multifunctional nanofiber structure that can efficiently capture a wide range of PM with higher filtration efficiency and lower drops in pressure. New trends in the antimicrobial activity of smart material-based nanofibrous membranes in the fight against infectious airborne agents are also described.