Mechanical Properties of Biopolymer-Based Nanofibers

Alexander L. Yarin
Department of Mechanical and Industrial Engineering
University of Illinois at Chicago
U.S.A.

2
Acknowledgements
This work was supported by a research contract with the United
Soybean Board, Chesterfield, Missouri (research contract no. 0491).
This work is supported by the Nonwovens Institute, grant No. 14-161.
PhD students from the UIC Multiscale Mechanics and Nanotechnology Lab
involved in this work:
Y. Zhang
S. Sinha-Ray
Sh. Khansari
A. Kolbasov
S. Sett
Postdocs:
Dr. M.W. Lee
Dr. S. Duzyer
Dr. S. An
Collaborators:
Dr. B. Pourdeyhimi (North Carolina State University),
Dr. K. Stephansen (Technical University of Denmark)
Dr. S.S. Yoon (Korea University)

Outline
• Solution Blowing of Bio-Waste Derived Nanofibers
• Mechanical Behavior of Soy Protein-Based Nanofiber Mats
• Plant- and Animal-Based Nanofibers
• Effect of Chemical and Physical Crosslinking on Mechanical
Properties of Soy Protein-Based Nanofiber Mats
• Controlled Drug Release (Desorption) from Soy Protein-Based
Nanofiber Mats
• Protection of Pruned Vines from Esca Fungi
• Prevention of Mold Invasion
• Antibacterial Action
• Heavy Metal Ion Adsorption on Biopolymer Nano-Textured
Membranes
• Conclusion 3

Plant- and Animal-Based Protein Biopolymers
Biofuel Byproducts
Cellulose
Cellulose Acetate
ZeinSoy Protein
Silk Sericin
Lignin
Bovine Serum
Albumin,
Fish Protein,
Chitosan
4

5
Plant-Based Biopolymers’ Applications
• Biodiesel
• Bioplastic
• Drug Delivery
• Wound Dressing
• Disinfectants
• Adhesives
• Films
• Textile
• Clear Tapes
• Glass Frames
• Cigarette Filters
• Additives
• Coatings
• Carbon Fiber
• Paper Industry
• Cosmetics
• Adsorbents

Even cars:
6

Solution Blowing of Bio-Waste Derived Nanofibers
Solution blowing setup to produce monolithic and core-shell nanofibers
• Sinha-Ray, S., Yarin, A. L., Pourdeyhimi, B., 2010, Carbon 48, 3575-3578.
• Sinha-Ray, S., Zhang, Y., Yarin, A.L., Davis, S., Pourdeyhimi, B., 2011, Biomacromolecules 12, 2357-2363.
• Khansari, S., Sinha-Ray, S., Yarin, A.L., Pourdeyhimi, B., 2012, Journal of Applied Physics 111, 044906-1-13. 7

Schematic of Solution Blowing Process

Sample Preparation
Nanofibers are collected on
rotating aluminum drum and
cut into rectangular pieces of
10-25 mm wide and 20-40 mm
long. Nanofiber mat thickness
is 0.20-0.30 mm.
Solution-blown sample of soy protein/nylon 6 (70/30 wt/wt%).

Single-nozzle Solution Blowing

Macroscopic Images of Soy Protein Nanofibers
Average diameter of nanofibers is
300-500 nm.

Microscopic Optical Images of Soy Protein Nanofibers:
SP/Nylon 6 Nanofibers Blown from Solution in Formic Acid

Microscopic Optical Images of Soy Protein Nanofibers:
SP/PVA Nanofibers Blown from Aqueous Solution

From Single-Nozzle to Eight-Nozzle Solution Blowing

45 wt% Soy Protein-Nylon 6 Nanofiber Mat:
6 Nozzles for 5 Minutes

Industrial-Scale Solution Blowing of Soy
Protein Nanofiber Mats
A. Kolbasov et al. Industrial & Engineering Chemistry Research 55, 323-333 (2016).

Industrial-Scale Soy Protein Nanofiber Mats

Solution-Blown Monolithic Nanofibers Containing
50% of Bio-Polymer (Soy Protein)
S. Sinha-Ray, Y. Zhang, A.L. Yarin, S.C. Davis, B. Pourdeyhimi,
Biomacromolecules, 12, 2357-2363 (2011).

Solution-Blown Core-Shell Nanofibers with Soy
Protein in the Shell

Sample Preparation and Tensile Tests
100 N capacity Instron machine (model 5942)

Stress-Strain Behavior for Soy Protein/Nylon 6
(40/60 wt%) Nanofiber Mats
Failure stress and strain are in the range of
σxx,rupture=0.4-0.9 MPa and εrupture=4-10%.

Phenomenological rheological constitutive equation:
For an incompressible material:
Phenomenological Model
σ=-PI+τ
σ is stress tensor, P is hydrostatic pressure, and τ is deviatoric stress
Constitutive equation for stress in elastic-viscopastic material:
22
• M. B. Rubin and A. L. Yarin, 1993, J. Non-Newton. Fluid Mech. 50, 79;
Corrigendum: 1995, J. Non-Newton. Fluid Mech. 57, 321.

Phenomenological Model
23
• Prager, W. Duke Math. J. 9, 1942, 228.
Prager Equation
The phenomenological equation for the uniaxial stretching of a planar strip yields
the following stress-strain dependence:

Stress-Strain Behavior of Soy Protein
Nanofiber Mats
Average
width of the
samples (mm)
Average
thickness
of the
samples
(mm)
Average
Young’s
modulus E
(MPa)
Average
yield
stress Y
(MPa)
Average
specific strain
energy
u
(MPa)
Average
maximum
strain at
rupture
εrupture(%)
Average
maximum stress at
rupture
σxx,rupture
12.07 0.20 19.56±6.48 0.56±0.15 2.26±0.71 4.52±0.92 0.67±0.10
24
1, experiment
2, phenomenological model
1, experiment
2, phenomenological model

for(φ,t): the orinetational probability
density function in nanofiber mat.
at t=0, for(φ,t) =1/2π
Solution
for(φ,t) is found from the Fokker-Planck equation:
Micromechanical Model
25

Rupture of Individual Bonds in Mats under
Uniaxial Stretching
26

27
Mat Plasticity as Bond Rupture Process

* fσ /E 0.047=
1-experiment
2,3,4-micromechanical model * fσ /E 0.058=
* fσ /E 0.040=
Soy protein/nylon 6 (40/60 wt/wt %) nanofiber mat’s stress-strain curve fitted with
(a) phenomenological and (b) micromechanical models.
Characterization of Stress-Strain
Behavior for Soy Protein Nanofibers
28

Behavior for Soy Protein Nanofibers
Sample
Width
(mm)
Thickness
(mm)
Young’s
modulus E
(phenomenological
model); MPa
Young’s
modulus E
corresponding to the
micromechanical
model; MPa
Yield
stress of the
phenomenological
model, Y
(MPa)
1 11.91 0.22 12.8 12.8 0.53 0.071
2 11.47 0.22 17.58 17.58 0.46 0.047
3 12.43 0.22 14.26 14.26 0.46 0.058
4 11.47 0.22 20.88 20.88 0.53 0.047
5 11.21 0.22 19.69 19.69 0.6 0.055
6 11.38 0.24 24.01 24.01 0.6 0.047
7 11.53 0.2 38.02 38.02 0.78 0.038
8 11.65 0.22 24.25 24.25 0.53 0.041
9 11.99 0.22 14.87 14.87 0.49 0.058
10 12.01 0.16 21.79 21.79 0.79 0.060
Relative bond rupture
stress of the
micromechanical
model,
* fσ /E
29

Average
width
of the
samples
(mm)
Average
thickness
of the
samples
(mm)
Average
Young’s
modulus E
(MPa)
Average
yield
Stress
Y
(MPa)
Average
specific
strain
energy
u
(MPa)
Average
maximum
strain at
rupture
εrupture(%)
Average
maximum
stress at
rupture
σxx,rupture
11.22 0.15 22.26±6.06 0.57±0.3 0.92±0.02 2.41±0.40 0.54±0.10
1-experiment
2-phenomenological model
Behavior for Core/Shell Soy Protein Nanofibers
30

Behavior for Nylon 6 Nanofibers
Average
width
of the
samples
(mm)
Average
thickness
of the
samples
(mm)
Average
Young’s
Modulus
E
(MPa)
Average
yield
stress
Y
(MPa)
Average
specific
strain
energy
u
(MPa)
Average
maximum
strain at
rupture
εrupture(%)
Average
maximum
stress at
rupture
σxx,rupture
13.00 0.39 14.46±2.30 1.17±0.75 11.71±0.31 11.80±1.39 1.68±0.18
1-experiment
2-phenomenological model
31

32
Biopolymer-Based Nanofiber Mats
Cellulose Acetate/PAN
(50/50 wt %)
(30/70 wt %)
Soy Protein/Zein/Nylon 6
(25/25/50 wt %)
Zein/Nylon 6
(57/43 wt %)
Core/Shell Zein/Nylon 6
70 wt % zein in core
Lignin/Nylon 6
(50/50 wt %)
Zein/Silk Sericin/Nylon 6
(25/25/50 wt %)
Silk Sericin/Nylon 6
(50/50 wt %)
BSA/PVA (50/50 wt %)
(50/50 wt %)
Soy Protein/Zein/Nylon 6
(25/25/50 wt %)
Zein/Nylon 6
(57/43 wt %)
Silk Sericin/Nylon 6
(50/50 wt %)
Zein/Silk Sericin/Nylon 6
(25/25/50 wt %)
Soy Protein/PET
(20/80 wt %)
BSA/PVA (50/50 wt %) Core/Shell Zein/Nylon 6
70 wt % zein in core
S. Khansari, S. Sinha-Ray, A.L. Yarin,B. Pourdeyhimi. Industrial & Engineering
Chemistry Research 52, 15104-15113 (2013).

Solution-Blown Nanofibers from
Fish Sarcoplasmic Protein
33
Solution-blown
FSP/nylon 6
fibers with dry weight
ratios of (a) 10/90,
(b) 25/75,
(c) 50/50,
(d) 75/25,
(e) 90/10.
S. Sett, K. Stephansen, A.L. Yarin. Polymer v.93, 78-87 (2016).

Mechanical Characterization of
34
zein/nylon 6
(40/60 wt%)
core/shell zein
/nylon 6
(70 wt% zein in core)
silk sericin/nylon 6
(50/50 wt%)
soy protein/PET
(20/80 wt%)
zein/nylon 6
(57/43 wt%)
zein/nylon 6
(66/34 wt%)
soy protein/zein
/nylon 6
(25/25/50 wt%)
silk sericin/zein
/nylon 6
(25/25/50 wt%)
lignin/nylon 6
(25/75 wt%)
lignin/nylon 6
(50/50 wt%),
cellulose acetate
/PAN
(30/70 wt%)
pure PET

35
Sample
Content
(wt %)
Solvent
Ave.
Width
(mm)
Ave.
Thickness
(mm)
Ave.
Young’s
Modulus
E; (MPa)
Ave. Yield
Stress
Y; (MPa)
Max.
Strain at
Rupture
(%)
Max.
Stress at
Rupture
(MPa)
Zein/Nylon 40/60
Formic
acid
8.44 0.20 12.53±2.55 0.16±0.07 2.21±0.76 0.19±0.06
Zein/Nylon 57/43
Formic
acid
6.47 0.20 3.38±1.69 0.10±0.02 5.56±1.44 0.13±0.02
Zein/Nylon 66/34
Formic
acid
7.08 0.20 2.16±0.74 0.04±0.01 4.28±0.92 0.06±0.01
Core-Shell Zein
Core:
70/30
Formic
acid
6.44 0.20 6.05±0.69 0.30±0.01 12.22±0.62 0.47±0.03
SP/Zein/Nylon 25/25/50
Formic
acid
6.93 0.20 10.90±2.54 0.23±0.04 5.63±2.37 0.35±0.06
Zein/Silk
Sericin/Nylon
25/25/50
Formic
acid
6.50 0.15 20.46±4.88 0.24±0.05 2.50±0.49 0.35±0.60
Silk
Sericin/Nylon
50/50
Formic
acid
5.29 0.30 11.02±2.16 0.22±0.06 2.73±0.41 0.28±0.07
Lignin/Nylon 25/75
Formic
acid
5.53 0.16 23.39±6.49 0.42±0.08 4.13±1.15 0.61±0.10
Lignin/Nylon 50/50
Formic
acid
6.13 0.15 9.78±2.41 0.22±0.02 13.72±3.76 0.38±0.04
SP/PET 20/80
TFA/AC/
DCM
6.55 0.20 28.59±2.63 0.32±0.11 0.88±0.05 0.27±0.04
Cellulose
AC/PAN
30/70 DMF 7.90 0.15 3.47±2.67 0.23±0.01 4.50±1.17 0.15±0.05
Pure PET 100
TFA/AC/
DCM
7.56 0.20 28.14±3.24 0.37±0.07 2.28±0.31 0.50±0.008
xx
8 2 E
Y tanh
3 3 Y
 
=   
 
σ ε
Mechanical Properties for

Crosslinking of Soy Protein Nanofiber Mats
36
Cross-linking Agents
Formaldehyde Glyoxal Sodium Borohydride Zinc Sulfate
• Sinha-Ray, S., Khansari, S., Yarin, A.L., Pourdeyhimi., B., 2012, Industrial and Engineering Chemistry Research 51, 15109-15121.

(a) 20 wt% formaldehyde
(b) 20 wt% glyoxal
(c) 5 wt% of sodium borohydride
(d) 10 wt% zinc sulfate
(c) (d)
The weight ratio of crosslinking agents to nanofiber samples is 5, 10, and 20 wt %.
Soy protein/nylon 6 (50/50 wt %)
nanofiber mat cross-linked at 80 wt %
glyoxal/nanofiber mat ratio.
Crosslinking of Soy Protein Nanofiber Mats
37

Mechanical Properties of Crosslinked Fibers using
Formaldehyde and Zinc Sulfate
38
Formaldehyde
Zinc Sulfate

Rectangular pieces of nanofiber mats were heated under pressure for 1 min at 55 °C.
1- Non-bonded samples
2- Thermally-bonded samples
Thermal Bonding of Soy Protein Nanofiber Mats
39

Wet Bonding for Soy Protein Nanofiber Mats
Wet samples were compressed under the mass load of 150 g (i.e. under pressure of 6 kPa)
for 24 h at room temperature until they were partially dried.
1- Non-treated samples
2- Wet-conglutinated samples
40

Controlled Drug Release from
Soy Protein Nanofibers
41
Monolithic Soy Protein/Nylon 6
(50/50 wt %)
1 wt % Rhodamine B fluorescent dye is incorporated in nanofiber mats.
Core/Shell
Soy Protein/Nylon 6
Monolithic Soy Protein/PVA
(50/50 wt %)
• Khansari, S., Duzyer, S., Sinha-Ray, S., Hockenberger, A., Yarin, A.L., Pourdeyhimi, B., 2013, Molecular Pharmeceutics 10, 4509-4526 .
• Srikar, R., Yarin, A. L., Megaridis, C. M., Bazilevsky, A. V., Kelly, E., 2008, Langmuir 24, 965-974.

Soy Protein (50 wt%) Nanofibers Containing Rhodamine B Fluorescent Dye as a
Model Drug vs. Riboflavin-Containing Nanofibers
Sh. Khansari et al. Molecular Pharmaceutics 10, 4509-4526 (2013).

Images of Rhodamine B-Loaded Nanofibers
43
Before Water Immersion
After Completion of
Release Experiments
Monolithic Nylon 6
Nanofibers
Monolithic Soy Protein/Nylon 6
(50:50) Nanofibers
Monolithic Soy Protein/PVA
(50:50) Nanofibers
Monolithic soy protein/nylon 6
+ 10 wt% PEG Nanofibers
Core/Shell Soy Protein/Nylon 6
Nanofibers
+10 wt% PEG Nanofibers
Before Water Immersion
After Completion of
Release Experiments

44
Rhodamine B Release Profiles from Nanofibers
Nylon 6 Nanofibers Soy Protein/Nylon 6
Nanofibers
Soy Protein/PVA
Nanofibers
Soy Protein/Nylon 6
Soy Protein/Nylon 6
Core/Shell
Soy Protein/Nylon 6
Nanofibers
Core/Shell
Soy Protein/Nylon 6
+5 wt% PEG
Nanofibers

The Release Kinetics for the
Desorption-Limited Mechanism
Gt is the amount of dye/drug release by time t;
α=Msd0/(Msd0+Mbd0) is the nanoporosity factor;
Msd0 is the initial amount of dye/drug at the nanopore surface;
Mbd0 is the initial amount of dye/drug in the fiber bulk;
τr is the characteristic time for the release process.
45
• Srikar, R., Yarin, A. L., Megaridis, C. M., Bazilevsky, A. V., Kelly, E., 2008, Langmuir 24, 965-974.

Experimental Rhodamine B Release Profiles
vs. Predictions of the Desorption-Limited Theory
46
Nanofibers
Soy Protein/PVA
Nanofibers
Soy Protein/Nylon 6
Soy Protein/Nylon 6
Core/Shell
Soy Protein/Nylon 6
Nanofibers
Core/Shell
Soy Protein/Nylon 6
+5 wt% PEG
Nanofibers

α1 and τr1 correspond to drug release from the existing pores, and α2 and τr2 correspond to the “release”
of a leachable component of the fibers and thus, to drug release from the surfaces of the newly formed pores.
Gt is the amount of dye released by time t.
τr is the characteristic time of the release process.
The Release Kinetics for the Two-Stage
Desorption-Limited Mechanism
47

Experimental Rhodamine B Release Profiles
vs. Two-Stage Desorption-Limited Mechanism
48
Nanofibers
Soy Protein/PVA
Nanofibers
Soy Protein/Nylon 6
Soy Protein/Nylon 6
Core/Shell
Soy Protein/Nylon 6
Nanofibers
Core/Shell
Soy Protein/Nylon 6
+5 wt% PEG
Nanofibers

49
Sample
Average
α1(%)
Average
τr1(min)
Average
α2(%)
Average
τr2(min)
Average
E1(kJ/mol)
Average
E2(kJ/mol)
Monolithic
Nylon 6 38.21±5.63 15.05±2.35 20.17±3.72 299.15±97.95 28.43±0.38 35.79±0.6
SP/Nylon 49.23±7.22 23.4±3.46 10.79±3.09 199.31±40.66 29.53±0.38 34.85±0.26
SP/Nylon+5%PEG 66.52±3.84 20.55±1.46 15.19±1.24 191.58±25.17 29.23±0.17 34.78±0.1
SP/Nylon+10%PEG 56.8±1.63 38.37±6.56 36.77±1.31 490.29±180.73 30.75±0.45 37.59±0.04
Core/Shell
SP/Nylon 36.98±0.84 20.96±2.71 15.66±2.72 362.07±14.04 29.26±0.31 36.39±+0.02
SP/Nylon+5%PEG 38.4±3.98 13.67±9.88 19.38±1.16 396.03±182.93 25.13±5.6 36.31±1.55
SP/Nylon+10%PEG 30.41±4.34 20.2±7.21 33.94±3.52 607.20±132.24 29±1.01 37.61±0.34
Two-Stage Desorption-Limited
Mechanism Parameters

Pruned Vines Affected by Esca Fungi
Western Farm Press, July 1, 2017;
http://www.westernfarmpress.com/grapes/grapevine-canker-disease
-impacts-california-vineyards

Protection of Pruned Vines from Esca Fungi

Electrospun Biopolymer Membranes for Protection of Pruned Vines from Esca Fungi
S. Sett, M.W. Lee, M. Weith, B. Pourdeyhimi, A.L. YarinJ. Materials Chem. B 3,
2147-2162 (2015).

Protection of Pruned Vines from Esca Fungi
Rayon/soy protein/PCL nanofiber membranes;
The scale bars are 25 µm.

Delamination and Adhesion
(a) 180º peeling test of samples using Instron machine. (b) Dead weight test.

Prevention of Mold Invasion by Lignin/PCL Nanofibers
S. An et al. Cellulose 24, 951-965
(2017).

Photographs of the four molds tested, which correspond to Aspergillus versicola
KUC5201, Cladosporium cladosporioides KUC1385, Penicillium brevicompactum
KUC1819, and Trichoderma viride KUC5062, respectively.

Photographs of the LPNM-wrapped
specimens (a) at the beginning
and (b) after two weeks of mold
cultivation.
(c) Optical image
and (d, e) SEM images of the surface
of the tested LPNM.
The first, second, and third columns
correspond to tdep = 3, 6, and 9 h cases,
respectively.

Antibacterial (anti- E. coli) Action of
Silver-Decorated Soy Protein Nanofibers
Y. Zhang et al. Catalysis Communications 34, 35-40 (2013).

Heavy Metal Ion Adsorption on Nano-Textured
Biopolymer Membranes
A. Kolbasov, S. Sinha-Ray, A.L. Yarin, B. Pourdeyhimi. J. Membrane Sci. 530, 250-263
(2017).

Heavy Metal Ion Adsorption on Nano-Textured
Biopolymer Membranes
Macroscopic and microscopic images of:
(a,b) lignin/nylon-6 membrane;
(c,d) oats/nylon-6 membrane; (e,f) sodium alginate/PVA membrane;
(g,h) soy protein/nylon-6 membrane; and (i,j) chitosan/nylon-6 membrane.

Lead Adsorption on Nano-Textured Biopolymer Membranes in Throughflow

Heavy Metal Adsorption on Biopolymer Nanofiber
Membranes in Throughflow: Theory
2
2
c c c
Pe Da c
t x x
∂ ∂ ∂
+ = − × θ
∂ ∂ ∂
(1)
Da c
t
∂θ
=− × θ
∂
(2)
where Pe and Da are the dimensionless Peclet and Damkohler numbers, respectively,
v
Pe
D
=

(3)
2
k
Da
D
=

(4)
The boundary conditions at t>0 are imposed as following
c
x 0, c 1; x 1, 0
x
∂
= = = =
∂
(5)
The initial conditions at t=0 are imposed as
c 1, 1= θ= (6)

Heavy Metal Adsorption on Biopolymer Nanofiber
Membranes in Throughflow: Theory vs. Experiment
(a,b) lignin- and (c,d) oats-containing nano-textured membranes.

Heavy Metal Adsorption on Commerical Adsorbents
and Biopolymer Nanofiber Membranes: Comparative
Efficiency
Adsorbent
Pb
(mg/g)
Price ($/Metric
Ton)
TiO2 81.3 1000-3000
Modified AlO3 100
ZnO 6.7 2000-2500
CeO2 9.2
Activated carbon 26.5 1000-2000
Lignin-containing
nanofibers
37
Oat-containing
nanofibers
11

Book Containing Multiple Details on Our Work Published by Cambridge University
Press in 2014

Conclusion
• Solution blowing is an economically feasible and industrially scalable method for
producing nanofibers from bio-waste.
• Mechanical and the adhesion characteristics are appropriate for a number of
important applications.
• Nanofibers can be formed from a wide range of plant- and animal-derived biopolymers.
• Bio-waste-derived nano-textured membranes hold great promise for such
biomedical applications as controlled drug delivery, protection of pruned plants from fungi
invasion, protection of pine sapwood from mold invasion, and anti-bacterial action.
• Nano-textured membranes solution blown from bio-waste hold great promise
as adsorbents for removal of heavy metal ions from polluted water and are competitive
with commercial adsorbents.
• As by-products of biodiesel production and many other industrial processes,
green nano-textured materials derived from bio-waste can dramatically
increase sustainability. 70

Green nano-textured materials
can become such great scorers
as Pele!
71

Mechanical Properties of Biopolymer-Based Nanofibers

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