Highly air-permeable and dust-holding protective membranes by hierarchical structuring of electroactive poly(lactic...

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.