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What is Electrospinning?
Electrospinning is one of the processes of manufacturing nanofibers, and it is a technology that uses an electric field to make liquid or solid materials into fibers.
This process involves spraying a liquid or solid material placed in an electric field from the electrode. In electrospinning, a voltage is applied between the electrode and the object to form an electric field.
At this time, a liquid or solid material increases in the form of a fiber along the flow of current from the electrode by the electric field between the electrode and the object. The fiber is sprayed from the electrode and falls vertically, during which the material dries rapidly in the air to form solid fibers.
Electrospinning is used in numerous applications. It can be applied in various fields such as filtering devices, medical materials, parts of electronic devices, fiber reinforcement, and energy storage devices, utilizing the characteristics of nanofibers.
With nanofibers’ unique fine diameter and excellent surface area, they can give them a variety of functional properties and provide solutions suitable for specific applications.
Electrospinning is known as a simple and economical manufacturing process, and it is possible to manufacture various materials and forms of fibers. Through this, the development of nanofiber technology and its application in various applications are becoming possible.
Components of Electrospinning
Power supply
The electrospinning process uses an adjustable high-voltage power supply to initiate the spinning process.
In order to collect the electrospun fibers, the collector is usually grounded and pulled into a specific area. At this time, grounding the collector works well with thin thickness, but the fibers may gather in a disadvantageous position.
Therefore, it is advantageous to apply a negative voltage to the collector to improve fiber collection. This action maximizes the emitter-collector electric potential difference, thereby improving the fiber yield during the electrospinning process.
Collectors
The electrospun fibers can be collected using various collectors after solidification. These collectors can significantly influence the final design of the electrospun samples.
Fixed collectors are usually made up of flat plates that can be adjusted to the desired limits, so they are used to collect fibers in random directions. This is suitable for collecting random fibers. Alternatively, the electrodes of the collector can be arranged in parallel so that the nanofibers are aligned. This helps collect the nanofibers in the desired pattern or arrangement.
Rotation collectors include disks, mandrels, and drums. These collectors have various dimensions. Mandrels are composed of short diameters, which collect fibers in random directions. On the other hand, disks and drums can collect highly aligned structures if they have a sufficiently high diameter/length ratio and rotational speed. These collectors allow for the elongation of the fibers and provide a greater linear speed to help maintain a high degree of alignment.
In addition, to obtain a large amount of fiber web through continuous collection, a conveyor-type or roll-to-roll collector can be constructed. This allows efficient collection of fibers.
Solution supply systems
The two systems mainly used to supply polymer solutions in electrospinning processes are syringe pump systems and pressurized liquid supply systems.
1. Syringe Pump System : Simple to use in the laboratory, the syringe pump system is a structure that fills the syringe with a solution and quantitatively pushes the plunger to supply the solution. The system can adjust the flow rate from 0.01ul/min to 100ml/h by adjusting the capacity of the syringe and the operating speed of the pump. In addition, it can be used in various ways, such as arranging multiple syringes and supplying them to multiple nozzles at the same time.
2. Pressurized Liquid Supply System : A pressurized liquid supply system is a method of supplying a solution under pressure. The system uses a high pressure pump or pressure control device to hold a solution at a fixed pressure, which supplies the solution. Pressurized liquid supply systems are mainly used when a large volume of solution needs to be supplied, and are applicable to commercialized industrial equipment.
Of these two systems, the syringe pump system is a relatively easy way to use in the laboratory, providing precise solution supply and a variety of adjustment options. The syringe pump system can be flexibly utilized for a variety of applications and experimental needs.
Nozzles
Electrospinning nozzles are used in needle-based electrospinning technology with various configurations. These nozzles can consist of single, concentric, and multi-axis phase nozzles.
1. Single Nozzle : A single nozzle flows a liquid from the nozzle, which forms a single structure of fiber. This is the most basic method of producing fibers using a single solution.
2. Concentric nozzle : In concentric nozzle, fibers can be developed as core-shell structures or as split structures. This is the method of producing fibers using multiple solutions, in which the core-shell structure forms fibers by surrounding the core solution in the center and placing the shell solution on the outside. Split structure is how multiple solutions are formed apart within a fiber. In addition, Janus fibers (fibers with Janus structures) can be developed.
3. Multiaxial phase nozzles : Multiaxial phase nozzles can be used to produce fibers that can discharge more than one solution at a time. This method supplies multiple solutions to a nozzle composed of islands type to form various fibers.
A typical electrospinning head consists of a single capillary needle, but multiple needles may be implemented in the body of the spinneret to increase the throughput of the electrospinning fiber. This increases the production rate and fiber yield, as all nozzles are fed from the same solution supply. This allows for the efficient production of more fibers.
Various polymer types
One of the main benefits of electrospinning technology is that it can handle a wide variety of materials. The technology can be used to mix or suspension polymers, additives, and many other types of materials well in a solution. In this way, different types of materials are utilized in the electrospinning process, producing different results.
Polymers used in electrospinning are mainly classified into three types: natural, synthetic, and semi-synthetic polymers. Each of these polymers is classified according to the properties of the raw materials and is used in various fields depending on their characteristics and uses.
1.natural polymer
•First, natural polymers are polymers extracted from natural resources and have the main characteristics of biocompatibility and biodegradability. Natural polymers such as gelatin and collagen are widely used in medical fields, especially in tissue engineering, etc. Since they are obtained from nature, they are highly biocompatible as they can be safely broken down in vivo.
2.synthetic polymer
•Second, synthetic polymers are artificially created polymers that are designed and developed to meet specific application requirements. Polycaprolactone, nylon 6, and others are examples of such synthetic polymers, which have the advantage of being inexpensive and easy to control the properties of the polymer, such as mechanical properties, decomposition speed, and melting point.
3.semi-synthetic polymer
•Finally, semi-synthetic polymers are polymers that are based on natural polymers but have changed their chemical structure through specific chemical treatments. Cellulose acetate is an example of such a semi-synthetic polymer, a polymer derived from cellulose through reaction with acetic acid and chemically modified.
By processing various types of polymers, electrospinning technology is thus used to produce products with various properties. This makes electrospinning technology widely used in various applications.
| Type | Name | Abbreviation |
| Natural | Alginate | Al |
| Hyaluronic acid | HA | |
| Collagen | CLG | |
| Gelatin | GEL | |
| Chitosan | CS | |
| Fibrinogen | FGN | |
| Synthetic | Polyvinyl alcohol | PVA |
| Polyvinylidene fluoride | PVDF | |
| Polyvinylpyrrolidone | PVP | |
| Polyacrylonitrile | PAN | |
| Polycaprolactone | PCL | |
| Polyethersulfone | PES | |
| Polyethylene oxide | PEO | |
| Polyethylene terephthalate | PET | |
| Polyglycolic acid | PGA | |
| Polylactic acid | PLA | |
| Polylactic-co-glycolic acid | PLGA | |
| Polytetrafluoroethylene | PTFE | |
| Polydioxanone | PDO | |
| Polyhydroxybutyrate | PHB | |
| Thermoplastic polyurethane | PU | |
| Nylon 6,6 | PA66 | |
| Semi-synthetic | Cellulose acetate | CA |
| Cellulose triacetate | CTA | |
| Polybutylenesuccinate | PBS |
Selecting a variety of solvents
The researchers emphasize that it is important to maintain a uniform solution as a solvent that can dissolve polymers and additives. This is necessary to have consistent properties because the polymer and additives are completely mixed. Ideally, the solvent of the polymer solution should be completely evaporated during the electrospinning process. This will form the fibers in their correct shape. However, if the solvent does not completely evaporate, the fibers may become wet and fiber-fiber fusion may occur. This phenomenon lowers the quality of the fibers and also affects the performance of the products.
Among the properties of a solvent, the most important are its boiling point, conductivity, and vapor pressure. Using a solvent with a low boiling point can completely evaporate. By doing so, the fiber will not get wet and the desired result can be obtained during the process. However, if the solvent evaporates too quickly, the polymer may block the needle and interfere with the entire process. To solve this problem, researchers can choose a solvent with a lower vapor pressure. This can control the evaporation rate of the solvent and minimize any problems that may occur during the process.
In addition, the diameter of the fiber is affected by the boiling point and conductivity of the solvent. In general, solvents with low conductivity and low boiling points tend to form high fiber diameters. This is an important factor in determining the physical properties of a fiber and directly affects the quality and performance of the product.
| Solvent name | Solvent abbreviation |
| Acetic acid | AA |
| Acetone | ACE |
| Chloroform | CF |
| Dichloromethane | DCM |
| Dimethyl sulfoxide | DMSO |
| Ethanol | EtOH |
| Ethyl acetate | EA |
| Formic acid | FA |
| Glycerol | Glyc |
| Hexane | Hex |
| 1,1,1,3,3,3-Hexafluoro-2-propanol | HFP |
| Isopropyl alcohol | IPA |
| Methanol | MeOH |
| Methyl acetate | MA |
| N-Methyl-2-pyrrolidone | NMP |
| N,N-Dimethylacetamide | DMAc |
| N,N-Dimethylformamide | DMF |
| Tetrahydrofuran | THF |
| Water | W |
Applications
The researchers emphasize that it is important to maintain a uniform solution as a solvent that can dissolve polymers and additives. This is necessary to have consistent properties because the polymer and additives are completely mixed. Ideally, the solvent of the polymer solution should be completely evaporated during the electrospinning process. This will form the fibers in their correct shape. However, if the solvent does not completely evaporate, the fibers may become wet and fiber-fiber fusion may occur. This phenomenon lowers the quality of the fibers and also affects the performance of the products.
Among the properties of a solvent, the most important are its boiling point, conductivity, and vapor pressure. Using a solvent with a low boiling point can completely evaporate. By doing so, the fiber will not get wet and the desired result can be obtained during the process. However, if the solvent evaporates too quickly, the polymer may block the needle and interfere with the entire process. To solve this problem, researchers can choose a solvent with a lower vapor pressure. This can control the evaporation rate of the solvent and minimize any problems that may occur during the process.
In addition, the diameter of the fiber is affected by the boiling point and conductivity of the solvent. In general, solvents with low conductivity and low boiling points tend to form high fiber diameters. This is an important factor in determining the physical properties of a fiber and directly affects the quality and performance of the product.
• tissue engineering
• wound dressing
• pharmaceutic
• DDS (drug delivery systems)
• Li-Batteries
• Fuel-Cell
• Energy harvesting
• Air purifier
• Disposable filter
• VOCs capture
• filter media (HEPA~ULPA)
• functional clothing
• Water treatment
• Gas Sensors
• Electrochemical Biosensors
• Piezoelectric Sensor
• Highly Sensitive Optical Sensors
• EMI Shielding
• functional protective clothing
• Gas mask filter
• face mask
• skin care
• eye patch
• wearable electronics
• flexible electronics
• EMI Shielding
