presentation-modified- final - mode.ppsx

Dr. Mohamed El-Newehy
Electrospinning; Historical Background,
Fabrication and Applications
Associate Professor
Current Address:
Department of Chemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
http://fac.ksu.edu.sa/melnewehy
Date : Tuesday; June 20, 2017
Time : 14 – 16
Location : Department of Chemistry, Faculty of Science
Tanta University
Department of Chemistry, Faculty of Science, Tanta 31527, Egypt.
melnewehy@science.tanta.edu.eg
TU

Electrospinning process
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The process of spinning fibers with the help of electrostatic forces.

Outlines
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Electrospinning Technique.
Nanofibers Made From Polymers and Metal Oxides.
Factors Affecting the Preparation of Electrospun Nanofibers
Large Scale Production of The Electrospun Nanofibers
Applications of Electrospun Nanofibers.
Historical Background.
Electrospun Nanofibers Architectures
& Control of Various Morphologies

Background
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 Electrospinning = Electrostatic spinning
 Electrospinning uses an electrical charge to draw
very fine (typically on the micro or nano scale) fibers
from a liquid.
 Electrospinning can be viewed as a special case
of electrospraying.

Historical Background
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 Electrospraying

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 William Gilbert (1500s)
o He set out to describe the behavior of magnetic and electrostatic phenomena.
(24 May 1544 – 30 November 1603), was an English physician, physicist and natural philosopher.
o He observed that when a suitably electrically charged piece of amber was
brought near a droplet of water it would form a cone shape and small
droplets would be ejected from the tip of the cone: this is the first recorded
observation of electrospraying.

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 Raleigh (1885)
o The amount of charge required for the deformation of droplets was described by
Lord Raleigh.
 J.F. Cooley (1902) and W.J. Morton (1903)
o In 1902 and 1903, Cooley and Moore described in patents, apparatus for spraying of
liquids by use of electrical charges.

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 John Zeleny (1914)
o His effort began the attempt to mathematically model the behavior of fluids under
electrostatic forces.
 Hagiwaba (1929)
o The preparation of artificial silk by electrical charges was described by Hagiwaba.
o Zeleny reported that the fine fiber-like liquid jets could be emitted from a charged
liquid droplet in the presence of an electrical potential, which is considered to be
the origin of principle for the modern needle Electrospinning.

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 Anton Formhals (1934-1944)
o In 1934, a crucial patent, revealing the experimental apparatus for the practical
production of artificial filaments using electrical field was issued for the first time by
Formhals.
Fabrication of textile yarns and a
voltage of 57 kV was used for
electrospinning cellulose acetate
using acetone and monomethyl ether
of ethylene glycol as solvent.
 C.L Norton (1936)
o Electrospinning from a melt rather than a solution was patented by C.L Norton using
an air-blast to assist fiber formation.

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 Geoffrey Ingram Taylor (1960s)
o Taylor produced the theoretical underpinning of electrospinning.
Geoffrey Ingram Taylor (7 March 1886 – 27 June 1975) was a British physicist and mathematician
o Taylor’s work contributed to electrospinning by mathematically modelling the shape
of the cone formed by the fluid droplet under the effect of an electric field. (Taylor
cone)
When a small volume of electrically
conductive liquid is exposed to an electric
field, the shape of liquid starts to deform from
the shape caused by surface tension alone.
Taylor cone is a consequence of induced charge relaxation
to the free surface of the liquid at the exit of the nozzle

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 Taylor cone

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 1970s
o Some attempts at commercialization were undertaken.
For example:
- Simm, from the Bayer company, submitted a series of patents on
electrospinning of plastics.
- Companies such as Donaldson Company and Freudenberg have
already applied the outcome of electrospinning process in their air
filtration products since past two decades.
o A variety of electrospinning setups were suggested in early
electrospinning setups that have some similarities to recent efforts.

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o Several research groups, especially the Reneker’s group (The University of Akron),
revived electrospinning by demonstrating the fabrication of ultra-thin fibers from
various polymers.
 Industry vs. Academia
o Academia picked-up electrospinning slowly in the 1990s.

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 Growing Popularity of Electrospinning (1994-2013)
202171

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 Milestone in Electrospinning
1902 • Solution electrospinning
1981
• Emulsion electrospinning
• Electrospinning nanocomposites
• Melt electrospinning
1999
• Theoretical model for electrospinning Jet formation
• Scaffolds for tissue engineering
• Aligned nanofibers
2002 • Drug delivery and Ceramic nanofibers
2003 • Core-shell electrospinning
• Drug eluting nanofibers
• Growth factor released nanofibrous scaffolds
• Guiding effect of aligned electrospun nanofibers on human cells
2007

Outlines
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Electrospinning Technique.
Nanofibers Made From Polymers And Metal Oxides.
Factors Affecting the Preparation of Electrospun Nanofibers
Large Scale Production of The Electrospun Nanofibers
Applications of Electrospun Nanofibers.
Historical Background.
Electrospun Nanofibers Architectures
& Control of Various Morphologies

Electrospinning Technique
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 Electrospinning Process

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 Typical Electrospinning

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 Coaxial Electrospinning

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 Emulsion Electrospinning

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 Electrospinning process – Needleless

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 Electrospinning process - stationary wire electrode
stationary wire electrode system as found in industrial

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 Electrospinning offers advantages like
o Simplicity,
o Low cost,
o High efficiency,
o High yield,
o Control over morphology, porosity and composition.
o Nanofibers with of 40-2000 nm can be produced by selecting suitable
combination of polymer and solvent to be used.

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 Welcome To World Nanofibers

Electrospun Nanofibers Architectures
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CONTROL OF VARIOUS MORPHOLOGIES
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As for controlling of morphologies, design of spinnerets and collectors are very important.
All electrospinning equipments accept 5 types of collectors such as plate, rotating disc, drum, mandrel,
and variable polar collectors.
Each collector can be replaced with other one.
Users can select the suitable collector up to their requirements
MECC Co. , Japan

Factors affecting the preparation of Electrospun nanofibers
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1. Concentration
2. Molecular Weight
3. Viscosity
4. Surface Tension
5. Conductivity/Surface Charge Density
A. Solution Parametres
B. Processing Parameters
C. Ambient Parameters
1. Voltage
2. Flow Rate
3. Collectors
4. Tip-to-Collector Distance (TCD)
1. Humidity
2. Temperature

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A. Solution Paramètres
1. Concentration
The concentrations of polymer solution play an important role in the fiber formation during the
electrospinning process.
1. Very low concentration;
- Polymeric micro (nano)-particles will be obtained.
- At this time, electrospray occurs instead of electrospinning owing to the low viscosity and
high surface tensions of the solution.
2. Little higher concentration;
a mixture of beads and fibers will be obtained

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1. Concentration
3. Suitable concentration;
Smooth nanofibers can be obtained.
4. Very high concentration;
not nanoscaled fibers, helix-shaped microribbons will be observed
- Usually, increasing the concentration of solution, the fiber diameter will increase if the solution
concentration is suitable for electrospinning.
- Additionally, solution viscosity can be also tuned by adjusting the solution concentration.

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2. Molecular Weight
Molecular weight reflects the entanglement of polymer chains in solutions, namely the solution
viscosity.
- Lowering the molecular weight of the polymer trends to form beads rather than smooth fiber.
- Increasing the molecular weight, smooth fiber will be obtained.
- Further increasing the molecular weight, micro-ribbon will be obtained
a) 9000–10,000 g/mol; b) 13,000–23,000 g/mol; c) 31,000–50,000 g/mol
(solution concentration: 25 wt. %)

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1.3 wt. % 15 wt. %
3. Viscosity (determining the fiber morphology)
- Continuous and smooth fibers cannot be obtained in very low viscosity.
- Very high viscosity results in the hard ejection of jets from solution, namely there is a requirement
of suitable viscosity for electrospinning.
Generally, the solution viscosity can be tuned by adjusting the polymer concentration of the
solution; thus, different products can be obtained.

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a) Ethanol; b) MC; c) DMF
TEM images of the PVP electrospun nanofibers.
The concentration is 4 wt. %.
4. Surface Tension
In 2004, Yang and Wang systematically investigated the influence of surface tensions on the
morphologies of electrospun products with PVP as model with ethanol, DMF, and MC as solvents.
Solvents may contribute different surface tensions.

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4. Surface Tension
a) 65/35, b) 50/50, c) 35/65,
TEM images of PVP (4 wt. %) nanofibers electrospun from ethanol/DMF solution with
different mass ratios:
- The surface tension and solution viscosity can been adjusted by changing the mass ratio of
solvents mix and fiber morphologies.
- Basically, surface tension determines the upper and lower boundaries of the electrospinning
window if all other conditions are fixed.

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Beaded nanofibers Bead-free nanofiber by adding 0.44 % pyridine
SEM images of the electrospun products from 2 wt. % nylon-4, 6/formic acid solution.
5. Conductivity/Surface Charge Density
- Solution conductivity is mainly determined by the polymer type, solvent sort, and the salt.
- Additionally, the electrical conductivity of the solution can be tuned by adding the ionic salts like
KH2PO4, NaCl, and so on.
- With the aid of ionic salts, nanofibers with small diameter can be obtained.

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Nasser A.M. Barakat, Muzafar A. Kanjwal, Faheem A. Sheikh, Hak Yong Kim. Polymer 50 (2009) 4389–4396
FE-SEM images showing the spider-net in the electrospun nanofiber mats of Nylon-6 in formic/acetic acid, containing 1.5 wt% salt.
NaCl (A and B)
KBr (C and D)
CaCl
2
(E and F)
- NaCl, KBr, and CaCl2 are
strong ionic salts.
- have high dissociation
rates especially in the
aqueous solutions.
o Effect of ionic salts

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o Impact of the salt nature
- Metallic salts of some organic acids have tendency to form sol–gel (e.g. nickel
acetate and cobalt acetate
SEM images for the PVA/NiAc nanofibers mats
After calcination in Ar atmosphere
Before calcination
B.M. Thamer, M.H. El-Newehy, N. A.M. Barakat, M.A. Abdelkareemd, S.S. Al-Deyab, and H.Y. Kim. Electrochimica Acta 142 (2014) 228–239

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FE-SEM images showing the spider-net in the electrospun nanofiber mats of Nylon-6 in formic/acetic acid,
containing 1.5 wt% salt, H2PtCl6.
o Impact of the salt nature
- Weak metallic acid was used; hydrogen hexacholorplatinate solution (H2PtCl6), It
cannot form a sol–gel in the polymeric solution.
The synthesized spider-nets are trivial compared with those obtained in the
case of using the inorganic salts

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FE-SEM images of electrospun polyurethane nanofiber mat containing 1.5 wt% salt, NaCl.
o Effect of polymer solution
- PU solution in THF/DMF.
- THF/DMF have very low polarity compared to water and do not react with the inorganic salts.
- Small parts of spider-net were formed due to low ionization of the used salts in the PU
solution.

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Diameters of some fibers in the synthesized spider-net in case of 1.5 wt% salt, NaCl (A) and CaCl2
(B) of Nylon-6.
o Effect of salt kind and concentration on fiber diameter
The average diameter of the nanofiber in the spider-net synthesized is almost
independent on both of salt kind and concentration.

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FE-SEM images after mixing times; 0.5, 3 and 24 h for PVA/NaCl (A, B and C)and for nylon-6/NaCl (D, E and
F). Salt concentration is 1.5 wt.%.
o Effect of stirring time
At 0.5 h; there is no spider-nets can be observed and salt nanoparticles are apparent attaching to the
nanofibers. (stirring time was not enough to liberate ions on the solution).
At 3 h; spider-net starts to appear.
At 24 h (long time stirring); much spider-net was formed and no salt nanoparticles could be observed.
At 0.5 h; some salt nanoparticles are apparent and also spider-net is formed (fast dissociation of the salt in
acid medium).
At 3h; decrease the amount of the salt nanoparticles.
At 24 h; completely dissolve the salt.

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1. Voltage
- Only the applied voltage higher than the threshold voltage, charged jets ejected from
Taylor Cone, can occur.
- However, the effect of the applied voltages on the diameter of electrospun fibers is a
little controversial.
- For example;
Reneker and Chun have demonstrated that there is not much effect of electric field on
the diameter of electrospun polyethylene oxide (PEO) nanofibers.
B. Processing Parametres
Reneker DH, Chun I (1996) Nanometre diameter fibres of polymer, produced by electrospinning. Nanotechnology 7(3):216–223.

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Several groups suggested that higher voltages facilitated
the formation of large diameter fiber.
For example;
Zhang et al. investigated the effect of voltage on
morphologies and fiber diameters distribution with
poly(vinyl alcohol) (PVA)/water solution as model.
Effect of voltage on morphology and fiber diameter
distribution from a 7.4 wt. % PVA/water solution (DH = 98
%, tip–target distance = 15 cm, flow rate = 0.2 mL/h).
Voltages: a) 5; b) 8; c) 10; d) 13 kV.
Zhang C, Yuan X, Wu L, Han Y, Sheng J (2005). Eur Polym J 41(3):423–432.

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2. Flow Rate
- Generally, lower flow rate is more recommended as the polymer solution will get enough time for
polarization.
- If the flow rate is very high, bead fibers with thick diameter will form rather than the smooth fiber
with thin diameter owing to the short drying time prior to reaching the collector and low
stretching forces.
SEM images of the effect of the flow rate on the morphologies of the PSF fibers from 20% PSF/DMAC
solution at 10 kV. Flow rates of A and B are 0.40 and 0.66 mL/h,
Buchko CJ, Chen LC, Shen Y, Martin DC (1999) Polymer 40(26):7397–7407.

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3. Collectors
- Collectors usually acted as the conductive substrate
to collect the charged fibers.

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4. Tip-to-Collector Distance (TCD)
- If the distance is too short, the fiber will not have enough time to solidify before
reaching the collector.
- If the distance is too long, bead fiber can be obtained.
SEM images of the electrospun PSF fibers from 20wt.% PSF/DMAC solution at 10 kV with different
distances. The distances of A and B are 10 and 15 cm, respectively. The diameters of A and B are
438±72 and 368±59 nm,

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C. Ambient Parametres
1. Humidity
Ambient parameters can affect the fiber diameters and morphologies.
- Low humidity may dry the solvent totally and increase the velocity of the solvent
evaporation.
- High humidity will lead to the thick fiber diameter owing to the charges on the jet can
be neutralized and the stretching forces become small.
- The variety of humidity can also affect the surface morphologies of electrospun
nanofibers.

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C. Ambient Parametres
2. Temperature
- Increasing temperature favors the thinner fiber diameter.
SEM images of the electrospun PA-6-32 fibers under different temperatures.
The temperatures of A and B are 30 and 60 °C, respectively. The diameters of A and B are 98 and
90 nm

Nanofibers made from polymers and metal oxides
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Electrospinning of polymer + solvent system

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oPAN Fibers
- Polyacrylonitrile (PAN) polymer nanofibers in DMF were prepared by electrospinning
technique (V = 9kV, TCD = 7 cm).
- The diameters of the fibers are in the range of 50–320 nm.
SEM images of PAN nanofibers

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oPVA/PEO Fibers
M. El-Newehy, S. Al-Deyab, E.-R. Kenawy, and A. Abdel-Megeed, Fibers and Polymers, 13(6), 709-717, 2012.
SEM images of electrospun nanofibers containing MTZ; (a) electrospun mat; (b)
electrospun mat-alc; (c) electrospun mat-h.
a b c
- Fabrication of electrospun nanofibers based on PVA/PEO blend.
- Stabilization of electrospun PVA/PEO nanofibers against disintegration in water by
heating in oven at 110ºC, or by soaking in isopropyl alcohol for 6 h.

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oNylon-6 Fibers
- Nanospider technology for the production of Nylon-6 nanofibers from formic acid
M. El-Newehy, S. Al-Deyab, E.-R. Kenawy, and A. Abdel-Megeed. Journal of Nanomaterials, Vol. 2011, Article ID 626589, 8 pages, 2011.
SEM images of electrospun nylon-6 nanofiber containing.

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oSilk /PEO
Silk/PEO
Dexamethasone
TEM images of Silk/PEO nanofibers
with dexamethasone
W. Chen, D. Li, A. EI-Shanshory, M. El-Newehy, H.A. EI-Hamshary, S.S. Al-Deyab, C. He, X. Mo. Colloids and Surfaces B: Biointerfaces, 126, 561-568, 2015

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oPVA/CoAc
SEM images for the PVA/CoAc nanofibers mats.
B.M. Thamer, M.H. El-Newehy, S.S. Al-Deyab, M.A. Abdelkareem, H.Y. Kim, N.A.M. Barakat. Applied Catalysis A: General 498 (2015) 230–
After calcination in
Ar atmosphere at
850°C
Before calcination
Urea content
(A) 0.0% (B) 1.0%.

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oAlumina Nanofibers
- Alumina nanofibers were prepared using PVA as polymer precursor and aluminium
acetate as alumina precursor.
SEM images of PVA/Al acetate
nanofibers
SEM images of Alumina
nanofibers heat treated at
900°C.
SEM images of Alumina nanofibers
heat treated at 1300°C.
Electrospinning (TCD = 10 cm, flow
rate = 1.3 mL/h, humidity 50–60
beaded structure due to loss
of organics leaving the
unsintered alumina phase)
the diameters of the fibers are
further reduced due to sintering
- The prepared nanofibers were heat treated at 900°C and 1300°C in order to remove the
organics to generate pure alumina nanofibers.

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oBarium Titanate (BaTiO3) Nanofibers
- Applications as dielectric capacitors, non-volatile ferroelectric random access memories,
transducers, sensors and actuators, solid oxide fuel cells etc
SEM images of electrospun Barium titanate
nanofibers
The calcined BaTiO3 nanofibers are found to be
coarse, brittle and diameter reduced by 12 %
Fibers cylindrical, smooth with diameters
in the range of 50–400 nm
- BaTiO3 nanofibers were prepared from a homogeneous viscous solution of barium acetate +
titanium isopropoxide + polyvinylpyrolidone (PVP) solutions by electrospinning technique ( V = 9
kV, TCD = 7cm).
SEM images of heat treated electrospun
Barium titanate nanofibers

Large scale production
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o The major challenge associated with electrospinning is its production
rate, compared with that of conventional fiber spinning.
o Solvent recovery in large-scale electrospinning is a crucial issue, which
has limited the industrialization of this technology.
o Although melt electrospinning can eliminate solvent recycle problems,
the majority of fibers produced by melt electrospinning have relatively
large diameters.
To date there have been no reports on the mass production of nanofibers
from melt polymers.

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o However, the understanding of the scale-up possibility of the
electrospinning process is still in its infancy.
o Here we summarize recent advances regarding the enhancement of
electrospinning throughput with special emphasis on multiple jets from
multi-needles and the free surface of polymer solutions.

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BUBBLE ELECTROSPINNING FOR MASS PRODUCTION OF NANOFIBERS
The experimental setup of the aerated
solution electrospinning
o The polymer solution was added into the
reservoir.
o Open the gas pump carefully until multiple
bubbles were formed on the liquid surface.
o Then turn on the DC high voltage generator.
o When the applied voltage was increased to the
threshold voltage, there were multiple jets
towards the collector from the bubbles.
o The experiment was carried out at room
temperature.

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Bubble Electro spinning
Advantages
- More bubbles can produce more jets.
- Production rate could be higher than that in the
ordinary e-spin process
- One nozzle produce several bubbles
easy manufacture,
easy operation,
low cost,
high throughput, etc
Disadvantages
- The arrangement of the electrospun fibers was in
disorder.
- Trajectory ejecting jets were so thick that the
mixture solvent had no time to volatilize
completely because of water in the solvent
New bottom-up electro spinning
The minimum diameter of nanofibers was
50nm.

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MULTI-NOZZLE CONSTRUCTIONS
Schematic (a) and photograph (b) of a multi-nozzle spinning head by NanoStatics

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Advantage
Stable electro spinning process
from each Needle
Disadvantage
Interference between jets, non-
uniform Nano fibers
deposition
SEVEN- AND NINE- NEEDLEs WITH LINEAR ARRAY

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NANOSPIDER TM
FREE LIQUID SURFACE ELECTROSPINNING
Advantage
- No clogging
- Production rate
1.5 g min−1
m−1
Disadvantage
- Loose control of solution
feeding

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NANOSPIDER TM
FREE LIQUID SURFACE ELECTROSPINNING

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Nozzle-less production electrospinning line (NanospiderTM)
The nozzle-less principle using rotating electrodes has been developed into a commercially
available industrial scale
NOZZLE-LESS ELECTROSPINNING UNIT

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COMPARISON OF NOZZLE VS NOZZLE-LESS ELECTROSPINNING

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ELECTROSPINNING SETUP WITH A DYNAMINC LIQUID COLLECTOR
Advantage
- Twists imparted on nanofibre bundle liquid
recycling
- Production rate
57–76 m min−1
Disadvantage
- Polymers to be electrospun should not be
soluble in the liquid bath
- No drying device

Applications of Nanofibers
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Applications
of Polymer
Nanofibers
Biomedical Applications
Solar cells
Protective
Clothing
Sensors
Nanocomposites
Optical/Electrical
Applications
Super Conductive
Nanofibers
Filter Media

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Applications of polymer and ceramic
nanofibers

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Electrospinning Electrospun nanofibers encapsulated with drug
Applications
Wound dressing & healing

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Drug delivery
Controlled release is an efficient process of delivering drugs in medical
therapy.
It can balance the delivery kinetics, minimize the toxicity and side effects,
and improve patient convenience
In a controlled release system;
- The active substance is loaded into a carrier or device first
- and then releases at a predictable rate in vivo when administered by an
injected or non-injected route.

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Drug delivery
 Electrospun nanofibers have exhibited many advantages;
- The drug loading is very easy to implement via electrospinning process (More than one
drug can be encapsulated and the high applied voltage used in the electrospinning process had
little influence on the drug activity).
- The high specific surface area
- Short diffusion passage length give the nanofiber drug system higher overall release
rate than the bulk material (e.g. film).
 The release profile can be finely controlled by modulation of nanofiber morphology,
porosity and composition.

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Drug delivery
 Nanofibers for drug release systems mainly come from
- biodegradable polymers, such as PLA, PCL, poly(D-lactide)(PDLA), PLLA, PLGA
- hydrophilic polymers, such as PVA, PEG and PEO.
- Non-biodegradable polymers, such as PEU.
 Model drugs that have been studied include;
- Water soluble
- poor-water soluble
- water insoluble drugs.
 The release of macro-molecules, such as DNA and bioactive proteins, from nanofibers
was also investigated.

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Drug delivery
Many factors may influence the release performance, such as
- Type of polymers used
- Hydrophility and hydrophobicity of drugs and polymers,
- solubility,
- drug polymer comparability,
- additives, and the existence of enzyme in the buffer solution.
 In most cases, water soluble drugs, including DNA and proteins, exhibited
an early-stage burst.

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Drug delivery
 The early burst release can also be lowered via
- The polymer shell can also be directly applied, via a coaxial co-electrospinning
process, and the nanofibers produced are normally named “core-shell”.
- Water-in-oil emulsion can be electrospun into uniform nanofibers, and drug
molecules are trapped by hydrophilic chains.
- Encapsulating water soluble drugs into nanoparticles, followed by incorporating the
drug-loaded nanoparticles into nanofibers.
 In addition, the rate of releasing a water soluble drug could be slowed down when
nanofiber matrix was crosslinked.

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Drug delivery
 The use of electrospun fibers as drug carriers may be attributed to the
work of Kenawy et al. in 2002.
o They investigated delivery of tetracycline hydrochloride based on
the fibrous delivery matrices of poly(ethylene-co-vinyl acetate)
(PEVA), poly(lactic acid) (PLA) and their mixtures.
Kenawy, E.-R., Bowlin, G.L., Mansfield, K., Layman, J., Simpson, D.G., Sanders, E.H., and Wnek, G.E., Journal of Controlled Release, 2002. 81(1-2): p. 57-64.
o Electrospun PEVA showed the highest releasing rate which was
65% of its drug content within 100 h
and the electrospun PEVA/PLA (50/50) released about 40% over the
same time period,
whereas electrospun PLA fibers exhibited negligible release over 50
h.

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Drug delivery
 The first issued patent on drug delivery system using electrospun nanofibers is
attributed to the work of Belenkaya in 2003.
o Silver sulfadiazine, which is useful for the treatment of burns, was added to the
poly(D,L-lactide-coglycolide) (PLG) and poly(N-vinyl pyrrolidone) (PVP) blend
(PLG/PVP: 20/80 w/w).
Belenkaya, B.G., Sakharova, V.I., Polevov, V.N.: US2003069369 (2003).
o The drug-containing blend was fabricated into nanofibers by electrospinning to
yield a 1% silver sulfadiazine concentration in the final matrix.
o The prepared nanofibrous membrane with drug possessed a thickness around 1.5-
2.0 μm and a surface density around 5 mg/cm2
.
o The biodegradation of PLG/PVP electrospun nanofibers in vivo took 3-8 days.

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Wound Dressing
 Polymer nanofibers can also be used for the
treatment of wounds or burns of a human skin, as
well as designed for haemostatic devices with some
unique characteristics.
 With the aid of electric field, fine fibers of
biodegradable polymers can be directly
sprayed/spun onto the injured location of skin to
form a fibrous mat dressing.
Nanofibers for wound dressing
(www.electrosols.com).

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Why Electrospun Nanofibers For Wound Dressing?
 High porosity of electrospun nanofibers
Which allows gas exchange
 Fibrous structure
That protects wounds from infection and dehydration.
 Non-woven electrospun nanofiberous membranes for wound dressing usually have pore
sizes in the range of 500-1000 nm.
Which is small enough to protect the wound from bacterial penetration.
 High surface area of electrospun nanofibers
Is extremely efficient for fluid absorption and dermal delivery.

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Tissue Engineering Scaffold
 One of the challenges to the field of tissue engineering/ biomaterials is the design of ideal
scaffolds/synthetic matrices that can mimic the structure and biological functions of the
natural extracellurlar matrix (ECM).
 The purpose is to repair, replace, maintain, or enhance the function of a particular tissue
or organ

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 The core technologies intrinsic to this effort can be organized into three
areas:
- cell technology
- scaffold construct technology
- technologies for in vivo integration.
 The scaffold construct technology focuses on designing, manufacturing
and characterizing three-dimensional scaffolds for cell seeding and in
vitro or in vivo culturing.

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__
 There are a few basic requirements that have been widely accepted for designing
polymer:
- a scaffold should possess a high porosity, with an appropriate pore size distribution.
- a high surface area is needed.
- biodegradability is often required, with the degradation rate matching the rate of neo-tissue
formation.
- the scaffold must possess the required structural integrity to prevent the pores of the scaffold
from collapsing during neo-tissue formation, with the appropriate mechanical properties.
- the scaffold should be non-toxic to cells and biocompatible, positively interacting with the
cells to promote cell adhesion, proliferation, migration, and differentiated cell function.

Encapsulation of Cells into Electrospun Nanofibers
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__
 The ability to electrospin scaffolds of living organisms will be
useful for the development of novel bioengineering to medical
applications.
 Biohybrid materials: containing or composed of both biological
and non-biological components.
 Recently, there has been a greatly increased interest in using
bacterial viruses as an alternative to bacterial antibiotics and as
vectors for gene delivery (viral and non-viral vectors)
W. Salalha, J Kuhn, Y Dror and E Zussman. Nanotechnology 17 (2006) 4675–4681

Encapsulation of Cells into Electrospun Nanofibers
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__
W. Salalha, J Kuhn, Y Dror and E Zussman. Nanotechnology 17 (2006) 4675–4681
 The encapsulation of biological material while preserving its
activity is important for many applications.
 Challenge:
o The conditions of the electrospinning process that allow the
encapsulation of intact bacteria and bacterial viruses while
maintaining their viability.
o However, the longevity of functional bacteria is limited once
they have been isolated from their native environment.

Energy Applications
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__
Calcination
Novel Electrode
Electrospinning
Applications

Energy Applications;
As Electrode Support for Fuel Cells
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__
Problem Description and Challenges
● Development novel catalyst
● Enhancing active catalyst area
● Development membrane
● Decrease noble metals loading
● Used non-precious metals (Ni, Co, Pd, Fe,…etc)
Poor anode kinetics
Methanol crossover
High cost
Difficulties in DMFC and Solutions
Objectives
The main objectives of this study are:
To fabricate of polymeric electrospun nanofibers containing transition
metals as a new class of materials used as anode electrode in DMFCs
To study the influence of nitrogen doping on the electrocatalytic activity
of introduced catalysts toward methanol oxidation

Energy Applications;
As Electrode Support for Fuel Cells
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__
Method
Step
4
• Preparation of working
electrode
Step
2
• Electrospinning process
Step
3
• Calcination process
Step
1
• Preparation of blend polymer and
metals (sol-gel)

Aerogels
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__
o Aerogels are a diverse class of porous, dry gel, solid materials, extreme low densities
(which range from 0.0011 to ~0.5 g cm-3
) (about 15 times heavier than air).
o Aerogels are open-porous (that is, the gas in the aerogel is not trapped inside solid
pockets).
An aerogel is an open-celled, mesoporous (contains pores ranging from 2 to 50 nm in
diameter), solid foam that is composed of a network of interconnected nanostructures and
that exhibits a porosity (non-solid volume) of no less than 50%.

Aerogels
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Figure 1 | Design, processing and cellular architectures of FIBER NFAs (q¼9.6mgcm3). (a) Schematic showing the synthetic steps. (1) Flexible PAN/BA-a and SiO2
nanofibre membranes are produced by electrospinning. (2) Homogeneous nanofibre dispersions are fabricated via high-speed homogenization. (3)
Uncrosslinked NFAs are prepared by freeze drying nanofibre dispersions. (4) The resultant FIBER NFAs are prepared by the crosslinking treatment. (b) An optical
photograph of FIBER NFAs with diverse shapes. (c–e) Microscopic architecture of FIBER NFAs at various magnifications, showing the hierarchical cellular fibrous
structure. (f) Schematic representation of the dimensions of relevant structures. Scale bars, 20 mm (c), 5 mm (d) and 1 mm (e).

Electrospinning Setup at prc
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Nanospider
NF103

Thank You
Electrospinning is an old but yet
fascinating technique.

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