Multi-Physics Modeling and Experimental Characterization of Needleless

Electrospinning for Scalable Nanofiber Production (CMMI 1234297)

Electrospinning technique is a low-cost, top-down nanofabrication

technique, which enables to produce ultrathin continuous fibers of

natural and synthetic polymers and polymer-derived carbon, metals,

ceramics, and semiconductor materials with the diameters in the

rang of 1 up to 2,000 nm. Electrospun nanofibers are finding broad

advanced structural and multifunctional applications in variable

industrial sectors. Needleless electrospinning is a continuous,

scalable electrospinning method for low-cost, scalable production

of nanofibers. In this project, multiphysics phase-field modeling is

formulated and related experimentation is performed to understand

the electrohydrodynamic process of needleless electrospinning. The

research will benefit the computer-aided electrospinning

engineering (CAEE) in education, research and industrial

applications.

Xiangfa Wu, Department of Mechanical Engineering, North Dakota State University, Fargo, ND

Needle-based vs. Needleless Electrospinning

PAN NFs Ternary PANI/CNTs/CNFsPAN-based CNFs CNT Yarns CNT-grafted CNFs

Core-shell NFs

Selected Nanofiber Applications

• Advanced & functional composites • Multifunctional textiles

• Fuel cells, Li ion batteries, solar cells, • MEMS/NEMS, sensors, flexible actuators;

supercapacitors, & separators • Biomedical applications, drug delivery,

• High-grade multifunctional filters, wound dressing

oil- water separation membranes • Tissue engineering, tissue scaffolding

Nano-cracked Cr-NFs Graphene-CNFs G/PANI-CNFs PANI-coated CNFs

2 2

0

0

Global Free Energy:

1 1[ ( , ) ( ) | | ( , ) | | ]

2 2

Dieletric Constant:

( , ) ( ) (1 )

( )

Flory Huggins Free Energy :

1/ (1 ) ln ln (1 )

de Gennes's Non

rV

solution air

r r r

FH dG

FH

FH

F f c h c c dV

c c c

f f f

f

f m

2

0

local Interface Energy:

1/ 2 | |

Electrostatic Field:

[ ( , ) ] 0

Ginzburg-Langau Equation (Liquid/Gas Interface):

( ) .[ ( ) / | |]

Modified Navier Stokes Equation (Flow Mot

dG

r

c c m

f

c

cv c M c k c c

t

0

ion)

( . ) . :

Cahn Hilliard Equation (Phase Separation-Cavitation):

( ) .[ ( ) / | |]

Numerical Algorithm: Semi-Implicit Spectral Method

c

m

vv v p c

t

v M k c ct

Hybrid Micro/Nanofiber Filtration Media & Control

Microfiber Sample

Interface Toughening & Damage Self-healing

Superhydrophobic & Superoleophilic Nanofibers

for Oil-Water Separation

Nanofiber Applications, Needleless Emulsion-Electrospinning & Multi-Physics Modeling

DCPD-DMF/PAN-

DMF emulsion

Water Droplets

on PS NFs

Water/Oil Contact

Angle on PVDF NFs

Mulitifunctional Fibrous Supercapacitor Electrodes

Core-shell DCPD/PAN

nanofibers

0

100

200

300

400

500

600

700

800

900

0 15

30

45

60

75

90

105

120

135

150

165

180

Ele

ctri

c F

ield

(V

/m)

Phi (degrees)

180˚

Curved90°

CurvedFlat

Jet Initiation & Electrode Span-Angle on DC Electrical Field

0

2231 4 2 20 *

31

0 0

22

*max 31

0

Jet Initiaton (Jet Spacing)

cos( )exp( / )

1

3

Wave number for fastest growth

1

2

mo

m

o o

mo

m

o o

h h kx t

Uh mAhk k k

h h H h

UmAhk

h h H h

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.950

60

70

80

90

100

110

120

130

140Maximum Height vs Time

Time (seconds)

Heig

ht

(Mic

rom

ete

rs)

Dot DefectsLine Defects

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90

5

10

15

20

25

30

35

40

45

50Minimum Height vs Time

Time (seconds)

Heig

ht (M

icro

me

ters

)

Dot Defects

Line Defects

Jet Growth Rate in Needleless ElectrospinningSurface Dewetting on Jet Initiation

4% 8% 12% 16%4

8

12

16

20

24

0.01"

Cri

tica

l V

olta

ge

(kV

)

PAN Concentration

0.02"

0.04" 0.06"

Collection Distance

(between steel wire & plate)

6.5”

Drop Volume (solution) 2.0 μl

Size of Plate (fiber collector) 12”×12”

Constant Negative Voltage - 2 kV

Diameter of Steel Wires 0.01”, 0.02”,

0.04”, 0.06”

Temperature 20 oC

Solutions PAN/DMF,

PEO/Water

Needleless emulsion spinning for mass production of core-

shell nanofibers

Education & Outreach

• Undergraduate Students: Nicole Reilly (URA), Jeremy Jenniges

(URA), Yesheng Chen (URA), Zheng Fang (URA)

• Native American Tribal College & High-School Students: Shenae

Azure, Darrin Frederick

• Graduate Students: Zhengping Zhou, Meng Yu, Youhao Zhao,

Josh Borglum, Xiao Wang, Zheng Fang

• Two undergraduate senior design groups (6 senior undergraduates)

Collaborations

• Univ. of Illinois-Chicago; North Carolina A & G State Univ.; South

Dakota School of Mines & Tech.; South Dakota State Univ.; Jiangxi

Normal Univ., China

Computational Free-Surface Multi-Jet Initiation

Free-Surface Jet Initiation on Dewetted Surface