Highly air-permeable and dust-holding protective membranes by hierarchical structuring of electroactive poly(lactic acid) micro- and nanofibers

The application of biodegradable electrospun poly(lactic acid) (PLA) fibrous membranes (FMs) toward respiratory protection has long been dwarfed by the poor electret effect and short service life. Herein, a micro-on-nano (MON) approach was proposed to fabricate highly electroactive dual-scale poly(lactic acid) (DS-PLA) FMs consisting of inner-layer nanofibers (667 nm) and outer-layer microfibers (1.22 µm). Customized Ag-decorated BTO (Ag-BTO) dielectrics were incorporated to improve the electret effect and charge storage stability of DS-PLA FMs, contributing to the improved dielectric constants (1.40), surface potential (11.4 kV), and triboelectric performance (output voltage of 34.2 V at 10 N, 0.5 Hz). The unique hierarchies and profound electrostatic adsorption effect synergistically allowed the DS-PLA FMs to achieve high PM filtration efficiencies (99.10 % for PM_2.5, 90.37 % for PM_0.3, 32 L/min) at a reduced pressure drop (only 58.8 Pa). Furthermore, benefiting from the cascade filtration mechanisms, the DS-PLA FMs demonstrated superior dust holding capacity (9.4 g/m²), which was 3.2 times higher than that of normal PLA. With the assistance of convolutional neural network (CNN), a set of breathing patterns could be recognized with a classification accuracy as high as 96.7 %. This work provides a facile pathway to significantly prolong the service life of electrospun PLA filters for high-performance air filtration and deep learning-assisted respiratory monitoring.