Electrospinning solid nanofibers.  where D is the diameter of the fiber and η is the viscosity of the solution at rest (equilibrium). It has also been shown that the fiber diameter is strongly dependent on the applied electric field. Increasing the applied voltage increases its electrostatic voltage and produces a smaller diameter fiber. [7, 21]. According to Huang et al. [22] The further increase in the electric field is a critical value when the electrostatic repulsive force collides with the surface tension and the charged liquid jet emerges from the apex of the Taylor cone. During the process, the solvent evaporates and contributes to the formation of charged polymer fibers.

Electrospinning solid nanofibers

In the case of a molten mass, the jet ejected from the syringe solidifies as it travels through the air. According to the results of the study by Pham et al. [23] the shape of the bed (bottom) depends on the surface tension of the liquid and the intensity of the electric field. If the electric field is high enough, the jets can detach from most smooth surfaces. The solvent in the polymer jet evaporates as the collector filter moves, increasing the surface charge of the jet. This increase in surface charge causes instability of the polymer beam when passing through the electric field [24]. The polymer beam is first split geometrically into two pads, then split further, repeating the process to compensate for this imbalance. Nanofibers/fibers are formed by the action of a rotational force generated by electrostatic force in the continuous splitting of polymer droplets. It is sequentially deposited on the metallic target plate, forming a mat of nanofiber fleece.

Electrospray/electrospinning technology has been used for a long time, although the much less controlled mechanisms by which nanofibers are formed are not yet fully elucidated. Although little theoretical clarity has been provided, numerous studies have been and are being conducted to investigate the mechanism of fiber formation in order to re-control scaffold design. An even fiber structure can only be achieved with optimal operation during the electrospinning process. The structural morphology of nanofibers is influenced by external and internal parameters [16]. In order to produce meaningful nanofibers, in addition to internal parameters such as applied voltage, working distance and conductivity and conductivity of the polymer solution, external parameters such as humidity and temperature should also be optimized. Intrinsic parameters are more important in determining the overall structure of nanofibers.

Three main parameters, namely solution parameters, process parameters and environmental parameters, tend to affect the electrospinning process. These operating parameters largely determine the desired quality of the produced electrospun fibers [25, 26]. In many applications, a fiber with a diameter of 10 to 1000 nm in size and smooth surface morphology is preferred. According to Lu and Ding [25], changing the properties of the solution is difficult because the relationship between one parameter leads to other parameters. In addition, it is very difficult to isolate it as a controllable parameter. Li and Wang [27] studied the electrospinning process and the effects of operational parameters that govern the process and found that these parameters can affect the morphology and diameter of fibers. In their study on the influence of parameters on the nanofiber diameter, Thompson et al. [28] found that the jet radius can affect the production of electrospun fibers (an important finding).

In their study, a number of parameters significantly influenced fiber formation compared to other parameters. For example, the first electrospinning process by Formhals [29] had some technical disadvantages as the spinning and bonding areas were very small, making it not easy to fully dry the fibers after electrospinning. This resulted in a less aggregated network structure [29]. However, 5 years later, Formhals [30], in his pioneering work, changed the distance between the nozzle and collector (collector) to give the electrospun fibers more drying time at a longer distance.