Sandwich-structured bimodal fiber/bead-on-string fiber composite membrane for comfortable PM0.3 filter

Particulate matter (PM) pollution causes critical harm to human health and global environment. However, the protective respirators attain high-performance filtration of the most permeable PM0.3 by tight stacking of fibers and seriously compromising their wearing comfort. Herein, a fluffy sandwich-structured membrane (SSM) composed of bimodal fibrous layers and bead-on-string fibrous layer is designed to endow the air filter with both high-performance filtration and superior thermal-wet comfort. Based on the electrospinning technique, the bimodal fibers made of nano-/submicron-fibers (about 46 nm and 155 nm) are formed by inducing the jet splitting while the bead-on-string fibers consisting of submicron-fibers (≈ 120 nm) and micro-beads (≈ 3.37 μm) are prepared through manipulating the Rayleigh instability of jets. Due to the structural design of small pores and low packing density, the SSM exhibits excellent PM0.3 removal of 99.8%, low filtration resistance of 65 Pa, and high quality factor of 0.097 Pa-1. It also shows long-term filtration stability and durability under high humidity conditions. Moreover, the SSM simultaneously possesses superior thermal-wet comfort of heat dissipation, air permeability of 164 mm·s-1, and water vapor transmission of 7.6 kg·m-2·d-1. This work may offer a novel insight for exploiting high-performance and comfortable personal protective materials.