Advanced
Manufacturing
Choices
ENG 165-265
Spring 2014, Dr. Giulia Canton
Electrospinning
4/13/2015
Content
• Electrospinning
–
–
–
–
Electrospinning Setup
Working Principle
Parameters
Modified Electrospinning Setups
• Near-Field Electrospinning
• Electro-Mechanical Spinning
4/13/2015
Electrospinning
 Electrospinning is a cost-effective method to produce novel fibers with
diameters from less than 3 nm to over 1 mm.
 Common electrospinning setups require only a small amount of
investment, often as low as $2,000.
 To set-up a lab-scale electrospinning unit there is no need of special
laboratory facilities and the space needed is only of the order of 10ft2.
Numbers of
scientific
publications on
electrospinning
from 1995 with
keywords
"electrospinning"
or "electrospun”.
Electrospinning Setup
1. A high voltage power supply
(normally working in a range between
10 and 30kV);
2. A polymer reservoir that can
maintain a constant flow rate of
solution, commonly a syringe
connected to either a mechanical or a
pneumatic syringe pump;
3. A conductive dispensing needle as
polymer source connected to the high
voltage power supply;
4. A conductive substrate, normally grounded, which serves as a collector
for the electrospun fibers.
Electrospinning Setup
Electrospinning Working Principle
Electrospinning –
Taylor cone
Sequence of pictures of the evolution of the shape of a fluid drop with high
electric field applied. The time zero was taken to be the frame in which the jet
first appeared. The electrical potential was applied for a little more than 28 ms
earlier.
D. H. Reneker and A. L. Yarin. Electrospinning jets and polymer nanofibers. Polymer, 49(10):2387{2425, 2008.
Electrospinning –
Bending Instabilities
z
h
Polymer Source
A
The jet is considered to be a series of electrically charged
beads (“computational beads”), with each bead carrying the
same mass of fluid and excess charge.
Stress pulling B back to A (Maxwell fluid)
l
ds
dl E
=E
- s
dt
ldt m
E: elastic modulus
μ: viscosity
Momentum balance of bead B
B
dv
e 2 eV0
m =- 2 + pa 2s
dt
h
l
V0: applied voltage
a: cross section radius
Velocity of bead B
0
Grounded Substrate
dl
= -v
dt
• Reneker, D H. (2000). Bending instability of electrically charged liquid jets of polymer solutions in electrospinning. Journal of applied
physics, 87(9), 4531-.
Electrospinning –
Bending Instabilities
Longitudinal stress in the rectilinear part of the jet and the longitudinal force.
LONGITUDINAL
VISCOELASTIC FORCE
LONGITUDINAL
STRESS
σ
TIME
Bending instability begin to grow
Electrospinning –
Bending Instabilities
Illustration of the instability mechanism.
A
FBC
A
l
l1
B
B
l1
C
Perturbed
polymer jet
B*
δ
θ
FT
l
C
FAB
Coulombic forces , idealized
nodes representation.
Electrospinning –
Model
Electrospinning –
Parameters






10kV
Polymer precursor material.
Solvent and solution additives.
Polymer concentration.
Needle-to-collector distance.
Voltage.
Flow rate.
15kV
To optimize material
properties, fibers thickness,
homogeneity, density, and
distribution.
20kV
Large Scale
Electrospinning
FFES applications
*S. Ramakrishna MaterialsToday 9(3), 40 (2006)
Modified Electrospinning
Setups - Forcespinning
http://fiberiotech.com
Modified Electrospinning
Setups – Aligned fibers
• Rotating Drum
Standard
Collector
Rotating
Drum
Modified Electrospinning
Setups – Aligned fibers
• Electric Field Manipulation
D. Li, Y. Wang, and Y. Xia. Electrospinning of polymeric and ceramic nanofibers as uniaxially aligned arrays. Nano letters,
3(8):1167{1171, 2003.
Modified Electrospinning
Setups – Aligned fibers
• Magnetic Field Manipulation
D. Yang, B. Lu, Y. Zhao, and X. Jiang. Fabrication of aligned fibrous arrays by magnetic electrospinning. Advanced materials,
19(21):3702-3706, 2007.
Near Field Electrospinning
Near Field Electrospinning
• Needle-substrate distance
: < 1cm
• Voltage : 1-5 kV
• Slower yield of nanofibers
• Control individual fibers
patterning
Challenge:
make the fiber thinner
while maintaining the
patterning control.
Sun, D. (2006). Near-field electrospinning. Nano letters, 6(4), 839-.
Electro-Mechanical Spinning
Solution:
Minimize instabilities lowering the
voltage and combine the use of
electrical forces with mechanical
pulling to thin the fiber: ElectroMechanical Spinning (EMS)
This requires:
• Jet initiation step.
• Optimization of the viscoelastic
properties of the polymer solution.
• Control of voltage and stage speed.
Electro-Mechanical Spinning
• Jet Initiation
Electro-Mechanical Spinning
• Voltage
Control
600 V
300 V
Electro-Mechanical Spinning
• Voltage Control
300V
200V
1μm
Bisht GB, Canton G, Mirsepassi A, Kulinsky L, Oh S, Dunn-Rankin D, Madou MJ. Controlled Continuous Patterning of Polymeric Nanofibers on 3D Substrates
Using Low-Voltage Near-Field Electrospinning, Nanoletters, 2011; 11 (4): pp 1831–1837
Electro-Mechanical Spinning
• Stage Speed Control
Stage speed
(mm s-1)
Diameter
(nm)
20
422
40
365
60
204
80
185
Bisht GB, Canton G, Mirsepassi A, Kulinsky L, Oh S, Dunn-Rankin D, Madou MJ. Controlled Continuous Patterning of Polymeric Nanofibers on 3D Substrates
Using Low-Voltage Near-Field Electrospinning, Nanoletters, 2011; 11 (4): pp 1831–1837
Electro-Mechanical Spinning
• Other results
20nm range nanofibers
Suspended nanofibers
Electro-Mechanical Spinning
• Suspended Carbon Nanofibers
Probing pads
Carbon walls
Carbon wall
Suspended Fibers
Carbon wall
20μm
Electro-Mechanical Spinning
• Suspended Carbon Nanofibers
Applications
Questions?
Thank You!