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

Abstract

Despite the great potential in fabrication of biodegradable and eco-friendly air filters by electrospinning poly­(lactic acid) (PLA) membranes, the filtering performance is frequently dwarfed by inadequate physical sieving or electrostatic adsorption mechanisms to capture airborne particulate matters (PMs). Here, using the parallel spinning approach, the unique micro/nanoscale architecture was established by conjugation of neighboring PLA nanofibers, creating bimodal fibers in electrospun PLA membranes for the enhanced slip effect to significantly reduce the air resistance. Moreover, the bone-like nanocrystalline hydroxyapatite bioelectret (HABE) was exploited to enhance the dielectric and polarization properties of electrospun PLA, accompanied by the controlled generation of junctions induced by the microaggregation of HABE (10–30 wt %). The incorporated HABE was supposed to orderly align in the applied E-field and largely promote the charging capability and surface potential, gradually increasing to 7.2 kV from the lowest level of 2.5 kV for pure PLA. This was mainly attributed to HABE-induced orientation of PLA backbone chains and CO dipoles, as well as the interfacial charges trapped at the interphases of HABE–PLA and crystalline region–amorphous PLA. Given the multiple capturing mechanisms, the micro/nanostructured PLA/HABE membranes were characterized by excellent and sustainable filtering performance, e.g., the filtration efficiency of PM0.3 was promoted 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 to 83.75% at the highest level of 85 L/min. It is of interest that the pressure drop was significantly decreased, mainly arising from the slip effect between the ultrafine nanofibers and conjugated microfibers. The proposed combination of the nanostructured electret and the multistructuring strategy offers the function integration of efficient filtration and low resistance that are highly useful to pursue fully biodegradable filters.

Nanopatterned Electroactive Polylactic Acid Nanofibrous MOFilters for Efficient PM0.3 Filtration and Bacterial Inhibition

“…However, after electrospray of ZIF-8 nanocrystals, the pressure drop of relevant membranes was greatly suppressed due to the decrease of the fiber diameter, suggesting that the fiber diameter played a key role in reducing the pressure drop . On the other hand, the air slip effect induced by the protrusions on the surface of the fibers may be another factor for the reduction of air resistance . Under the same airflow velocity, the filtration efficiency of PLA@ZIF-8 NFMs showed an increasing trend with the increase in ZIF-8 loadings in the dispersions.…”

“…Moreover, the utilization of TENG technology to generate electrical charges is another major breakthrough in the area of air purification . In essence, the increase of the dielectric constant can not only achieve high charge density output but also improve the dipole charge storage capacitance . Therefore, to explore the effect of the improvement of the dielectric constant as well as the change in the fiber morphology, we measured the triboelectric output performance of each sample and performed a comparative study.…”

Biodegradable Electroactive Nanofibrous Air Filters for Long-Term Respiratory Healthcare and Self-Powered Monitoring

“…Since the filtration membranes are subjected to stretching during use, it is necessary for the PLA membranes to have proper mechanical properties, including strength, modulus, and toughness. , As revealed by the stress–strain curves in Figure S7a, it is apparent that all PLA FMs displayed similar deformation modes, and the mechanical response upon external deformation of PLA FMs was significantly promoted by our SREA strategy. As shown in Figure S7b,c, the Young’ s modulus and tensile strength of SP4000 gradually increased to 469.5 ± 2.5 and 19.5 ± 0.84 MPa (45 and 107% increase compared with those of SP300), respectively.…”

The Rise of Electroactive Materials in Face Masks for Preventing Virus Infections

“…Compared to synthetic electrets, naturally charged polymers are most promising for long-lasting air filtration, as they can achieve high electrostatic adsorption without recharging and regeneration. − Chitosan is a charged natural polymer with promise for long-lasting air filtration. Chitosan comprises N -acetyl- d -glucosamine and β-(1–4)-linked d -glucosamine with a highly stable distribution of naturally positively charged groups on its backbone. − The ionizable amino and hydroxyl groups of chitosan facilitate the binding of negatively charged particles in the air and can improve the filtration efficiency of chitosan-based filters. − Moreover, the positive charge of chitosan interacts with the envelope proteins of viruses, disrupts viruses’ structure, or interferes with their replication. − For example, Hathout and Kassem suggested that the application of positively charged chitosan or poly- l -lysine fibers in personal protective masks or protective clothing could reduce the viral load by exploiting the electrostatic repulsion between the fibers and SARS-CoV-2 (Figure c) .…”