Self-crystal electret poly(lactic acid) nanofibers for high-flow air purification and AI-assisted respiratory diagnosis.

Particulate matters (PMs), one of the major airborne pollutants, continue to seriously threaten human health and the environment. Here, a self-crystal-induced electret enhancement (SCIEE) strategy was developed to promote the in-situ electret effect and polarization properties of electrospun poly(L-lactic acid) (PLLA) nanofibers. The strategy specifically involved the elaborate pre-structuring of stereocomplex crystals (SCs) with uniform dimensions (∼300 nm), which were introduced into PLLA electrospinning solution as the electrets and physical cross-linking points of high density. It enabled direct fabrication of self-crystal electret poly(lactic acid) (SCE-PLA) nanofibrous membranes (NFMs), effective regulation of nanofiber morphology, enhanced generation of electroactive phases (β phases, SCs, and interfacial domains), synergistically contributing to remarkable increase of dielectric constant (2.48), surface potential (4.60 kV) and charge regeneration performance (tribo-output voltage as high as 37.60 V). This permitted multiple improvements in physical interception and electrostatic adsorption of PMs, as exemplified by efficient removal of PM and PM (94.91 % and 99.15 %) with ultralow air resistance (57.2 Pa, 32 L/min), in clear contrast to the pure PLA counterpart (82.66 % and 80.98 %). Given sustainable regeneration of plentiful charges, SCE-PLA NFMs exhibited long-term electret effect and PM removal (92.53 %) even at intensive inhalation and exhalation airflow (120 and 100 L/min). Moreover, the electroactive SCE-PLA NFMs were ready to realize high-accuracy monitoring (99.23 %) of the respiratory patterns. Our SCIEE strategy opens up a promising pathway to fabricate ecofriendly nanofibers featuring superior in-situ electret effect and charge regeneration capability, appealing for air purification and passive monitoring.