Slip effect based bimodal nanofibrous membrane for high-efficiency and low-resistance air purification

Nanofiber materials have great potential in air filtration, especially to deal with the micro-/nano-particulate matters (PM). However, there still remains a challenge to reduce pressure drop while maintaining ultra-high filtration efficiency for fibrous membrane filters. In the present article, the high-efficiency and low-resistance bimodal nanofibrous membrane filter based on slip effect was designed and fabricated. By modelling and numerically simulating the air flow field around single fiber, the fiber with diameter of 70 nm was found to be most effective for slip flow to reduce air resistance. To introduce the slip effect into fibrous membrane, bimodal structured fibrous membrane filters which consisted of scaffold fibers (200 nm) and the optimal slip effect functional fibers (70 nm) were designed to increase the gap between the fibers. Furthermore, a sandwich structured fibrous membrane filter was fabricated via one-step free surface electrospinning, in which the bimodal fibers (70 + 200 nm) was in the middle layer, while the upper and lower layers were consisted of unimodal fibers of 110 and 70 nm, separately, to form gradient air passageway. The sandwich structured fibrous membrane presented a filtration efficiency of 99.984% for PM0.26, meeting the requirements of precision filtration under the premise of low-resistance (85.02 Pa), with a QF (quality factor) as high as 0.1028 Pa−1. The results shown in the current work provide an efficient way for the design and fabrication of nanofibrous membrane for high-efficiency and low-resistance air purification against PM.