1. Electrospinning Technique University of Technologyby
Assistant Professor
Dr. Akram R. Jabur
Dept. of Materials Eng.
University of Technology

2. Electrospinning
 Uses an electrical charge to draw very fine  fibres from a liquid.
This method ensures that no solvent can be carried over into the final product.
Ability to produce novel synthetic fibers of small diameter and good mechanical properties.

3. Advantages Inexpensive and simple method Capable of producing
nanofibers
positive terminal
negative terminal

5. Taylor Cone
refers to the cone observed in electrospinning, electrospraying and hydrodynamic spray processes from which a jet of charged particles emanates above a threshold voltage
was described by Sir Geoffrey Ingram Taylor in 1964 before electrospray was "discovered“
to form a perfect cone required a semi-vertical angle of 49.3° (a whole angle of 98.6°) , the shape of such a cone approached the theoretical shape just before jet formation – Taylor Angle

6. Taylor Cone
When a sufficiently high voltage is applied to a liquid droplet, the body of the liquid becomes charged, and electrostatic repulsion counteracts the surface tension and droplet is stretched, at a critical point a stream of liquid erupts from the surface. This point of eruption is known as the Taylor cone

7. ELECTROSPINNING
The distribution of charge in the fiber changes as the fiber dries out during flight

8. ning Technique

9. Advantages
Able to make very thin fibers easily, since the viscosity of many polymer solutions is very low. 
The lower viscosity of sample makes an elongational deformation easily.

10. Disadvantages
The instability of elongational deformation increases with growing deformation of low viscosity polymer solutions. 
Beads are more easily formed as the fiber diameter decreases. Beads formation decreases the surface area of fabrics

11. Process Electrospinning:
A high voltage is passed through a polymer solution inducing an electrostatic repulsion force
The polymer is pumped through an insulin syringe, the repulsion force results in the formation of a thin jet
This jet is directed toward a grounded collection plate, the solvent evaporates before hitting the collection plate and results in the formation of a polymer scaffold
These electrospinning is promising for tissue engineering because it produces a 3-D scaffold with high porosity and large surface to volume ratio.
In the Mills lab: polycaprolacetone (PCL) – polymer
chloroform – solvent

12. Fiber dimension and morphology
The diameter of a fiber produced by electrospinning primarily depends on the spinning parameters.
An increase in solution concentration results in fibers with larger diameters.

13. Parameters
With increasing concentration of the fiber content, increase in mechanical properties. But further increasing it, mechanical properties drops.
With increasing electric potential the fiber diameter decreases, and the fiber diameter distribution becomes increasing broader.

14. Parameters
1. Molecular Weight of the polymer 2. Solution properties (viscosity, conductivity and surface tension) 3. Electric potential, flow rate and concentration 4. Distance between the capillary and collection screen 5. Ambient parameters (temperature, humidity and air velocity in the chamber) 6. Motion of target screen (collector)

15. 2 main Properties of fibers produced
A very high surface to volume ratio
Defect free structure at the molecular level

16. Model of Surface-to-Volume Comparisons…
Single Box Ratio
6 m2
1 m3 =
6 m2/m3
Smaller Boxes Ratio
12 m2
1 m3 =
12 m2/m3
ABC blocks help students to understand the concept of surface to volume ratios. They need to see the additional surfaces!
Neglecting spaces between the smaller boxes, the volumes of the box on the left and the boxes on the right are the same but the surface area of the smaller boxes added together is much greater than the single box.

17. Interconnected structure
Nanofiber Structures
Interconnected structure
There are different types of structures of nanofibers: random, aligned, 3 dimensional (mesh like), porous, hallow, ceramics, beaded, and interconnected. The one we were able to fabricate was a cross between random and interconnected
(Source: Ramakrishna, S., et.al, 2005)

18. Filtration
Polymeric nanofibers have significant applications in the area of filtration since their surface area is substantially greater and have smaller micropores than any other fibers like spun bond and melt blown (MB) webs.
Fiber Type
Fiber size, in micrometer
Fiber surface area per mass of fiber material m2/g
Polymeric Nanofibers
0.05 80
Spunbond fiber 20
0.2
Melt blown fiber
2.0 2

19. Potential Applications
Tissue engineering scaffolds
- Adjustable biodegradation rate
- Better cell attachment
- Controllable cell directional growth
Wound dressing
- Prevents scar
- Bacterial shielding
Medical prostheses
- Lower stress concentration
- Higher fracture strength
Haemostatic devices
- Higher efficiency in fluid absorption
Drug delivery
- Increased dissolution rate
- Drug-nanofiber interlace
Polymer Nanofiber
Sensor devices
- Higher sensitivity
- For cells, arteries and veins
Cosmetics
- Higher utilization
- Higher transfer rate
Filter media
- Higher filter efficiency
Electrical conductors
- Ultra small devices
Protective clothing
Breathable fabric that blocks chemicals
Optical applications
Liquid crystal optical shutters
Material reinforcement
- Higher fracture toughness
- Higher delamination resistance

20. NANOFIBERS
Comparison of red blood cell with nanofibers web [1].

21. NANOFIBERS
  Entrapped pollen spore on nanofiber web [1].