175 / 2024-03-11 10:36:51

Biodegradable Poly(lactic acid) Filters with MOF Nanosheets as Electrets for Long-Term Filtration and Breath Detection

poly(lactic acid), MOF nanosheets, nanofibrous membranes, air filtration, respiratory monitoring

Whereas the wide use of conventional polymeric air filters causes an increasing accumulation of plastic and microplastic pollution. The notion of developing poly(lactic acid) (PLA)-based fibrous membranes for efficient air purification has generated enormous potential but is frequently challenged by the rapid decay of filtration performance due to the intrinsically poor electret properties of PLA. Here, an electroactivity promotion methodology, that is, one-step synthesis and uniform incorporation of high-dielectric ZIF-8 nanosheets (ZIFNSs), was proposed to facilitate in situ polarization and fiber refinement for electrospun PLA membranes. Although presented with ultralow loadings of ZIFNSs (0.77, 1.53 and 2.30 wt %), the significantly decreased nanofiber diameter (below 500 nm), elevated surface potential (approaching 10 kV) and surface activity, and increased proportions of electroactive phases were simultaneously established for the electrospun PLA/ZIFNS membranes. With well-controlled morphological features, the highly electroactive PLA/ZIFNS membranes exhibited exceptional filtration efficiencies of PM_2.5 and PM_0.3 (99.2% and 96.0%, respectively) even at the highest airflow capacity of 85 L/min, in clear contrast to their pure PLA counterpart (only removing 79.3% PM_2.5 and 74.6% PM_0.3). Benefiting from the increased electroactivity and active contact sites, remarkable triboelectric nanogenerator (TENG) performance was demonstrated for the PLA membrane filters, yielding an output voltage of 4.1 V under deep respiratory vibrations, as well as long-term efficient filtration mechanisms (98.5% removal of PM_2.5 for over 360 min). As triggered by physiological activities like speaking, the PLA-based TENG enabled in vivo real-time monitoring with high sensitivity and specificity. The proposed strategy affords significant promotion of electroactivity and TENG performance for PLA membranes, which may motivate development of ecofriendly air filters for respiratory healthcare and real-time monitoring.