Electrospinning Equipment: Electrospun Janus Composite Fiber Membrane and its Separation and Antibacterial Properties

A Janus membrane is a membrane material with an asymmetric structure or composition, and its two sides exhibit completely different wettabilities. This unique property endows Janus membranes with extensive application potential in fields such as directional fluid transportation, sensors, and oil - water separation. With the development of nanotechnology, the electrospinning technique has become an important method for preparing Janus membranes. The electrospinning technique can efficiently prepare nanofibers. By controlling the size, shape, and doping characteristics of the fibers through an electrospinning device, high permeability and functionality of the membrane material can be achieved. Polyvinylidene fluoride (PVDF), due to its strong hydrophobicity, is often used as the hydrophobic layer of Janus membranes; while polyacrylonitrile (PAN), because of its strong hydrophilicity, is frequently used as the hydrophilic layer of Janus membranes. In addition, to impart antibacterial properties to the membrane material, N - halamine antibacterial agents are often added in research. These compounds can effectively destroy bacterial proteins by releasing oxidizing halogen positive ions, thus achieving a broad - spectrum antibacterial effect.

The research team led by Li Zhiguang from the School of Textile Science and Engineering at Jiangnan University published the latest research results titled "Composite Fiber Membrane with Janus Structure via Electrospinning Technique and its Separation and Antibacterial Properties" in the journal Fibers and Polymers. The team successfully prepared a PVDF@MC/PAN@MC composite fiber membrane with a Janus structure through the electrospinning technique. This achievement provides new ideas and methods for the application of Janus membranes in the fields of separation and antibacterial, and offers important references for the development of high - performance separation membranes.

The team first mixed polyvinylidene fluoride (PVDF) with the N - halamine antibacterial agent MC, and used DMF and acetone as mixed solvents to prepare the hydrophobic layer (PVDF@MC fiber membrane) through an electrospinning machine. Subsequently, polyacrylonitrile (PAN) was mixed with the N - halamine antibacterial agent MC, and DMF was used as the solvent to prepare the hydrophilic layer (PAN@MC fiber membrane) through an electrospinning device. Finally, the two - layer fiber membranes were combined by continuous electrospinning to form a composite fiber membrane with a Janus structure. The top layer of this membrane is hydrophobic and underwater oleophilic, while the bottom layer is hydrophilic and underwater oleophobic. (See Figures 1 and 2)

Figure 1 Preparation process of PVDF@MC/PAN@MC composite fiber membrane

Figure 2 SEM images (A), average diameters, and porosities (B) of the fiber membranes. a PVDF fiber membrane; b PAN fiber membrane; c the top layer of the PVDF@MC/PAN@MC composite fiber membrane; d the bottom surface of the PVDF@MC/PAN@MC composite fiber membrane

Compared with the PVDF fiber membrane, the water contact angle of the top layer increased from 130.0° to 132.6°. When an oil droplet contacts the surface of the top layer of the PVDF@MC/PAN@MC composite fiber membrane immersed in deionized water, the oil droplet spreads rapidly. Compared with the PAN fiber membrane, the underwater oil contact angle of the bottom layer of the PVDF@MC/PAN@MC composite fiber membrane increased from 124.6° to 143.0°. (See Figure 3)

Figure 3 Water contact angles (WCAs) and underwater oil contact angles (UWOCAs) of the fiber membranes. a The spreading process of water droplets on the surface of the PAN fiber membrane; b the spreading process of water droplets on the surface of the PAN@MC fiber membrane; c the WCA of the PVDF fiber membrane; d the WCA of the PVDF@MC fiber membrane; e the UWOCA of the PAN fiber membrane; f the UWOCA of the PAN@MC fiber membrane

Through the pure - water flux experiment, the research team measured the water fluxes of different fiber membranes. The experimental results showed that the pure - water flux of the PVDF fiber membrane was 62 L•m⁻²•h⁻¹, that of the PAN fiber membrane was 1110 L•m⁻²•h⁻¹, and that of the PVDF@MC/PAN@MC composite fiber membrane was 91 L•m⁻²•h⁻¹. This indicates that the pure - water flux of the composite fiber membrane is between that of the PVDF and PAN fiber membranes. (See Figure 4)

Figure 4 Pure - water fluxes of the fiber membranes. a PVDF fiber membrane; b PAN fiber membrane; c PVDF@MC/PAN@MC composite fiber membrane

Through separation experiments with mud, toluene emulsion, CuSO₄ solution, and MB solution, the research team verified the separation performance of the composite fiber membrane. The experimental results showed that the separation efficiency of the PVDF@MC/PAN@MC composite fiber membrane for mud was 98.58%, for toluene emulsion was 30.58%, and for CuSO₄ and MB solutions were 35.85% and 60.78% respectively (See Figure 5). These results indicate that the separation efficiency of the composite fiber membrane is higher than that of PVDF and PAN fiber membranes, while the separation flux is between the two, reflecting the comprehensive influence of its double - layer structure on the separation performance.

Figure 5 Separation efficiencies and fluxes of the fiber membranes. a PVDF fiber membrane; b PAN fiber membrane; c PVDF@MC/PAN@MC composite fiber membrane

Compared with PVDF and PAN fiber membranes, the antibacterial performance of the PVDF@MC/PAN@MC composite fiber membrane has been significantly improved. However, due to the low content of the N - halamine antibacterial agent MC, it cannot achieve rapid sterilization in a short time. The top and bottom layers can only completely kill bacteria after 30 minutes of contact with Staphylococcus aureus and Escherichia coli (See Figure 6).

Figure 6 The antibacterial performances of the fiber membranes against Staphylococcus aureus (S. aureus) (A) and Escherichia coli (E. coli) (B), and the bacterial reduction rates of the fiber membranes against S. aureus (C) and E. coli (D) (The inoculum population of S. aureus was 6.80 × 10⁶ CFU/swatch; the inoculum population of E. coli was 6.32 × 10⁶ CFU/swatch). S1. S. aureus exposed to the PVDF fiber membrane for 30 minutes; S2. S. aureus exposed to the PAN fiber membrane for 30 minutes; S3. S. aureus exposed to the top layer of the PVDF@MC/PAN@MC composite fiber membrane for 1, 5, 10, and 30 minutes; S4. S. aureus exposed to the bottom layer of the PVDF@MC/PAN@MC composite fiber membrane for 1, 5, 10, and 30 minutes; E1. E. coli exposed to the PVDF fiber membrane for 30 minutes; E2. E. coli exposed to the PAN fiber membrane for 30 minutes; E3. E. coli exposed to the top layer of the PVDF@MC/PAN@MC composite fiber membrane for 1, 5, 10, and 30 minutes; E4. E. coli exposed to the bottom layer of the PVDF@MC/PAN@MC composite fiber membrane for 1, 5, 10, and 30 minutes. a PVDF fiber membrane; b PAN fiber membrane; c the top layer of the PVDF@MC/PAN@MC composite fiber membrane; d the bottom surface of the PVDF@MC/PAN@MC composite fiber membrane

This research successfully prepared a PVDF@MC/PAN@MC composite fiber membrane with a Janus structure through the electrospinning technique, providing new ideas for the development of high - performance separation membranes. This membrane not only performs well in separation performance, showing high - efficiency separation of mud, oil - water emulsions, metal ions, and organic dyes, but also has antibacterial properties. This achievement promotes the application of Janus membranes in the fields of separation and antibacterial, and also provides important theoretical and experimental bases for the development of multifunctional composite fiber membranes.

Article source: https://doi.org/10.1007/s12221-025-00862-y