Electrospinning
Technique
by
Assistant Professor
Dr. Akram R. Jabur
Dept. of Materials Eng.
University of Technology
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.
Advantages
Inexpensive and simple
method
Capable of producing
nanofibers
positive terminal
negative terminal
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
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
ELECTROSPINNING
The distribution of charge in the fiber changes
as the fiber dries out during flight
ning Technique
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.
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
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
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.
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.
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)
2 main Properties of fibers produced
A very high surface to volume ratio •
Defect free structure at the molecular level •
Model of Surface-to-Volume
Comparisons…
Single Box Ratio
6 m2
= 6 m2/m3
3
1m
Smaller Boxes Ratio
12 m2
= 12 m2/m3
3
1m
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.
•
Nanofiber Structures
Interconnected structure
(Source: Ramakrishna, S., et.al, 2005)
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
Potential Applications
Tissue engineering scaffolds
- Adjustable biodegradation rate
- Better cell attachment
- Controllable cell directional growth
Wound dressing
Medical prostheses
- Prevents scar
- Bacterial shielding
- Lower stress concentration
- Higher fracture strength
Haemostatic devices
Drug delivery
- Higher efficiency in
fluid absorption
- Increased dissolution rate
- Drug-nanofiber interlace
Cosmetics
- Higher utilization
- Higher transfer rate
Polymer
Nanofiber
Sensor devices
- Higher sensitivity
- For cells, arteries and veins
Filter media
Electrical conductors
- Higher filter efficiency
- Ultra small devices
Protective clothing
Material reinforcement
Optical applications
- Breathable fabric that
blocks chemicals
- Higher fracture toughness
- Higher delamination resistance
- Liquid crystal optical
shutters
NANOFIBERS
Comparison of red blood cell with nanofibers web [1].
NANOFIBERS
Entrapped pollen spore on nanofiber web [1].