Figure 1.

Structure and composition of materials in different layers of a standard medical face mask and illustrations of key features from four commercial face masks. (a) Schematic assignment of the function of the respective layers in a medical face mask: a combination of a physical barrier and electrostatic absorption against droplets, viruses, bacteria, and aerosols, containing viruses/bacteria. (b) Typical materials used in respective layers. (c) 3D Morphologies of (i) spunbonded nonwoven fabrics and (ii) melt-blown nonwoven fabrics; (iii) 3D structure of a knitted fabric and (iv) schematic of a wet padding process. (d) Comparison of four representative commercial face masks. (i) UNIQLO AIRism face mask consisting of three functional layers, sunscreen layer, particle filtration layer, and skin-friendly layer; (ii) Graphene-coated mask surface is of excellent self-cleaning and photothermal properties; (iii) Bioinspired spider web-like mask filling ZIF-8 around the nanofibers; (iv) Thermal-management nanofiber-based face mask coating with Ag thin layer. Inset pictures in Figure 1d are reprinted from Ref. [53, 61, 67] with permissions from American Chemical Society and Elsevier.