Bioelectrets in Electrospun Bimodal Poly(lactic acid) Fibers: Realization of Multiple Mechanisms for Efficient and Long-Term Filtration of Fine PMs

Despitethe great potential in fabrication of biodegradable andeco-friendly air filters by electrospinning poly-(lactic acid) (PLA)membranes, the filtering performance is frequently dwarfed by inadequatephysical sieving or electrostatic adsorption mechanisms to captureairborne particulate matters (PMs). Here, using the parallel spinningapproach, the unique micro/nanoscale architecture was establishedby conjugation of neighboring PLA nanofibers, creating bimodal fibersin electrospun PLA membranes for the enhanced slip effect to significantlyreduce the air resistance. Moreover, the bone-like nanocrystallinehydroxyapatite bioelectret (HABE) was exploited to enhance the dielectricand polarization properties of electrospun PLA, accompanied by thecontrolled generation of junctions induced by the microaggregationof HABE (10-30 wt %). The incorporated HABE was supposed toorderly align in the applied E-field and largely promote the chargingcapability and surface potential, gradually increasing to 7.2 kV fromthe lowest level of 2.5 kV for pure PLA. This was mainly attributedto HABE-induced orientation of PLA backbone chains and C Odipoles, as well as the interfacial charges trapped at the interphasesof HABE-PLA and crystalline region-amorphous PLA. Giventhe multiple capturing mechanisms, the micro/nanostructured PLA/HABEmembranes were characterized by excellent and sustainable filteringperformance, e.g., the filtration efficiency of PM0.3 waspromoted from 59.38% for pure PLA to 94.38% after addition of 30 wt% HABE at a moderate airflow capacity of 32 L/min and from 30.78 to83.75% at the highest level of 85 L/min. It is of interest that thepressure drop was significantly decreased, mainly arising from theslip effect between the ultrafine nanofibers and conjugated microfibers.The proposed combination of the nanostructured electret and the multistructuringstrategy offers the function integration of efficient filtration andlow resistance that are highly useful to pursue fully biodegradablefilters.

Automated summary

By using the parallel spinning approach, a micro/nanoscale architecture was created in electrospun PLA membranes, resulting in bimodal fibers that reduce air resistance. The addition of bone-like nanocrystalline hydroxyapatite bioelectret (HABE) enhanced the dielectric and polarization properties of the membranes, leading to improved filtration efficiency. The combination of the nanostructured electret and multistructuring strategy allows for efficient filtration and low resistance, making them highly useful for fully biodegradable filters.