Multi-level structured polylactic acid electrospun fiber membrane based on green solvents for high-performance air filtration

Particle matter (PM) pollution seriously threatens public health as it can combine with viruses and heavy metals to enter the human body and cause various diseases. Electrospun polymer fiber membranes, especially biodegradable materials such as polylactic acid, have great potential in PM filtration. However, most polylactic acid fiber membranes are imbalanced between filtration efficiency and resistance. Porous and bead-like fibers offer higher filtration efficiency and are expected to address these challenges with their larger specific surface area. Nonetheless, this structure may compromise the mechanical strength of the fiber membrane, thereby affecting the stability of gas purification and separation. Additionally, the significant volatilization of solvents during solution electrospinning can result in environmental concerns. Here, we prepared a double-layer filter with beads and cracks using a green mixed solvent of N, N-dimethylacetamide and dimethyl carbonate. The difference in the volatilization rate of mixed solvents increases the roughness of the membrane surface and enhances the adsorption of PMs. The structural difference between the two layers of membranes enables graded filtration of particles, further reducing pressure drop. Moreover, the entanglement at the interfaces enhances the mechanical properties of the bilayer membrane. It is worth mentioning that the design of the double-layer membrane improves the overall hydrophobicity and has practical application potential.