4.Metal collector

The polymer is dissolved in a solvent before electrospinning, and when it is completely dissolved, it forms polymer solution. The polymer fluid is then introduced into the syringe tube for electrospinning. The positive terminal of the DC power supply is connected to the hollow needle [23], and the negative terminal is connected to the metal collector. With the increase of intensity of the electric field, the repulsive electrostatic force overcomes the surface tension, and the charged jet of the fluid is ejected from the tip of the Taylor cone. The discharged polymer jet undergoes an instability and elongation process, which allows the polymer in the jet to become very long and reduces the diameter of the extruded polymer fiber. The solvent that is used to dissolve the polymer evaporates, and the polymer in the jet is dried. The solvent evaporation depends on the distance between the tip and collector, the solution vapor pressure, and the inside chamber temperature. Stable environmental conditions are therefore important in getting good quality nanofibers. The maximum applied voltage for a needle electrospinning setup is normally less than 30 kV and is also highly humidity dependent [24]. Figure 7 illustrates the schematic diagram of the complete electrospinning setup.

Needleless electrospinning presented as an option electrospinning innovation that deliver nanofibers on a substantial scale. Needleless electrospinning is included as electrospinning of nanofibers straightforwardly from an open fluid surface. Many planes are shaped at the same time from the needleless fiber generator (spinneret) without the impact of capillary effect that is regularly connected with needle electrospinning. Since the fly start in needleless electrospinning is a selfcomposed process which happens on a free fluid surface, the spinning process is hard to control. In needleless electrospinning process, many shapes of spinneret

Figure 7. Needle electrospinning.

Year Author Setup Morphology Fiber bundling/

Theron et al. Polyethylene oxide

Yasmin et al. Polyvinylpyrrolidone

Ding et al. PVA and cellulose

Kumar et al. 12 wt% of

A. 2010

B. 2009

C. 2005

D. 2007

E. 2004

F. 2005

G. 2010

235

Tomaszewski et al.

Varesano et al.

Classification of Electrospinning Methods DOI: http://dx.doi.org/10.5772/intechopen.88654

> Varesano et al.

polymer

Ethylene oxide polymer solution was used for nanofiber. Feeding of solution to each nozzle is done at flow rate of about 0.45 g/h

Polyethylene oxide solution was made in water with ratio 93:7. Flow rate of polymer solution form nozzle tip is 1 ml/h

was used to prepare solution for working fluid in this needless setup. The production rate was in the range of 22.5 ml/(cm<sup>2</sup> min) to 22.5 ml/(cm<sup>2</sup> min) per 1 cm<sup>2</sup> of the spinneret plate

and polypyrrole polymers are used in this experiment. Production of 8 spinneret device is 0.1 g/h

acetate (CA) polymers are used with concentration 10%. Throughput (mg/min jet) PVA solution is 1.9, while CA solution is 2.3

PVA was used in this experiment; its concentration was 15 wt%. With elliptic head production is 11 +/ 3 g per min; with concentric head dry nanofiber production is 12+/ 3 g

polyethylene oxide was used in this experiment. With 3 jets, production is 0.3 ml/min; with 7 jets, it is 0.45 ml/min

Figure 8. Needleless electrospinning [33].

have been invented that have different levels of production. Figure 8 illustrates a schematic diagram of the complete needleless electrospinning setup.

One of the problems also created with needle electrospinning method is low production rate that is typically less than 0.3 g/h [25]. With needleless electrospinning method, production of nanofibers is 250 times [26] more than needle electrospinning. Production depends upon the shape of spinneret used in needleless electrospinning. With different shapes of spinnerets, production rates of 2.5–100 g/h can be achieved.

Different needleless setups, like conical wire coil electrospinning spinneret [25], edge-plate electrospinning setup [27], splashing electrospinning setup [28], rotary cone [29], roller electrospinning process [30], cylinder [31], disk [32], and spiral coil electrospinning processes [33], were made for large-scale production of nanofibers. In all these needleless setups, the spinneret shape is different. Due to this variation in spinneret shape, nanofiber production rate and fiber morphology is different.

### 1.2 Production of nanofibers

Based on the jet formation and the way of using the needles, electrospinning methods can be classified as:


#### 1.2.1 Multi-jet electrospinning methods

In this electrospinning method, multi-jets were used for nanofiber formation. Production of nanofiber increased as compared to needle spinning. Due to multijets, uniform web of nanofiber is not formed; this is due to repletion effect between jets. Some multi-jet electrospinning methods are given in Table 1.

#### 1.2.2 Multi-needle electrospinning methods

In multi-needle electrospinning method, a number of needles are used as spinnerets that contain one or different types of polymer solutions. High voltage is

## Classification of Electrospinning Methods DOI: http://dx.doi.org/10.5772/intechopen.88654


have been invented that have different levels of production. Figure 8 illustrates a

One of the problems also created with needle electrospinning method is low

Different needleless setups, like conical wire coil electrospinning spinneret [25], edge-plate electrospinning setup [27], splashing electrospinning setup [28], rotary cone [29], roller electrospinning process [30], cylinder [31], disk [32], and spiral coil electrospinning processes [33], were made for large-scale production of nanofibers. In all these needleless setups, the spinneret shape is different. Due to this variation in spinneret shape, nanofiber production rate and fiber morphology is different.

Based on the jet formation and the way of using the needles, electrospinning

In this electrospinning method, multi-jets were used for nanofiber formation. Production of nanofiber increased as compared to needle spinning. Due to multijets, uniform web of nanofiber is not formed; this is due to repletion effect between

In multi-needle electrospinning method, a number of needles are used as spinnerets that contain one or different types of polymer solutions. High voltage is

jets. Some multi-jet electrospinning methods are given in Table 1.

electrospinning method, production of nanofibers is 250 times [26] more than needle electrospinning. Production depends upon the shape of spinneret used in needleless electrospinning. With different shapes of spinnerets, production rates of

schematic diagram of the complete needleless electrospinning setup.

production rate that is typically less than 0.3 g/h [25]. With needleless

2.5–100 g/h can be achieved.

Needleless electrospinning [33].

Nanorods and Nanocomposites

Figure 8.

1.2 Production of nanofibers

methods can be classified as:

• Multi-jet electrospinning methods

• Multi-needle electrospinning methods

• Needleless electrospinning methods

1.2.1 Multi-jet electrospinning methods

1.2.2 Multi-needle electrospinning methods

234

A. In this multi-jet electrospinning setup, a pilot plan was used that consist of spinning head. On this spinning head, nine plastic nozzles are deposited in two rows; each nozzle's internal diameter was 0.43 mm. These nozzles are 2 cm away from each other. The polymer solution was provided to the nozzles at spinning head at 0.2 bar; flow rate of solution was about 0.45 g/h. Nanofibers were collected on the nonwoven substrate. Nanofibers were collected that form nine spots on collector, uniform web not formed [34].

B. High-voltage power supply is attached in multi-jet setup; solution is filled in the tube that ejects downward by gravity flow at the rate of 1 ml/h from plastic tip that have orifice diameter of 750 mm. Tests demonstrated that the disparity angles between polymer jets can be lessened by utilizing an auxiliary electrode. Jets used in this setup are 2–16 that have different arrangements [1].

C. This work portrays the consequences of the test examination and modeling of multi-jet amid the electrospinning of polymer solution. The outcomes exhibit how the outside electric fields and shared electric collaboration of various charged jets impact their way and advancement among electrospinning. In this multi-jet electrospinning setup, nine syringes were arranged, and polymer solution was placed identical in all syringes. When electric field is applied to syringes, nanofibers were produced that collected on metal collector. It is observed that nanofibers are collected at nine spots that show repletion effect in multi-jet electrospinning process [35].

D. This setup was the same as conventional needle electrospinning, only microfluidic device was used instead of syringes. The polymer solution was constantly fed through the microfluidic gadget utilizing a syringe pump. High voltage 10–15 kV was applied with spinning distance of 10 cm. It was shown that the morphology and measurement of the nanofibers can be altered by modifying the polymer focus, surface strain, salt, quality of the potential, and nourish rate [36].

E. In this multi-jet electrospinning setup, polymers (PVA and cellulose acetate (CA)) were physically blended with each other. This setup contained four syringes placed on the setup which moved along the track. Distance between the tips of syringes was 3 cm and rotating collector was used. The speed of the rotatable tubular layer and the mobile stand can be controlled by PC. The PVA and CA arrangements were set in various syringes as indicated by the necessity. The consistent nanofiber mats were gathered on the surface of foil and dried at 80°C in vacuum for 24 h [37].

F. The electrospinning testing done with three sorts of electrospinning heads, series, elliptic, and concentric, demonstrated that the last two enabled the procedure to continue on the premise of minimal multi-jet frameworks utilizing at least 10 turning channels. The concentric electrospinning head, which turned out best as to both the effectiveness and the nature of the procedure, can deliver 1 mg of dry PVA nanofibers from one turning channel amid 1 min [38].

G. The attention was on investigating the fiber repulsion in multi-jet electrospinning. The utilization of multi-jet was hazardous because of fiber repulsion. In this multi-jet setup, a novel spinneret was used to make nanofiber, and increment in the yield has been illustrated. A plastic channel plan with numerous pores exhibited decreased fiber repulsion. This novel plastic channel setup yielded strands with more steady and smaller diameter fibers than with multi-needle electrospinning [39].

#### Table 1.

Multi-jet electrospinning methods.

applied to the tip of the needle and nanofibers are deposited on collector. The main advantage of multi-needle electrospinning is we can mix different polymers at our required ratio (Table 2).

#### 1.2.3 Classification of electrospinning methods

It may be defined as the method in which fiber jets are produced or generated from the free surface of liquid. It can also be defined as the technique of producing the fibers from open liquid surface. Based on the fiber generating method, the motion of spinneret, and collection direction of fibers, the needleless electrospinning techniques can be classified as:

1.2.3.1 Free surface spinning method

encompassing needles in the needle arrangement [41].

and more uniform nanofibers [42].

Multi-needle electrospinning methods.

Table 2.

237

In bubble spinning method, air is supplied from porous surface that is placed at the bottom of polymer solution. Bubble is made at the surface of polymer solution, and

A. In this multi-needle electrospinning setup, three syringes were used that contain different polymers. Conveyor belt was used as collector. During electrospinning three types of fibers were mixed together very easily. During electrospinning repletion,

B. Three needles were used in this setup that are mounted vertically. Polymer solution was pumped through syringes at rate of 0.1 ml/min. The point of this paper is to research the electric field bending in various needles by utilizing limited component investigation and to decide its consequences for the electrospinning procedure. It can be presumed that as the quantity of needles in the course of action expands, the electric field at the tip of each needle diminishes essentially because of the impact of the

C. In this multi-needle electrospinning setup, three needles were used, which are arranged in triangle. An auxiliary plate anode has been utilized to be associated with a three-needle framework to get a more uniform electric field. This electrospinning investigations and electric field reenactment exhibit that the multi-needle spinneret with an auxiliary plate can deliver better

polymer jets were observed that could be reduced by increasing distance between needle jets [40].

Year Author Setup Morphology Fiber bundling/

Wang et al. Polystyrene,

polymer

Aldrich polyethylene oxide was employed for preparation of solution; concentration of solution was 5% by weight. The solution was forced through syringe pump at the rate of 0.1 ml/

min

Polyoxyethylene solution concentration 7 wt % was used for experiments. All experiments were carried out at 22 kV voltage, 22 cm collecting distance, and 0.3 ml/h solution flow rate per needle

polyvinylidene fluoride, and polyacrylonitrile solutions are used in this setup with concentrations of 4, 21, and 12% by weight, respectively

1.2.3.1.1 Bubble spinning methods

A. 2014

B. 2011

C. 2012 Angammana et al.

Classification of Electrospinning Methods DOI: http://dx.doi.org/10.5772/intechopen.88654

> Sheng Xie et al.

## Classification of Electrospinning Methods DOI: http://dx.doi.org/10.5772/intechopen.88654

A. In this multi-needle electrospinning setup, three syringes were used that contain different polymers. Conveyor belt was used as collector. During electrospinning three types of fibers were mixed together very easily. During electrospinning repletion, polymer jets were observed that could be reduced by increasing distance between needle jets [40].

B. Three needles were used in this setup that are mounted vertically. Polymer solution was pumped through syringes at rate of 0.1 ml/min. The point of this paper is to research the electric field bending in various needles by utilizing limited component investigation and to decide its consequences for the electrospinning procedure. It can be presumed that as the quantity of needles in the course of action expands, the electric field at the tip of each needle diminishes essentially because of the impact of the encompassing needles in the needle arrangement [41].

C. In this multi-needle electrospinning setup, three needles were used, which are arranged in triangle. An auxiliary plate anode has been utilized to be associated with a three-needle framework to get a more uniform electric field. This electrospinning investigations and electric field reenactment exhibit that the multi-needle spinneret with an auxiliary plate can deliver better and more uniform nanofibers [42].

#### Table 2.

applied to the tip of the needle and nanofibers are deposited on collector. The main advantage of multi-needle electrospinning is we can mix different polymers at our

A. In this multi-jet electrospinning setup, a pilot plan was used that consist of spinning head. On this spinning head, nine plastic nozzles are deposited in two rows; each nozzle's internal diameter was 0.43 mm. These nozzles are 2 cm away from each other. The polymer solution was provided to the nozzles at spinning head at 0.2 bar; flow rate of solution was about 0.45 g/h. Nanofibers were collected on the nonwoven substrate.

B. High-voltage power supply is attached in multi-jet setup; solution is filled in the tube that ejects downward by gravity flow at the rate of 1 ml/h from plastic tip that have orifice diameter of 750 mm. Tests demonstrated that the disparity angles between polymer jets can be lessened by

C. This work portrays the consequences of the test examination and modeling of multi-jet amid the electrospinning of polymer solution. The outcomes exhibit how the outside electric fields and shared electric collaboration of various charged jets impact their way and advancement among electrospinning. In this multi-jet electrospinning setup, nine syringes were arranged, and polymer solution was placed identical in all syringes. When electric field is applied to syringes, nanofibers were produced that collected on metal collector. It is observed that nanofibers

D. This setup was the same as conventional needle electrospinning, only microfluidic device was used instead of syringes. The polymer solution was constantly fed through the microfluidic gadget utilizing a syringe pump. High voltage 10–15 kV was applied with spinning distance of 10 cm. It was shown that the morphology and measurement of the nanofibers can be altered by modifying the polymer focus, surface strain,

E. In this multi-jet electrospinning setup, polymers (PVA and cellulose acetate (CA)) were physically blended with each other. This setup contained four syringes placed on the setup which moved along the track. Distance between the tips of syringes was 3 cm and rotating collector was used. The speed of the rotatable tubular layer and the mobile stand can be controlled by PC. The PVA and CA arrangements were set in various syringes as indicated by the necessity. The consistent nanofiber mats were gathered on the surface of foil and dried at 80°C in vacuum

F. The electrospinning testing done with three sorts of electrospinning heads, series, elliptic, and concentric, demonstrated that the last two enabled the procedure to continue on the premise of minimal multi-jet frameworks utilizing at least 10 turning channels. The concentric electrospinning head, which turned out best as to both the effectiveness and the nature of the procedure, can deliver 1 mg of dry PVA

G. The attention was on investigating the fiber repulsion in multi-jet electrospinning. The utilization of multi-jet was hazardous because of fiber repulsion. In this multi-jet setup, a novel spinneret was used to make nanofiber, and increment in the yield has been illustrated. A plastic channel plan with numerous pores exhibited decreased fiber repulsion. This novel plastic channel setup yielded strands with more steady and

Nanofibers were collected that form nine spots on collector, uniform web not formed [34].

utilizing an auxiliary electrode. Jets used in this setup are 2–16 that have different arrangements [1].

are collected at nine spots that show repletion effect in multi-jet electrospinning process [35].

It may be defined as the method in which fiber jets are produced or generated from the free surface of liquid. It can also be defined as the technique of producing the fibers from open liquid surface. Based on the fiber generating method, the

motion of spinneret, and collection direction of fibers, the needleless

required ratio (Table 2).

Multi-jet electrospinning methods.

salt, quality of the potential, and nourish rate [36].

Nanorods and Nanocomposites

nanofibers from one turning channel amid 1 min [38].

smaller diameter fibers than with multi-needle electrospinning [39].

for 24 h [37].

Table 1.

236

1.2.3 Classification of electrospinning methods

electrospinning techniques can be classified as:

Multi-needle electrospinning methods.

## 1.2.3.1 Free surface spinning method
