Highly Efficient and Sustainable PM Filtration Using Piezo Nanofibrous Membrane with Gradient Shrinking Porous Network

Nanofibrous filters have limited filtration against ultrafine airborne particulate matter (PM) due to thick fiber fineness and large pore size, which can be unraveled by increasing thickness and basis weight, however, the pressure drop of the filters also increases sharply. Inspired by the bryophyte leaf structure, unconventional piezo nanofibrous membranes with gradient shrinking porous network are created for PM filtration by one-step electrospinning of polyvinylidene fluoride (PVDF), dibenzylidene sorbitol (DBS), and short-chain fluorinated alkyl modified silica (F-SiO2) through pattern metallic mesh collectors. The membranes are assembled into charged and hydrophobized gradient porous networks with pores in feeding to outlet gradually shrinking. This structure features a well-designed filtration mechanism that balances filtration efficiency and pressure drop, facilitating high trap efficiency against PM (PM0.3 > 98.82%; PM0.5 > 99.87%, quality factor ∼ 0.121–0.507 Pa−1; PM0.8–7.5 = 100%) with a low pressure drop (16–55 Pa) and good stability in an acid, alkali, ultraviolet (UV), or humid environment. Simultaneously the piezo nature of the membrane endows renewable surface charge richness by hand pressing to provide sustainable caption of ultrafine particles, especially PM0.3. This study provides a new design approach for constructing PM filters in a reliable, sustainable and affordable way.