Downloaded via UNIV OF WASHINGTON on November 8, 2020 at 22:48:00 (UTC).
See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

www.acsami.org

Research Article

Field-Assisted Alignment of Cellulose Nanoﬁbrils in a Continuous
Flow-Focusing System
Heather G. Wise, Hidemasa Takana, Fumio Ohuchi, and Anthony B. Dichiara*
Cite This: ACS Appl. Mater. Interfaces 2020, 12, 28568−28575

ACCESS

Metrics & More

Read Online

Article Recommendations

sı Supporting Information*

ABSTRACT: The continuous production of macroscale ﬁlaments of 17 μm in diametercomprising aligned TEMPO-oxidized cellulose nanoﬁbrils (CNFs) is conducted using a ﬁeldassisted ﬂow-focusing process. The eﬀect of an AC external ﬁeld on the material’s structure
becomes signiﬁcant at a certain voltage, beyond which augmentations of the CNF orientation
factor up to 16% are obtained. Results indicate that the electric ﬁeld signiﬁcantly contributes toimprove the CNF ordering in the bulk, while the CNF alignment on the ﬁlament surface is only
slightly aﬀected by the applied voltage. X-ray diﬀraction shows that CNFs are densely packed
anisotropically in the plane parallel to the ﬁlament axis without any preferential out of planeorientation. The improved nanoscale ordering combined with the tight CNF packing yields
impressive enhancements in mechanical properties, with stiﬀness up to 25 GPa and more than
63% (up to 260 MPa), 46% (up to 2.8%), and 120% (up to 4.7 kJ/m3) increase in tensile
strength, strain-to-failure, and toughness, respectively. This study demonstrates for the ﬁrst time
the control over the structural ordering of anisotropic nanoparticles in a dynamic system using anelectric ﬁeld, which can have important implications for the development of sustainable
alternatives to synthetic textiles.
KEYWORDS: nanoﬁbrillated cellulose, nanoparticle orientation, ﬂow focusing, electric ﬁeld, renewable materials, mechanical properties■

DC electric ﬁelds are applied.29 When exposed to the ACelectric ﬁeld, individual CNFs rotate and align along the ﬁeld
direction if their movement is not restricted by thesurrounding environment.3 This is attributed to the anisotropic
nature of the material, which ensures that the dipole momentin the direction parallel to the CNF main axis is stronger thanthe one in the perpendicular direction. After rotation, interﬁbril
interactions take place to form cellulosic chains parallel to theelectric ﬁeld lines, which become thicker and longer as theelectric ﬁeld is applied for longer period of time. Some reports
examined how the parameters of the applied electric ﬁeld (i.e.,
amplitude, duration, etc.) inﬂuence the orientation of CNFs invarious solutions,3,27 while other researchers used a combination of shear forces and an electric ﬁeld to improve
nanocellulose alignment.30 However, all these studies arelimited to the preparation of thin ﬁlms in batch experiments.
To the best of our knowledge, there is no report in theliterature where an AC electric ﬁeld has been applied in acontinuous ﬂow system to control the nanoscale orientation ofelongated particles.

INTRODUCTION
Cellulose nanoﬁbrils (CNFs) are a class of earth-abundantbiobased and biocompatible materials with attractive properties such as lightweight, thermal stability, and good strength.1
When assembled into macroscale materials, the mechanicaland dielectric performances of the resulting components arestrongly inﬂuenced by the CNF orientation in these systems.2,3The development of highly ordered structures comprisingcellulose-based nanomaterials with a high aspect ratio has
recently spurred great interest.4 In this context, multiple
techniques for controlling the collective alignment of colloidal
nanocellulose have been explored and can be divided into two
categories depending on what type of external forces are used
to impose alignment. Typical external forces involve
mechanical stretching, 5−8 electric ﬁelds, 9−11 magnetic
ﬁelds,12−14 and liquid shear ﬂow focusing,15−19 while thetendency of certain particles to self-assemble into orderedstructures can be exploited in some cases without the need forexternal forces.20 Although electromagnetic applications havebeen widely used to align various elongated nanoparticles,21−23
including cellulose nanocrystals,10,24−26 studies focusing on
nanoﬁbrillated cellulose remain relatively scarce.3,27 Amongthese methods, only the use of an AC electric ﬁeld appears tobe versatile enough for practical implementation. This isbecause the low magnetic susceptibility of cellulose requires
unrealistically strong magnetic ﬁelds,28 while the negative
charges of CNF tend to generate aggregates at the anode when
© 2020 American Chemical Society

Received: April 20, 2020
Accepted: May 26, 2020
Published: May 26, 2020

28568

https://dx.doi.org/10.1021/acsami.0c07272
ACS Appl. Mater. Interfaces 2020, 12, 28568−28575

ACS Applied Materials & Interfaces

www.acsami.org

Research Article

Figure 1. Assembly of nanostructured cellulosic ﬁlaments. (A) Schematic of the ﬁeld-assisted double-ﬂow-focusing channel used for the preparationof macroscopic ﬁlaments. The CNF suspension is injected in the core ﬂow, while DI water and acid at low pH are supplied in the ﬁrst and second
extensional ﬂows, respectively. (B) Optical microscope image of the double-ﬂow-focusing part of the setup represented horizontally. Note that bluedyes were added to the core ﬂow for clarity purposes. (C) Polarized optical transmission measurements of CNF alignment at various applied
voltages along the core microﬂuidic channel, as illustrated in the above schematic.

amplitude of the AC electric ﬁeld inﬂuences the mechanicalproperties of the resulting nanocomposites.

One of the main challenges of using an AC external ﬁeld in a
dynamic process consists of locking the ﬁeld-aligned CNFs
into a metastable structure as the materials travel through theelectric ﬁeld to prevent the time dependent relaxation toward
isotropy due to Brownian diﬀusion. Inspired by the ﬂowfocusing approach,31 the present study employs a set ofextensional ﬂows downstream to initiate a sol−gel transition
before Brownian motion becomes dominant, hence forming
highly ordered cellulose ﬁlaments. While the hydrodynamicalignment may induce nonuniform orientation proﬁles acrossthe ﬁber width due to the inherent velocity gradient toward thechannel walls,32 the utilization of an AC electric ﬁeld may help
to mitigate this issue for the production of anisotropic anduniform ﬁbers with larger diameters.
In this research, TEMPO-oxidized CNFs were extracted
from renewable softwood pulp to produce anisotropic ﬁbers
using an innovative ﬁeld-assisted ﬂow-focusing process. The
continuous production of renewable ﬁbers with goodmechanical attributes is particularly relevant considering thatﬁbers account for more than 20% of the overall plastic
production, which was valued at $55 trillion in 2017.33 The
evolution of CNF alignment during processing with regard to
the applied voltage was studied in situ using polarized optical
microscopy. Both surface and bulk order characterizations of
the resulting ﬁlaments were conducted, respectively, by
scanning electron microscopy coupled with image analysis
and by orientation dependent variation of the polarized Raman
scattering signal. 2D-XRD was performed to examine the CNF
orientation in the planes perpendicular and parallel to theﬁlament axis. Finally, several meters of ﬁlaments were
produced under diﬀerent conditions to investigate how the■

RESULTS AND DISCUSSION
CNFs were synthesized on the basis of a previously reported
TEMPO-mediated oxidation procedure with 3 mmol of
NaClO per gram of bleached softwood pulp, followed byhomogenization using mechanical blending and double
acoustic irradiation.34−37 As-prepared CNFs exhibited amean length and diameter of 650 and 2 nm, respectively,
yielding a high aspect ratio of 300 (Figure S1). Note that, forsimplicity purposes, this value considers the ﬁbers to be fully
stretched out, which is unlikely to be the case in aqueous
suspensions. The carboxylate content of CNFs was 0.7 mmol/g, as measured by conductometric titration (Figure S2), andthe crystallinity index was 41%, as determined by XRD
according to the Segal method (Figure S3).38 The CNFs werecompletely dispersed at the individual nanoﬁbril level in waterby electrostatic repulsion and osmotic eﬀects due to anionicallycharged carboxylate groups densely present onto the CNF
surface.39,40 Aqueous suspensions containing 0.3 wt % CNFs,
exhibiting a viscosity of 13 mPa·s, were fed into a 1 mm
microﬂuidic channel for the continuous fabrication of macroscopic cellulose ﬁlaments (Video S1). To align the CNFs inparallel with the ﬁlament axis, the core ﬂow was equipped with
4 mm circular electrodes vertically spaced every 14 mm, withthe electrode surface directly exposed to the CNF to generate
an alternating AC electric ﬁeld. Two extensional ﬂows were
installed downstream, with the ﬁrst one composed of waterand the second one comprising 1 M HCl, as illustrated in
Figure 1A. A combination of ﬁve syringe pumps were used to28569

https://dx.doi.org/10.1021/acsami.0c07272
ACS Appl. Mater. Interfaces 2020, 12, 28568−28575

ACS Applied Materials & Interfaces

www.acsami.org

Research Article

Figure 2. Morphological characterization of the prepared biobased ﬁlaments. (A) Representative SEM image of a cellulosic ﬁlament with thediameter distribution shown in the inset. (B) SEM image of the cross section of a ﬁlament showing a layered structure with dense CNF packing.
Histograms representing the orientation degree of CNF threads on the surface of macroscopic ﬁlaments prepared (C) without and (D) with an
external electric ﬁeld. High magniﬁcation SEM images of the ﬁlament surfaces are shown in the insets.

Besides assisting nanoparticle alignment by accelerating thecore ﬂow, the ﬁrst set of extensional ﬂows (i.e., position 1)
generated a protecting sheath ﬂow of DI water to prevent CNF
friction with the microﬂuidic channel wall. When 600 V wasapplied compared to the baseline experiment without an AC
external ﬁeld, the signal intensity increased by 44% and 56% at
the ﬁrst and second extensional ﬂow positions (i.e., channel
positions 1 and 5), respectively. Beyond the second set ofextensional ﬂows (i.e., position 5), the presence of low pH acidlimited electrostatic repulsions between individual CNFs dueto the protonation of carboxyl (COO−) groups and promoted
the sol−gel transition of the biopolymer, forming well-orderedmacroscopic ﬁlaments.31,41,42 These results reveal that the
upstream ﬁeld-assisted alignment of the core ﬂow oﬀers aunique opportunity to improve the downstream ordering of
nanoparticles induced by extensional ﬂows.
The continuous ﬁlaments made by the ﬁeld-assisted ﬂowfocusing process were cut into small sections and air-dried
under tension for further characterization. Electron microscopy
analysis revealed that all ﬁlaments exhibited similar ribbed
textures with a mean diameter of 17.7 ± 4.3 μm regardless of
the applied voltage (Figure 2A). The representative crosssection image of a ﬁlament in Figure 2B shows that CNFs weretightly packed into a well-deﬁned layered structure. This wasconsistent with the XRD pattern of macroscopic ﬁlaments(Figure S3), which was similar to that of CNFs with a much
lower intensity of cellulose peaks, suggesting a compact layoutof CNFs. Observations at higher magniﬁcations indicated that

control the ﬂow rates of the core and all extensional ﬂows,
which were kept constant for all experiments. Opticaltransmission measurements of the core ﬂow were collected
between crossed polarizers to examine the birefringent
properties of CNFs at diﬀerent positions along the microﬂuidic
channel. Experiments were conducted at diﬀerent applied
voltages varying from 0 to 600 V in 200 V increments. Voltages
higher than 600 V were not considered to prevent waterelectrolysis. The variations in signal intensity observed at
position 0 indicate that the sole electromagnetic polarization of
the core ﬂow gave rise to the nematic ordering of CNFs insolution, which gradually improved with increasing an applied
AC external ﬁeld. This means that the electrostatic torqueexerted on the CNFs by the applied voltage was suﬃcient toovercome the eﬀects of Brownian diﬀusion. It is also worth
noting that the CNF response to the electric ﬁeld was not
linear and started to level oﬀ at elevated voltages, which isconsistent with recent results from numerical simulations.15
The magnitude of the ﬁeld-assisted alignment at 600 V (i.e.,
signal intensity of 0.30) was only 25% lower than the nematic
CNF ordering obtained by the extensional ﬂows at position 1
when no voltage was applied (i.e., signal intensity of 0.37).
This demonstrates that polar moieties grafted on the CNF
surface during the TEMPO-mediated oxidation enable strong
CNF polarization and spontaneous alignment of dipoles under
an applied AC external ﬁeld. In addition, the beneﬁts of theﬁeld-assisted alignment are well maintained throughout theentire ﬂow-focusing process despite Brownian diﬀusion.
28570

https://dx.doi.org/10.1021/acsami.0c07272
ACS Appl. Mater. Interfaces 2020, 12, 28568−28575

ACS Applied Materials & Interfaces

www.acsami.org

each ﬁlament was composed of multiple CNF bundles of 1−3
μm in diameter forming aligned threads throughout theﬁlament.11 To assess the degree of alignment of thesestriations, the orientation index, fc, was computed on thebasis of eq S2 using ImageJ software.43 This microscaleorientation factor was determined for ﬁlaments prepared under
the same ﬂow conditions but at diﬀerent applied voltages. The
high ordering of CNF bundles was conﬁrmed by orientation
factors higher than 0.9 in each case. When an external electricﬁeld was applied (Figure 2D), the orientation index slightly
increased from 0.92 to 0.94 compared to the baseline ﬁlament
without applied voltage (Figure 2C). However, there were no
statistically signiﬁcant diﬀerences between the orientation
factors measured at various applied voltages.
While the above results provided an estimate of the
microscale directionality of CNFs on the external surface of
the ﬁlament, polarized Raman spectroscopy was conducted atambient conditions to better examine the bulk orientation andthe quality of the alignment of individual CNFs within theﬁlaments.44,45 Samples were mounted on silicon dioxidewafers, and all spectra were collected at an excitation
wavelength of 785 nm and normalized using the silicon
dioxide signature peak at 521 cm−1. The characteristic peak at
1095 cm−1, commonly associated with the C−O vibration of
the cellulose backbone parallel to the molecular chain
axis,46,47was studied due to its strong dependence on thepolarization angle.48 Since the Raman intensity of randomly
oriented ﬁbrils remains constant regardless of the polarization
angle, a systematic deviation from this can serve to characterize
the degree of ﬁbril alignment. Figure 3 shows that, when thechange in intensity indicates that greater optical anisotropy wasachieved when the applied voltage reached 600 V.
Furthermore, the absence of shift in the main cellulose peaks
revealed that the structural integrity of the ﬁlament waspreserved under applied voltages up to 600 V (Figure S4). The
combination of electron microscopy and image analysis withpolarized Raman spectroscopy revealed that an externallyapplied electric ﬁeld improved the alignment of CNFs both on
the ﬁlament surface and in the bulk. In the absence of an ACelectric ﬁeld, however, bulk ordering was signiﬁcantly reduced,
while surface ordering was only slightly aﬀected. This may be
attributed to the radial velocity proﬁle of CNFs from the core
ﬂow toward the channel walls.32 Besides enhancing to someextent the magnitude of CNF ordering, the utilization of an ACelectric ﬁeld ensures a more uniform CNF orientation acrossthe macroscale ﬁlament.
To evaluate the inﬂuence of the amplitude of the electricﬁeld on the CNF ordering, ﬁlaments prepared at diﬀerent
applied voltages were characterized by 2D-XRD (Figure 4).
The characteristic peak of the (200) crystallographic plane ofcellulose at 2θ = 22.4°, commonly attributed to the d spacing
between crystal regions of individual cellulose chains, was used
to assess the CNF orientation in the ﬁlaments.49,50 CNF
orientation was analyzed both in the planes perpendicular (Ψ)
and parallel (Φ) to the ﬁlament axis, as illustrated in Figure 4E.
Parts A−D of Figure 4 report the evolution of the (200) band
intensity as a function of the in-plane rotation angle forﬁlaments produced under diﬀerent conditions. Each specimen
exhibited two distinct peaks at 0° and 180°, revealing theuniaxial orientation of CNFs along the ﬁlament axis. Thesepeaks are obviously sharper in the case of the ﬁlaments
prepared at 600 V, while only minimal variations of the peaks’
full width half-maximum (fwhm) are observed for the othersamples. This was consistent with the short appearance rate ofthe (200) band in the diﬀractogram of the 600 V ﬁlamentcompared to the other samples. The orientation index, fc, wascomputed on the basis of eq S2 to quantify the quality of CNF
alignment in the diﬀerent ﬁlaments.31,7 Note that the slight
diﬀerences between the fc values determined at 0° and 180°
might be attributed to the diﬃculty of mounting perfectly
stretched ﬁlaments onto the XRD stage. The averages between
the fc values calculated at 0° and 180° were considered forcomparison purposes. The fc values followed an upward trend
and slightly increased from 0.815 to 0.865 when the applied
voltage increased from 0 up to 400 V. Beyond this point, the fc
culminated to 0.945 at 600 V, representing a 16% increase
from the baseline ﬁlament synthesized without an AC externalﬁeld. These results reveal that, while the addition of an external
electric ﬁeld can improve CNF ordering, its eﬀects become
signiﬁcant once a threshold voltage is applied to the corechannel of the ﬂow-focusing setup. This is consistent withprevious batch experiments where no obvious alignment wasobserved in nanocellulose samples exposed to an electric ﬁeld
lower than a certain value.24 In the out-of-plane direction(Figure 4F), however, the (200) band remained clearly visible
in each diﬀractogram when the ﬁlaments were tilted from 0° to
90° without any obvious diﬀerences between ﬁlaments
prepared at various applied voltages. This indicates theabsence of preferential out-of-plane CNF orientation, suggesting that the CNFs were packed isotropically in-the-plane, Ψ,but parallel to the plane, Φ.
The inﬂuence of CNF orientation with respect to applied
voltages on the mechanical response of the ﬁlaments was

Figure 3. Raman spectra of cellulosic ﬁlaments prepared with (red)and without (black) an external electric ﬁeld. The voltage applied inthis case was 600 V. Each spectra was collected at an excitation
wavelength of 785 nm in parallel with (solid line) and perpendicularto (dashed line) the ﬁlament axis.

long axis of the ﬁlament was parallel to the incident laser
polarization (//), a large enhancement of the Raman intensity
was observed for all specimens. Rotating the ﬁlaments from 0°
to 90° reduced the intensity of the 1095 cm−1 band more
dramatically for the ﬁlament prepared with the assistance of an
external electric ﬁeld. The ﬁlaments produced under applied
voltage retained only 15.6% of their maximum intensity, while
the ﬁlaments synthesized without an AC external ﬁeld retained
more than 30% of their maximum intensity. This signiﬁcant
28571

Research Article

https://dx.doi.org/10.1021/acsami.0c07272
ACS Appl. Mater. Interfaces 2020, 12, 28568−28575

ACS Applied Materials & Interfaces

www.acsami.org

Research Article

Figure 4. 2D XRD analysis of CNF alignment within the cellulosic ﬁlaments. (A) Azimuthal integration of the (200) scattering plane of thediﬀractograms with respect to Φ rotations for cellulosic ﬁlaments prepared at (A) 0, (B) 200, (C) 400, and (D) 600 V. (E) Schematic illustrating
the axis of rotations with respect to the ﬁlament layout on the XRD stage for the in-plane, Φ, and out-of-plane, Ψ, directions. (F) Diﬀractograms ofcellulosic ﬁlaments prepared at various applied voltages with respect to Ψ rotations.

Figure 5. Mechanical properties of cellulosic ﬁlaments. (A) Bar graph showing the ultimate tensile strength, strain-to-failure, and Young’s modulus
of ﬁlaments prepared at diﬀerent applied voltage. (B) Triplicate stress−strain curves of representative ﬁlaments prepared at 0 (black) and 600 V(red).

evaluated using stress−strain measurements. One meter longﬁlaments were prepared at various applied voltages and were
cut into 3 cm long sections. For statistical soundness, over 30
tensile tests were conducted for each condition and the results
were subjected to one-way analysis of variance (ANOVA) andTukey tests based on a 5% α level (i.e., 95% conﬁdence).

Statistical signiﬁcance in tensile strength, strain-to-failure, andtoughness were determined with p-values <0.05. As shown in
Figure 5A, the tensile strength and strain-to-failure for theﬁlaments prepared at 600 V were signiﬁcantly larger than thosefor the others samples. This was consistent with the XRD data
since the largest orientation enhancements were expected to28572

https://dx.doi.org/10.1021/acsami.0c07272
ACS Appl. Mater. Interfaces 2020, 12, 28568−28575

ACS Applied Materials & Interfaces

www.acsami.org

yield the greatest eﬀects on the mechanical properties.
Compared to the baseline ﬁlaments made without an electric
ﬁeld, the ﬁlaments at 600 V exhibited more than 63% and 46%
augmentations in tensile strength and strain-to-failure,
respectively. Such simultaneous increases in both tensile
strength and strain-to-failure at 600 V yielded an impressive
improvement of the material’s toughness, with nearly 120%augmentation compared to the baseline ﬁlament preparedwithout an AC external ﬁeld. It is noteworthy that this increase
in toughness did not sacriﬁce the material’s stiﬀness, as changes
in the ﬁlaments’ modulus of elasticity were not statisticallysigniﬁcant. The Young’s modulus hovered around 20 GPa,
which is among the highest values reported for biobasedmaterials.32,51−53 In addition, the yield point, delineating theregion when the material begins to deform plastically, wasraised drastically when the applied voltage increased from 0 to
600 V, as depicted in Figure 5B. This reveals that important
improvements in mechanical resilience can be achieved forstructural materials with highly ordered nanoﬁbrils. The goodmechanical properties obtained at elevated voltages can be
attributed to the anisotropic nature of the ﬁlaments combinedwith the tight CNF packing and limited electric ﬁeld-induced
structural defects.

Discussions of CNF preparation and characterization,
charge density of CNF dispersions, 2D X-ray diﬀraction,and ﬁber formation and characterization and ﬁgures ofhistograms, AFM images, plot of mixtures representing
diﬀerent aspects of the CNF synthetic process, intensityof ﬁlms, and Raman spectroscopy (PDF)
Video of running microﬂudic channel (AVI)■AUTHOR INFORMATION

Corresponding Author

Anthony B. Dichiara − School of Environmental & Forest
Sciences, University of Washington, Seattle 98195, UnitedStates; orcid.org/0000-0002-3118-7029;
Email: abdichia@uw.edu

Authors

Heather G. Wise − School of Environmental & Forest Sciences,
University of Washington, Seattle 98195, United States;
orcid.org/0000-0002-7627-1048
Hidemasa Takana − Insititue of Fluid Science, Tohoku
University, Sendai 980-8577, Japan
Fumio Ohuchi − Material Science & Engineering Department,
University of Washington, Seattle 98195, United States
Complete contact information is available at:https://pubs.acs.org/10.1021/acsami.0c07272■

CONCLUSION
In summary, macroscopic ﬁlaments comprising highly ordered
TEMPO-oxidized CNFs were produced from renewable wood
pulp using an innovative ﬁeld-assisted ﬂow-focusing process.
Polar moieties on the CNF surface enabled strong polarizationand spontaneous alignment of dipoles under an appliedexternal electric ﬁeld, which signiﬁcantly improved thedownstream nematic ordering of CNFs despite diﬀusioncaused by Brownian motion. While the upstream ﬁeld-assistedalignment enhanced the CNF ordering both on the ﬁlament
surface and in the bulk, its eﬀect became dominant once a
threshold voltage was applied. Filaments produced at 600 V
had greater optical anisotropy and exhibited a 16%
augmentation in orientation index compared to ﬁlaments
prepared without an AC external ﬁeld. Despite the relatively
high voltages that incurred, there were no signs of either
electric ﬁeld-induced structural defects or water electrolysis.
2D XRD analysis also revealed that the CNFs were randomlyaligned in the plane along the ﬁlament length but oriented
parallel to the ﬁlament axis. The high orientation degree of
CNFs combined with their dense packing yielded impressive
improvements in the mechanical properties of the resulting
ﬁlaments, with up to 120% increase in toughness withoutcompromising the material’s stiﬀness. These results demonstrate for the ﬁrst time that an external electric ﬁeld can beapplied in a continuous ﬂow process to control the structuralordering of anisotropic materials. Future optimization of thebiobased ﬁlaments can be made possible through thefunctionalization of CNFs with charged molecules and/or
magnetic nanoparticles to tune the material response to anelectromagnetic ﬁeld and adjust interparticle interactions for
multifunctional applications.

■

Research Article

Notes

The authors declare no competing ﬁnancial interest.

■

ACKNOWLEDGMENTS
This research was supported by the McIntire-Stennis
Cooperative Forestry Research Program (grant#
NI19MSCFRXXXG035, project accession# 1020630) fromthe USDA National Institute of Food and Agriculture and by
the JSPS Kakenhi Program (grant# 19K04187). The present
work was carried out under the University of WashingtonTohoku University: Academic Open Space and under the
Collaborative Research Project of the Institute of Fluid
Science, Tohoku University. The authors would like toacknowledge Mr. Ken Fukumori for his assistance with theﬁlament preparation and Mr. Justin Niles for contributions tothe cover art.

■

REFERENCES(1) Tayeb, A. H.; Amini, E.; Ghasemi, S.; Tajvidi, M. Cellulose
NanomaterialsBinding Properties and Applications: A Review.
Molecules 2018, 23 (10), 2684.
(2) Mohammadi, P.; Toivonen, M. S.; Ikkala, O.; Wagermaier, W.;
Linder, M. B. Aligning Cellulose Nanofibril Dispersions for Tougher
Fibers. Sci. Rep. 2017, 7 (1), 1−10.
(3) Kadimi, A.; Benhamou, K.; Ounaies, Z.; Magnin, A.; Dufresne,A.; Kaddami, H.; Raihane, M. Electric Field Alignment of Nanofibrillated Cellulose (NFC) in Silicone Oil: Impact on Electrical
Properties. ACS Appl. Mater. Interfaces 2014, 6 (12), 9418−9425.
(4) Zhu, Q.; Yao, Q.; Sun, J.; Chen, H.; Xu, W.; Liu, J.; Wang, Q.
Stimuli Induced Cellulose Nanomaterials Alignment and Its Emerging
Applications: A Review. Carbohydr. Polym. 2020, 230, 115609.
(5) Reising, A. B.; Moon, R. J.; Youngblood, J. P. Effect of Particle
Alignment on Mechanical Properties of Neat Cellulose Nanocrystal
Films. Journal of Science & Technology for Forest Products and Processes
2012, 2 (6), 32−41.
(6) Fall, A. B.; Lindström, S. B.; Sprakel, J.; Wågberg, L. A Physical
Cross-Linking Process of Cellulose Nanofibril Gels with ShearControlled Fibril Orientation. Soft Matter 2013, 9 (6), 1852−1863.

ASSOCIATED CONTENT* Supporting Information
sı

The Supporting Information is available free of charge athttps://pubs.acs.org/doi/10.1021/acsami.0c07272.
28573

https://dx.doi.org/10.1021/acsami.0c07272
ACS Appl. Mater. Interfaces 2020, 12, 28568−28575

ACS Applied Materials & Interfaces

www.acsami.org(7) Tang, H.; Butchosa, N.; Zhou, Q. A Transparent, Hazy, andStrong Macroscopic Ribbon of Oriented Cellulose Nanofibrils
Bearing Poly(Ethylene Glycol). Adv. Mater. 2015, 27 (12), 2070−
2076.
(8) Kafy, A.; Kim, H. C.; Zhai, L.; Kim, J. W.; Hai, L. V.; Kang, T. J.;
kim, J. Cellulose Long Fibers Fabricated from Cellulose Nanofibers
and Its Strong and Tough Characteristics. Sci. Rep. 2017, 7, 1.
(9) Kadimi, A.; Benhamou, K.; Habibi, Y.; Ounaies, Z.; Kaddami, H.
Nanocellulose Alignment and Electrical Properties Improvement. In
Multifunctional Polymeric Nanocomposites Based on Cellulosic Reinforcements; Puglia, D., Fortunati, E., Kenny, J. M., Eds.; William Andrew
Publishing, 2016; pp 343−376. .
(10) Bordel, D.; Putaux, J.-L.; Heux, L. Orientation of Native
Cellulose in an Electric Field. Langmuir 2006, 22 (11), 4899−4901.
(11) Choi, K.; Gao, C. Y.; Nam, J. D.; Choi, H. J. Cellulose-Based
Smart Fluids under Applied Electric Fields. Materials 2017, 10 (9),1060.
(12) Kim, H. C.; Kang, J.; Park, J. H.; Akther, A.; Kim, J. Feasibility
Study of Cellulose Nanoﬁber Alignment by High DC Magnetic Field.
Nanosensors, Biosensors, Info-Tech Sensors and 3D Systems 2017;
International Society for Optics and Photonics, 2017; Vol. 10167, p
101670H. .
(13) Sugiyama, J.; Chanzy, H.; Maret, G. Orientation of Cellulose
Microcrystals by Strong Magnetic Fields. Macromolecules 1992, 25(16), 4232−4234.
(14) Pullawan, T.; Wilkinson, A. N.; Eichhorn, S. J. Influence ofMagnetic Field Alignment of Cellulose Whiskers on the Mechanics of
All-Cellulose Nanocomposites. Biomacromolecules 2012, 13 (8),2528−2536.
(15) Takana, H.; Guo, M. Numerical Simulation on Electrostatic
Alignment Control of Cellulose Nano-Fibrils in Flow. Nanotechnology
2020, 31, 205602.
(16) Smith, D. E.; Babcock, H. P.; Chu, S. Single-Polymer Dynamics
in Steady Shear Flow. Science 1999, 283 (5408), 1724−1727.
(17) Lundahl, M. J.; Klar, V.; Wang, L.; Ago, M.; Rojas, O. J.
Spinning of Cellulose Nanofibrils into Filaments: A Review. Ind. Eng.
Chem. Res. 2017, 56 (1), 8−19.
(18) Clemons, C. Nanocellulose in Spun Continuous Fibers: A
Review and Future Outlook. J. Renewable Mater. 2016, 4 (5), 327−
339.
(19) Nechyporchuk, O.; Håkansson, K. M. O.; Gowda, V. K.;
Lundell, F.; Hagström, B.; Köhnke, T. Continuous Assembly of
Cellulose Nanofibrils and Nanocrystals into Strong Macrofibers
through Microfluidic Spinning. Advanced Materials Technologies 2019,
4 (2), 1800557.
(20) Mredha, M. T. I.; Le, H. H.; Tran, V. T.; Trtik, P.; Cui, J.; Jeon,
I. Anisotropic Tough Multilayer Hydrogels with Programmable
Orientation. Mater. Horiz. 2019, 6 (7), 1504−1511.
(21) Gupta, P.; Rajput, M.; Singla, N.; Kumar, V.; Lahiri, D. Electric
Field and Current Assisted Alignment of CNT inside Polymer Matrix
and Its Effects on Electrical and Mechanical Properties. Polymer 2016,
89, 119−127.
(22) Oliva-Avilés, A. I.; Avilés, F.; Sosa, V.; Oliva, A. I.; Gamboa, F.
Dynamics of Carbon Nanotube Alignment by Electric Fields.
Nanotechnology 2012, 23 (46), 465710.
(23) Chen, X. Q.; Saito, T.; Yamada, H.; Matsushige, K. Aligning
Single-Wall Carbon Nanotubes with an Alternating-Current Electric
Field. Appl. Phys. Lett. 2001, 78 (23), 3714−3716.
(24) Habibi, Y.; Heim, T.; Douillard, R. AC Electric Field-Assisted
Assembly and Alignment of Cellulose Nanocrystals. J. Polym. Sci., Part
B: Polym. Phys. 2008, 46 (14), 1430.
(25) Kalidindi, S.; Ounaies, Z.; Kaddami, H. Toward the Preparationof Nanocomposites with Oriented Fillers: Electric Field-Manipulationof Cellulose Whiskers in Silicone Oil. Smart Mater. Struct. 2010, 19(9), No. 094002.
(26) Aguié-Béghin, V.; Molinari, M.; Hambardzumyan, A.; Foulon,
L.; Habibi, Y.; Heim, T.; Blossey, R.; Douillard, R. Preparation ofOrdered Films of Cellulose Nanocrystals. Model Cellulosic Surfaces;

ACS Symposium Series; American Chemical Society, 2009; Vol.
1019, pp 115−136. .
(27) Xu, S.; Liu, D.; Zhang, Q.; Fu, Q. Electric Field-Induced
Alignment of Nanofibrillated Cellulose in Thermoplastic Polyurethane Matrix. Compos. Sci. Technol. 2018, 156, 117−126.
(28) Tatsumi, M.; Kimura, F.; Kimura, T.; Teramoto, Y.; Nishio, Y.
Anisotropic Polymer Composites Synthesized by Immobilizing
Cellulose Nanocrystal Suspensions Specifically Oriented under
Magnetic Fields. Biomacromolecules 2014, 15 (12), 4579−4589.
(29) Ten, E.; Jiang, L.; Wolcott, M. P. Preparation and Properties of
Aligned Poly(3-Hydroxybutyrate-Co-3-Hydroxyvalerate)/Cellulose
Nanowhiskers Composites. Carbohydr. Polym. 2013, 92 (1), 206−
213.
(30) Csoka, L.; Hoeger, I. C.; Peralta, P.; Peszlen, I.; Rojas, O. J.
Dielectrophoresis of Cellulose Nanocrystals and Alignment in
Ultrathin Films by Electric Field-Assisted Shear Assembly. J. Colloid
Interface Sci. 2011, 363 (1), 206−212.
(31) Mittal, N.; Ansari, F.; Gowda, V. K.; Brouzet, C.; Chen, P.;
Larsson, P. T.; Roth, S. V.; Lundell, F.; Wågberg, L.; Kotov, N. A.;
Söderberg, L. D. Multiscale Control of Nanocellulose Assembly:
Transferring Remarkable Nanoscale Fibril Mechanics to Macroscale
Fibers. ACS Nano 2018, 12 (7), 6378−6388.
(32) Håkansson, K. M. O.; Fall, A. B.; Lundell, F.; Yu, S.; Krywka,
C.; Roth, S. V.; Santoro, G.; Kvick, M.; Prahl Wittberg, L.; Wågberg,
L.; Söderberg, L. D. Hydrodynamic Alignment and Assembly of
Nanofibrils Resulting in Strong Cellulose Filaments. Nat. Commun.
2014, 5, 4018.
(33) Lebreton, L. C. M.; van der Zwet, J.; Damsteeg, J.-W.; Slat, B.;
Andrady, A.; Reisser, J. River Plastic Emissions to the World’s Oceans.
Nat. Commun. 2017, 8 (1), 1−10.
(34) Goodman, S. M.; Ferguson, N.; Dichiara, A. B. Lignin-Assisted
Double Acoustic Irradiation for Concentrated Aqueous Dispersions ofCarbon Nanotubes. RSC Adv. 2017, 7 (9), 5488−5496.
(35) Isogai, A.; Saito, T.; Fukuzumi, H. TEMPO-Oxidized Cellulose
Nanofibers. Nanoscale 2011, 3 (1), 71−85.
(36) Gu, J.; Hu, C.; Zhang, W.; Dichiara, A. B. Reagentless
Preparation of Shape Memory Cellulose Nanofibril Aerogels
Decorated with Pd Nanoparticles and Their Application in Dye
Discoloration. Appl. Catal., B 2018, 237, 482−490.
(37) Rattaz, A.; Mishra, S. P.; Chabot, B.; Daneault, C. Cellulose
Nanofibres by Sonocatalysed-TEMPO-Oxidation. Cellulose 2011, 18(3), 585.
(38) Segal, L.; Creely, J. J.; Martin, A. E.; Conrad, C. M. An
Empirical Method for Estimating the Degree of Crystallinity of Native
Cellulose Using the X-Ray Diffractometer. Text. Res. J. 1959, 29 (10),786−794.
(39) Fall, A. B.; Lindström, S. B.; Sundman, O.; Ö dberg, L.;Wågberg, L. Colloidal Stability of Aqueous Nanofibrillated Cellulose
Dispersions. Langmuir 2011, 27 (18), 11332−11338.
(40) Gu, J.; Dichiara, A. Hybridization between Cellulose Nanofibrils and Faceted Silver Nanoparticles Used with Surface Enhanced
Raman Scattering for Trace Dye Detection. Int. J. Biol. Macromol.
2020, 143, 85−92.
(41) Nishiyama, Y. Molecular Interactions in Nanocellulose
Assembly. Philos. Trans. R. Soc., A 2018, 376 (2112), 20170047.
(42) Nascimento, D. M.; Nunes, Y. L.; Figueirêdo, M. C. B.; deAzeredo, H. M. C.; Aouada, F. A.; Feitosa, J. P. A.; Rosa, M. F.;
Dufresne, A. Nanocellulose Nanocomposite Hydrogels: Technological and Environmental Issues. Green Chem. 2018, 20 (11), 2428−
2448.
(43) Sydney Gladman, A.; Matsumoto, E. A.; Nuzzo, R. G.;
Mahadevan, L.; Lewis, J. A. Biomimetic 4D Printing. Nat. Mater.
2016, 15 (4), 413−418.
(44) Xu, Y.; Atrens, A. D.; Stokes, J. R. Liquid Crystal Hydroglass
Formed via Phase Separation of Nanocellulose Colloidal Rods. Soft
Matter 2019, 15 (8), 1716−1720.
(45) Alizadehgiashi, M.; Khabibullin, A.; Li, Y.; Prince, E.;
Abolhasani, M.; Kumacheva, E. Shear-Induced Alignment of
28574

Research Article

https://dx.doi.org/10.1021/acsami.0c07272
ACS Appl. Mater. Interfaces 2020, 12, 28568−28575

ACS Applied Materials & Interfaces

www.acsami.org

Research Article

Anisotropic Nanoparticles in a Single-Droplet Oscillatory Microfluidic
Platform. Langmuir 2018, 34 (1), 322−330.
(46) Gierlinger, N.; Schwanninger, M.; Reinecke, A.; Burgert, I.
Molecular Changes during Tensile Deformation of Single Wood
Fibers Followed by Raman Microscopy. Biomacromolecules 2006, 7(7), 2077−2081.
(47) Wiley, J. H.; Atalla, R. H. Band Assignments in the Raman
Spectra of Celluloses. Carbohydr. Res. 1987, 160, 113−129.
(48) Hsieh, Y.-C.; Yano, H.; Nogi, M.; Eichhorn, S. J. An Estimationof the Young’s Modulus of Bacterial Cellulose Filaments. Cellulose
2008, 15 (4), 507−513.
(49) Munier, P.; Gordeyeva, K.; Bergström, L.; Fall, A. B. DirectionalFreezing of Nanocellulose Dispersions Aligns the Rod-Like Particles
and Produces Low-Density and Robust Particle Networks. Biomacromolecules 2016, 17 (5), 1875−1881.
(50) Ureña-Benavides, E. E.; Kitchens, C. L. Wide-Angle X-Ray
Diffraction of Cellulose Nanocrystal−Alginate Nanocomposite Fibers.
Macromolecules 2011, 44 (9), 3478−3484.
(51) Hooshmand, S.; Aitomäki, Y.; Norberg, N.; Mathew, A. P.;
Oksman, K. Dry-Spun Single-Filament Fibers Comprising Solely
Cellulose Nanofibers from Bioresidue. ACS Appl. Mater. Interfaces
2015, 7 (23), 13022−13028.
(52) Henriksson, M.; Berglund, L. A.; Isaksson, P.; Lindström, T.;
Nishino, T. Cellulose Nanopaper Structures of High Toughness.
Biomacromolecules 2008, 9 (6), 1579−1585.
(53) Galland, S.; Berthold, F.; Prakobna, K.; Berglund, L. A.
Holocellulose Nanofibers of High Molar Mass and Small Diameter for
High-Strength Nanopaper. Biomacromolecules 2015, 16 (8), 2427−
2435.

28575

https://dx.doi.org/10.1021/acsami.0c07272
ACS Appl. Mater. Interfaces 2020, 12, 28568−28575