d. lukáš 2010 physical principles of nanofiber production 1. needle-less electrospinning 1
TRANSCRIPT
D. Lukáš2010
Physical principles of nanofiber production
1. Needle-less electrospinning
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3.6. Self-organisation of electrospinning jets on free liquid surfaces
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Needle electrospinning:Self-organisation of the fluid in electrospinning is the underlying cause behind formation of the Taylor cone, the stable jet part, the whipping zone and evaporation of solvent.
Now, it will be shown that the self-organising potential of electrospinning is even more forcerful since it has a power to organize :
individual jets on free liquid surfaces without any need to use needless / capillaries to create them.
This finding is enormously attractive regarding the recent effort to elevate electrospinning technology to industrial level because it opens a chance to design simple as well as highly productive lines for nanofibrous layer production.
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4
Epoxy resinEE
no.no.
11 22 33 44
66
1 2 3 4 5 61 2 3 4 5 6
E = 0E = 0E = EE = Ecc
EEcc
A rode instead of a A rode instead of a needleneedle
55
d=1cm
+++
++ ++++
++++++++++++ ++ ++
Stationary wave
F. Sanetrník
Sandra Torres
5
Wave vector
Angular frequency Growth factor
Dynamic phenomenon: field strength increment can lead to unlimited growth of a wave amplitude.
A. SarkarA. Sarkar
tkxiAtx exp,
Amplitude
Clemson University Electrospinning - X-rays 6
ikxAetx t exp, Im
cEE Stable amplitudeStable amplitude
GrowingGrowing amplitude amplitudecEE
tkxiAtx exp, 02
02 Lukas D Sarkar A Pokorny P, SELF ORGANIZATION OF JETS IN ELECTROSPINNING FROM FREE LIQUID SURFACE - A GENERALIZED APPROACH, ACCEPTED FOR PUBLICATION, Journal of Applied Physics, 103 (2008), 309-316.
?,2 kfDispersion lawDispersion law
0E
CEE
D. Lukas, A. Sarkar, and P. Pokorny, Journal of Applied Physics, 103 (2008)
timerelaxation
7
Needleless Electrospinning Prague 2007 8
0202
2
0
kE
xg
t z
Euler equation
gravitationSurface tension
Elektrostatic forces
?2 f
kkEkg 2
022 dispersion law
Velocity potential
/2k
tkxiAtx exp,
0Equation of continuity
Clemson University Electrospinning - X-rays 9
kkEkg 222
Stable waves of various wave numbers and angular frequencies.
Fastest forming instability
The only wave
02
02
Various field Various field strengthsstrengths
tAe Im
cEE
cEE
E
E
Tonks-Frenkel instabilityTonks-Frenkel instability
/0teAtA
Capillary waves
Electrospinning
Relaxation time
qteAtA 0Growth factor 10
11
kkEkg 222 02
02
k
42
4
g
Ec
0k022 gkEk
044222 gEacbD c
Quadratic equation with the only solution
02 cbxax
Critical field strength
12
42
4
g
Ec
g
Ec22
gEc 2
2
1
ga
aEc
2
2
1ce pp
capillary length
13
2
20Ea
Dimensionless electrospinning number
aEc
2
2
1
12
2
cEa
1c
14
Minimal and negative square values of the angular frequency correspond to the maximal growth factors, q’s, inherently connected with the self-organisation caused by the mechanism of the fastest forming instability.
0/2 dkd
kkEkg 222
6
122222
020
2,1
gEEk
+
15
k/2
6
122222
020
2,1
gEEk
gEE
1222
1222
020
4/3
32
a
dimensionless intra-jet distance
Clemson University Electrospinning - X-rays 16
4/3
32
Clemson University Electrospinning - X-rays 17
Linear clefts emit polymeric jets. Linear clefts in (a) and (b) emit polymeric (polyvinyl alcohol) jets at the voltages, 32 kV and 43 kV, respectively. The inter-jet distance / wavelength is . The distance between the cleft and the collector was adjusted on 802 mm.
b
ba EE 32 kV 43 kV
Clemson University Electrospinning - X-rays 18
Technology
Jirsák, O. Sanetrník, F. Lukáš, D. Kotek, V. Marinová, L. Chaloupek, J. (2005) WO2005024101 A Method of Nanofibres Production from A Polymer Solution Using Electrostatic Spinning and A Device for Carrying out The Method.
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