FIG. 1.

Summary of fabrics comprising masks considered here. (a) Knitted fabrics formed by looping yarn through previous layers (layers colored differently for clarity). (b) Woven fabrics formed by intersecting perpendicular yarns (the “warp” and “weft”). (c) Nonwoven fabrics are formed by entangling fibers through other means, resulting in less ordered arrangements. Scanning electron microscope images of example fabrics in figures (a)–(c) share a scale bar of 100 μm. (d) Geometric properties measured for sample fabric layers, with region of interest marked with a dashed circle (discussed in text). Respirators and surgical masks are comprised of multiple layers, with individual layers plotted separately within this panel. (e) Distribution of fiber diameters in cotton fabric samples, which loosely follow a lognormal distribution. Inset: the 60% cotton 40% polyester t-shirt shows a second peak at larger fiber diameter corresponding to the second material, which can also be modeled as a lognormal (pink dashed).