Electrospinner: Review of wet electrospinning to prepare functional fibers: rich morphology and great power

Background

Wet electrospinning is an important branch of traditional electrospinning. Wet electrospinning replaces the traditional solid collector with a liquid coagulation bath, which can produce fibers with porous, curved and twisted structures and prepare continuous nanofiber yarns. In addition, the surface of wet electrospinning fibers can be modified and functionalized, which greatly improves the performance of electrospun fibers in various applications and promotes the industrial production of electrospun fibers in the textile field.

Recently, Zheng Jie/Long Yunze from Qingdao University and Chen Zhigang from Donghua University published a review article entitled "Advances in Wet Electrospinning: Rich Morphology and Promising Applications" in Advanced Fiber Materials. The basic principles of wet electrospinning technology, the improvement and evolution of the device, and its potential in preparing nanofibers with rich morphology are introduced. The research progress and development prospects of wet electrospinning are summarized from different application fields.

The main point of this paper

First, the difference between wet electrospinning and traditional electrospinning is introduced. From the perspective of fiber formation, traditional electrospinning is to stretch the polymer solution into fibers with diameters ranging from micrometers to nanometers under a high-voltage electrostatic field, as shown in Figure 1a. In contrast, wet electrospinning technology is to squeeze the polymer solution into a thin stream, which is then coagulated into fibers in a coagulation bath (Figure 1b). This method is controllable during the fiber forming process, so it has unique advantages in preparing ordered fibers and specific functional short fibers.

Secondly, the principle of wet electrospinning technology is introduced. Wet electrospinning mainly includes an injection propulsion device, a high-voltage power supply, and a coagulation bath collection device, as shown in Figure 2. The wet electrospinning process generally includes four consecutive stages: (1) charge excitation; (2) jet linear propagation; (3) coil jet dynamics; (4) coagulation. During the coagulation process, a chemical reaction occurs between the polymer and the coagulant, and the solvent diffuses from the raw material solution to the coagulation bath, resulting in a double diffusion effect, thereby accelerating the formation of ultrafine fibers. The coagulation bath is the key to the unique advantages of wet electrospinning over traditional electrospinning in terms of fiber morphology, surface modification and functionalization, and yarn preparation. Coagulation bath devices usually include plate, drum, vortex, and disc collection.

Then, the potential of wet electrospinning in the preparation of patterned fibers is summarized. The coagulation bath in the wet electrospinning process is beneficial to the transformation of the fiber from liquid to solid. This allows for better control of the coagulation rate of the spinning solution and the phase separation process inside the fiber. The increase in the concentration of the coagulation bath improves the uniformity of fiber coagulation and reduces the formation of macropores, thereby reducing the porosity of the native fiber. These characteristics can be used to design and manufacture patterned fibers for biomedical or industrial devices, such as core-sheath fibers for drug delivery, highly porous fibers, beaded fibers, or adhesive films.

Finally, the advantages, current challenges, and future developments of wet electrospinning are summarized. Advantages of wet electrospinning technology: (1) Adjustable fiber diameter; (2) Diverse materials and strong scalability; (3) Controllable fiber structure; (4) Wide application. However, the rapid development of wet electrospinning technology has also exposed some problems, making its industrial development face challenges: (1) Low industrial production efficiency; (2) Insufficient control of fiber morphology and microstructure, limited performance; (3) Complex equipment operation and high cost; (4) Solvent recovery and environmental pollution.

summary

In view of the shortcomings of wet electrospinning, the development of this technology in the future should focus on the following aspects:

(1) Equipment optimization. The purpose is to improve and optimize the wet electrospinning device to adapt to more materials, including changing the structure and shape of the spinneret to adjust the diameter and shape of the fiber.

(2) Optimizing the spinning solution. By optimizing the formula of the spinning solution, the quality and yield of the fiber can be improved.

(3) Microfluidic fiber spinning chemistry. The structure and properties of the fiber can be changed by adjusting the chemical composition of the spinning solution, and chemical reactions can be introduced during the spinning process.

(4) Automation and intelligence. With the development of automation and intelligence technology, wet electrospinning equipment is expected to gradually achieve automation and intelligent control.