Electrospun bimodal nanofibrous membranes for high-performance, multifunctional, and light-weight air filtration: A review

Electrospun nanofibrous air-filtration membranes, which are cost-effective materials that help safeguard human health, have garnered widespread attention. To comprehensively enhance the protection capabilities, comfort (for masks), energy efficiency (for air purifiers), and achieve optimal overall benefits, there is a demand for the functionalization and lightweighting of high-performance air filtration membranes. Bimodal nanofiber membranes can deliver high-performance air filtration with a higher proportion of fine fibers, contributing to a lightweight design. Moreover, they are compatible with various functionalization strategies. Therefore, an in-depth analysis of electrospun bimodal nanofibrous membranes is key to promoting the development of high-performance air filters. However, this has yet to be achieved. Importantly, deep-level mechanisms of the electrospun jet behavior are involved in the fabrication of bimodal structures. Reflection on these phenomena may guide theoretical and experimental studies in related fields, such as fluid dynamics and materials science. This study details electrospun bimodal nanofibrous membrane properties, high-performance air filtration mechanisms, fabrication methods, and molding mechanisms. Subsequently, the functionalized applications are summarized. Finally, the challenges encountered in the development of bimodal air filtration membranes are discussed.