Electrospinning Machine | Synergistic engineering of PEG-modified biomass-based polyester and forsythin for high-efficiency antibacterial air filtration nanofiber membranes

Biomass polyester is a sustainable, low-carbon alternative to petroleum-based polymers. Effective air filtration is crucial for ultrafine particles and pathogens. Although electrospun nanofiber membranes can effectively capture particles, the lack of inherent antibacterial properties poses a contamination risk. This work pioneers dual-functional bio-based polyester nanofiber membranes by adding the single-component Chinese herb extract forsythin, providing both high-efficiency filtration and effective antibacterial activity, thereby advancing sustainable air purification.

Recently, Professor Chen Weichao's team at Qingdao University published their latest research, "Synergistic engineering of PEG-modified biomass-based polyester and forsythin for high-efficiency antibacterial air filtration nanofiber membranes" in the journal Separation and Purification Technology. The researchers developed an antibacterial air filtration nanofiber membrane made from PTF-b-PEG copolyester via electrospinning. By doping PEG into the PTF backbone, the membrane not only improved thermal stability but also exhibited stronger hydrophilicity, excellent flexibility, and uniform morphology. After adding natural forsythin (FT) during electrospinning, the fiber diameter was optimized to 480 nm, achieving 99.92% ultrafine particle filtration efficiency at a low pressure of 72 Pa and a QF of 0.09 Pa⁻¹. Additionally, the membrane inhibited Staphylococcus aureus and Escherichia coli by 98.68% and 99.76%, respectively, with a bacterial interception rate of over 99%, enabling simultaneous interception and killing of bacteria to avoid secondary pollution. This provides a new solution to the functional limitations of traditional filters, highlighting its potential in efficient and sustainable air purification.

Figure 1: Structural characterization and thermal properties of PTF-b-PEG copolyester.

PTF-b-PEG copolyester was synthesized via direct esterification using FDCA, PDO, and PEG as raw materials. Figure 1(a) FT-IR results confirmed the successful incorporation of PEG segments into the PTF backbone. Figure 1(b) shows the TG and DTG curves of PTF-b-PEG copolyester. No significant weight loss was observed before 356.8 °C, indicating that PTF-b-PEG copolyester possesses high thermal stability, ensuring resistance to thermal degradation during processing. Figure 1(c) presents the DSC curve of PTF-b-PEG copolyester. The glass transition temperature (Tg), crystallization temperature (Tc), and melting temperature (Tm) were 51.05 °C, 135.5 °C, and 171.2 °C, respectively.

Figure 2: Morphology and diameter distribution of FTx@PTF-b-PEG nanofiber membranes.

PTF-b-PEG copolyester nanofiber membranes with uniform fiber structure and good morphology were prepared via electrospinning technology. FT was added to the PTF-b-PEG nanofiber membrane. The study found that FT modification significantly reduced the diameter of the nanofibers, indicating its effectiveness in improving the structural performance of the membrane. Figures 2(a)-(d) show the morphology of the FTx@PTF-b-PEG nanofiber membranes. Notably, as the FT content increased, the fiber diameter and diameter distribution gradually decreased. As shown in Figures 2(e)-(h), the average fiber diameter significantly decreased from 1.71 μm to 0.45 μm. The reduction in diameter can be attributed to the addition of FT, which weakened the van der Waals forces and hydrogen bonds between polyester segments, thereby disrupting the entanglement of polymer molecules and reducing the viscosity of the spinning solution. The smaller fiber diameter is bound to enhance the filtration performance of the membrane.

Figure 3: Filtration performance of FTx@PTF-b-PEG nanofiber membranes.

The study concluded through a series of experiments that the FT10@PTF-b-PEG nanofiber membrane with a 10% forsythin (FT) concentration exhibited optimal filtration performance. With a basis weight of 4±0.2 g/m², it achieved a filtration efficiency of 99.92%, a pressure drop of 72 Pa, and a quality factor of 0.09 Pa⁻¹, striking a balance between high-efficiency filtration and low energy consumption. The efficiency remained stable at over 99% under varying airflow velocities and maintained high filtration efficiency over 9 days, demonstrating excellent particle capture capability, dynamic stability, and durability.

Figure 4: Antibacterial performance of FT10@PTF-b-PEG nanofiber membrane.

The study demonstrates that the FT10@PTF-b-PEG nanofiber membrane possesses excellent antibacterial properties. Forsythin (FT) achieved inhibition rates of 98.68% against Staphylococcus aureus and 99.76% against Escherichia coli. The antibacterial mechanism involves the phenolic hydroxyl groups of FT disrupting bacterial cell walls and membranes, while the membrane's hydrophilicity promotes the rapid release of FT, thereby enhancing the antibacterial effect. Concurrently, the addition of FT reduces the diameter of the nanofibers, creating a synergistic effect with its bactericidal activity. The refinement of fibers increases the specific surface area, which not only improves physical interception efficiency but also enhances the contact opportunities between bacteria and FT. Furthermore, the dense structure prolongs the exposure time of bacteria to FT. These two aspects work synergistically to simultaneously enhance both the filtration and antibacterial performance.

Figure 5: Bioaerosol filtration capability of FT10@PTF-b-PEG nanofiber membrane.

The study confirms that the FT10@PTF-b-PEG nanofiber membrane exhibits excellent performance against bioaerosols. Both it and the PTF-b-PEG membrane can efficiently intercept bacteria; however, only the FT10@PTF-b-PEG membrane demonstrates significant antibacterial properties, achieving inhibition rates of 98.88% against Staphylococcus aureus and 99.73% against Escherichia coli. Furthermore, it causes morphological shrinkage and deformation of bacteria on the membrane. This membrane can be applied in settings with bacterial aerosols, such as public transportation and hospitals, to achieve simultaneous air filtration and sterilization.

Paper link: https://doi.org/10.1016/j.seppur.2025.134918