Skip to main content
NCBI home page
ACS AuthorChoice logoLink to ACS AuthorChoice
. 2022 Oct 21;16(11):18390–18397. doi: 10.1021/acsnano.2c06392

One-Pot Hierarchical Structuring of Nanocellulose by Electrophoretic Deposition

Takaaki Kasuga †,*, Tsuguyuki Saito ‡, Hirotaka Koga †, Masaya Nogi †
PMCID: PMC9706670  PMID: 36270629

Abstract

graphic file with name nn2c06392_0006.jpg

The orientation control and the formation of hierarchical structures of nanoscale components, such as bionanofibers and nanosheets, have attracted considerable research interest with the aim of achieving sophisticated functional materials. Herein, we report a simple and flexible strategy for constructing sophisticated hierarchical structures through electrophoretic and electrochemical deposition. Cellulose nanofibers (CNFs), which are used as model materials, are deposited on an anode in an aqueous dispersion and seamlessly oriented from horizontal to vertical relatively to the electrode by adjusting the applied voltage between the electrodes. The oriented CNF hydrogels not only exhibit anisotropic mechanical properties but also form complex orientations and hierarchical structures, such as cartilage- and plant stem-like configurations in response to electrode shape and applied voltage. This simple and flexible technique is expected to be applicable to various materials and contribute to a wide range of fields that include biomimicry, functional nanomaterials, and sustainable and functional moldings.

Keywords: nanocellulose, hydrogel, hierarchical structure, biomimicry, electrophoretic deposition, orientation control

In nature, various living organisms use nanoscale components, such as nanofibers, to realize hierarchical structures that are highly strong and functional. Nanofibers, which are composed of biopolymers (e.g., cellulose, chitin, and collagen), form hierarchical structures with controlled orientations in living organisms to realize various functions necessary for the maintenance of life and the prosperity of the species.1−5 Plants, for example, contain cellulose nanofibers (CNFs) that are hierarchically oriented and form lightweight and robust structures.1,2 The anisotropic drying and shrinking phenomenon (“hygroscopic movement”) induced by the hierarchically oriented CNF structures contributes to species reproduction.3,4 Moreover, the cartilage in our bodies is known to contain collagen nanofibers that have highly oriented structures and provide both surface lubrication and cushioning.1,5 Hence, controlling the orientation and hierarchical structures of nanoscale components is critical for sustainability in living organisms.

The ability to structurally control nanomaterials has attracted considerable research interest with the aim of achieving particular functions, such as those of biological tissue.6−21 Previously, typical orientation control methods (e.g., shearing,6,7 stretching,8,9 applying alternating electric10,11 and magnetic fields,12 3D printing,13−17 and directional freezing18−20) have been applied to aqueous dispersions of nanomaterials, including nanofibers and nanosheets. Among these, 3D printing is an effective method that enables orientation control and molding at the same time.13−17 Also, directional freezing has been attracting attention in recent years because of its ability to control orientation and structure on a multiscale.18−20 These methods have advantages in flexibility of application and have attracted attention from a wider range of fields than other orientation control methods. However, it is still difficult to simultaneously achieve multiaxial orientation control, multiscale structuring, and molding using a simple process.

In this regard, we developed an electrophoretic and electrochemical technique for the simple and flexible orientational and hierarchical structural control of nanoscale components. Recently, the electrophoretic deposition of CNFs,22−24 cellulose nanocrystals,25,26 and chitosan27 has been utilized as a coating or a film preparation method. However, existing reports have achieved random orientation or chiral nematic orientation via self-assembly. In this study, CNFs prepared by TEMPO oxidation, which are negatively charged in water, were used as model materials. CNFs were electrophoretically and electrochemically deposited on the anode surface in a horizontal, random, or vertical orientation that depended on the applied voltage. Orientation control was also effective for electrodes with complex geometries, with CNFs demonstrated to stack easily in differently orientated states. In addition, we demonstrated a wide range of application possibilities, including biomimicking hydrogels and CNF moldings.

Results and Discussion

TEMPO-oxidized CNFs were used as model materials in this study. Copper and graphite electrodes were placed at the bottom and top of an acrylic cell containing a 0.2 wt % CNF/water dispersion, respectively (Figure 1a). CNFs were deposited on the anode at the bottom of the cell in hydrogel form when an applied voltage of 1–40 V (current density: 0.1–5 mA/cm2, Figure S1) was applied between the electrodes; CNFs were deposited on the anode at the bottom of the cell in a hydrogel form. The following actions contribute to the deposition of CNFs: electrophoresis by the electric field between the electrodes and two typical electrochemical reactions at the electrode/dispersion interface, elution of the electrode metal, and electrolysis of water.22−24 It has been reported that when a voltage exceeding the theoretical decomposition voltage of water (∼1.23 V) is applied, e.g., 3 V or more, the dispersion near the anode becomes acidic because of the electrolysis of water.22−24 The deposition rate of CNFs increased with increasing applied voltage (Figure 1i–k). The increase in the deposition rate might be attributable to the increase in the electric field strength and the elution rate of copper ions from the anode as well as acidification due to the electrolysis of water.23,24 The formed hydrogel appeared turquoise, which is ascribable to the adsorption of Cu ions by the carboxy groups of the CNFs (Figure 1b–d, Figures S2, S3). Interestingly, the CNFs were fixed in horizontal and vertical orientations with respect to the anode surface at applied voltages of 1 and 40 V, respectively (Figure 1e, f, h, i, k, Figure S4), while a close to randomly oriented state was observed at intermediate voltage (i.e., 10 V, Figure 1e, g, j); this state transformed into the horizontally or vertically oriented state at lower or higher applied voltage, respectively (Figure 1e).

Figure 1.

Figure 1

Open in a new tab

(a) Formation of oriented CNF hydrogel on the anode by sandwiching a CNF/water dispersion between the anode and cathode and applying a DC voltage between them. Oriented CNF hydrogels prepared at applied voltages of (b) 1, (c) 10, and (d) 40 V. CNF orientations at various applied voltages were investigated by (e) wide-angle X-ray diffractometry (WAXD), (f–h) field-emission scanning electron microscopy (FE-SEM), and (i–k) cross-polarizer-based techniques.

Anisotropically oriented structures engender materials with anisotropic mechanical properties.13 The mechanical properties of the CNF hydrogels prepared using the electrophoretic and electrochemical method depend significantly on their orientation. The compressive moduli of the CNF hydrogels, for example, reflected their orientation states and were observed to be asymmetric with respect to the compression direction (Figure S5). The vertically oriented CNF hydrogel was less deformable under vertical compression and five times more deformable under horizontal compression. In addition, the surface of the horizontally oriented CNF hydrogel was observed to be smooth and have a low coefficient of friction compared to those of randomly oriented CNF hydrogels (Figure S6, Table S1).

The simplicity and flexibility of this method are the most important characteristic. We successfully created CNF hydrogels in the shapes of pillar arrays and flow channels by covering the anode with masks of various shape (Figure 2a, b, c). CNFs were deposited in concentric circles around the pinholes when a mask with pinholes was used, while hydrogel lens arrays were created when the horizontal orientation condition (applied voltage of 1 V) was applied (Figure 2d, e, f).

Figure 2.

Figure 2

Open in a new tab

(a) Pillar arrays and (b) a flow channel were easily achieved. (c) Electrophoretic and electrochemical deposition of CNFs using a mask. (d) Hydrogel lens arrays fabricated using a pinhole mask. (e, f) The three-dimensional CNF oriented shape evaluated using a cross-polarizer.

Multiscale and three-dimensional orientational control, such as in biological systems, has been achieved by the developed method. CNFs were deposited and fixed in any orientation state and at any thickness by tuning the applied voltage, even during the process. A multilayer hydrogel with continuously changing horizontal and vertical orientations was prepared by varying the applied voltage from 1 to 40 V and back to 1 V (Figure 3a–c). The electrode does not have to be flat; three-dimensional electrodes can also be used. A cartilage-like hydrogel capable of seamlessly transitioning from vertical to horizontal was prepared by inserting a spherical electrode in the CNF/water dispersion and varying the applied voltage from 40 to 1 V (Figure 3d–f). A three-dimensional plant-stem-like CNF hydrogel was prepared by combining a thin wire electrode with a plate electrode (Figure 3g–k).

Figure 3.

Figure 3

Open in a new tab

(a) Multilayered CNF hydrogel. (b) Cross-section of the multilayered CNF hydrogel observed through a cross-polarizer. (c) By controlling the applied voltage, CNFs were deposited in the order horizontal, vertical, random, and horizontal with respect to the anode. (d) Cartilage-like CNF hydrogel formed around a spherical electrode. (e) Cross-section observed through a cross-polarizer. (f) Corresponding schematic diagram. (g) Plant-stem-like CNF hydrogel prepared by combining wire and flat electrodes. (h, j) Corresponding cross-section. (i, k) Corresponding schematic diagram.

The applicability of the devised electrophoretic and electrochemical deposition method is not limited to the formation of oriented CNF hydrogels. The oriented CNF hydrogels anisotropically shrank upon drying, which is ascribable to the CNF orientation throughout the hydrogel (Figure S7). The anisotropic shrinking of the oriented CNF hydrogels was exploited for applications by combining it with three-dimensional orientation control and mask patterning. The CNFs formed in a horizontal orientation with respect to the electrode surface when deposited on a three-dimensional electrode at 1 V (Figure 4a, b). The subsequently formed horizontally oriented CNF hydrogel dried without cracking because drying-related shrinkage is suppressed in the horizontal direction, resulting in a smooth dry film on the electrode (Figure 4c). The electrodes were removed after drying to obtain molded CNF films with various three-dimensional shapes (Figure 4d–g). As for the vertical orientation, it was possible to form microneedle-like structures in combination with mask patterning by taking advantage of the fact that vertical shrinkage is suppressed during drying (Figure 4h–j). It is also possible to fix the CNF hydrogel and dried CNF material not only on the electrode surface but also on a porous material, such as filter paper. CNF moldings prepared by this method adsorb copper ions supplied from the anode. Therefore, in addition to the inherent properties of CNF structural materials (e.g., light weight, high strength, and high thermal resistance28−32), functional properties, such as antiviral properties toward COVID-19, were also provided (Table S2). In addition, the copper ions adsorbed on the CNF surface were easily removed by washing with hydrochloric acid33 (Figures S8, S9); therefore, it can be used flexibly according to the application. The introduced electrophoretic and electrochemical deposition method can be used to create a next generation of environmentally friendly alternatives to petroleum-based plastics.

Figure 4.

Figure 4

Open in a new tab

(a) Three-dimensional electrode, (b) horizontally oriented CNF hydrogel fixed on its surface, and (c, d) molded CNF film after drying the CNF hydrogel. Similarly obtained (e) cylindrical, (f) flower-like, and (g) mouthpiece-shaped molded CNF films. (h) Combining mask patterning, porous substrates, and vertically oriented CNFs. (i) CNF hydrogels with sharp structures fixed on porous substrates. (j) CNF microneedles after drying.

CNF orientation can be controlled by several possible mechanisms in this study. Typical factors include the influence of the electric field and ion diffusion from the anode. There are several reports on the CNF orientation under the influence of an electric field.10,11 In most cases, an alternating-current electric field is used, which enables the CNFs to rotate vertically between the two electrodes in situ, which is ascribable to the anisotropic polarization properties of CNFs. However, such orientation requires a strong electric field of several hundred to several thousand V/cm. In this study, we used a direct-current electric field that is significantly weaker than those previously reported (∼12 V/cm). The effect of such a weak electric field on the CNF orientation state needs to be carefully evaluated.

Another possibility involves orientation through ion diffusion from the anode. Various polysaccharides,34−36 fibrous proteins,37,38 DNA,39 and semirigid polyanions40 have been reported to form anisotropic hydrogels through one-way ion diffusion. For example, sodium alginate is well known to orient horizontally with respect to the diffusion plane,34 while semirigid polyanions have been observed to orient horizontally or vertically with respect to the diffusion plane.40 In the electrophoretic and electrochemical method, copper ions, which are CNF cross-linkers (multivalent cations), are supplied from the anode, resulting in gelation. Gelation is caused by ion diffusion from one direction, and the orientation mechanism is likely to be the same as that previously reported. However, the CNF hydrogel becomes randomly41 or chirally nematically oriented through self-alignment42 when a CNF/water dispersion comes into contact with an acidic or aqueous multivalent cation solution from one direction to form a gel. This peculiar orientation phenomenon might be ascribable to the electrophoretic CNF concentration, which produces a concentration gradient suitable for orientation and hydrogel formation at the sol–gel interface.

The applicability of the method was tested on several anionic materials, including sodium alginate and nanoclay, which confirmed that the orientation depends significantly on the voltage conditions (Figures 5, S10). These results not only suggest that the method is applicable to a variety of materials but also realize highly structured nanocomposites and composites of two or more materials.

Figure 5.

Figure 5

Open in a new tab

Horizontally oriented (a) sodium alginate hydrogel and (b) nanoclay hydrogel prepared at an applied voltage of 1 V observed through a cross-polarizer. Randomly and semivertically oriented (c) sodium alginate hydrogel and (d) nanoclay hydrogel prepared at an applied voltage of 40 V observed through a cross-polarizer.

Conclusion

A simple electrophoretic and electrochemical deposition method was developed for controlling and fixing CNF orientation, and its potential applications were investigated. CNFs were fixed in horizontal, random, and vertical orientations with respect to the anode surface by changing the applied voltage. Hierarchical structures, comprising CNFs with different layer-by-layer orientations, were formed in one-pot processes, forming complex geometries. Simplicity and flexibility are the strengths of this method. However, further research on the orientation mechanism is required. CNF size, concentration, dispersion temperature, voltage-application method (DC or pulsed), and the type of electrode metal may also affect the orientation state. Elucidating the mechanism responsible for electrophoretic- and electrochemical-deposition-induced orientational control and additional optimization is expected to assist in the development of nanomaterial composites that mimic biological tissue and the design of highly functional materials.

Experimental Section

Preparation of Cellulose Nanofiber Dispersions and Other Dispersions

TEMPO-oxidized cellulose pulp (carboxyl content, 1.8 mmol/g) was supplied by DKS Co., Ltd. The TEMPO-oxidized cellulose pulp slurry was homogenized using a high-pressure water-jet system (Star Burst, HJP-25008, Sugino Machine Co., Ltd., Japan) equipped with a ball-collision chamber. The injected slurry was repeatedly passed through a small nozzle (⦶ 0.15 mm) under a pressure of 200 MPa. A 0.2 wt % CNF/water dispersion was obtained after the slurry was passed through this nozzle 50 times. The width of the CNFs was ∼3 nm, and the average length of the CNFs was 181 ± 77 nm. The length of the CNFs was determined using an atomic force microscope (AFM, Nanocute, SII Nano Technology Inc., Japan) in the dynamic force microscope (DFM) mode and by using ImageJ software. Laboratory-grade sodium alginate was purchased from Nacalai Tesque, Inc. (Japan) and dissolved in distilled water at a concentration of 0.2 wt %. The nanoclay (laponite)/water dispersion was kindly provided by Dr. Zhifang Sun, RIKEN (Japan). Laponite XLG (LPN, thickness ∼1 nm; lateral size ∼25 nm) was purchased from Rockwood Additives Ltd. (UK). LPN powder (4.5 g) was dispersed in water (50 mL) and vigorously stirred for 10 min at 25 °C to form a homogeneous slurry with a concentration of 9 wt %. The slurry was diluted to 0.4 wt % before use.

Electrophoretic and Electrochemical Deposition

Copper and graphite electrodes were placed at the bottom and top of an acrylic cell, respectively (anode size: 10 × 10 mm; distance between the electrodes: 35 mm). Voltage in the 1–40 V range was applied across the electrodes using a source measure unit (B2902A, Keysight Technologies, USA), and the cell was filled with a 0.2 wt % CNF/water dispersion (150 mL). The CNF/water dispersion was neutral (pH: ∼7), and the temperature was maintained at room temperature (∼25 °C) during the voltage application. An acrylic mask was placed on the electrode in certain contexts. A 0.2 wt % sodium alginate solution and a 0.4 wt % nanoclay dispersion were also used under the same conditions as the CNF/water dispersion. Cartilage-like CNF hydrogels were prepared by the electrophoretic deposition of CNFs on spherical copper electrodes, while the applied voltage was gradually decreased from 40 V to 1 V. Plant-stem-like CNF hydrogels were prepared by the deposition of CNFs at an applied voltage of 1 V using electrodes with fine wires arranged orthogonally over a flat electrode.

Structural Characterization of CNF Hydrogels

A 15-mm-thick mask with a 10 × 10 mm square hole was used to create the CNF hydrogel. Voltages of 1, 10, and 40 V for 72, 10, and 2 h, respectively, were required to grow each hydrogel to a thickness of 15 mm. A 5 × 5 × 15 mm hollow was formed in the center of a 10 × 10 × 15 mm prismatic hydrogel and used to evaluate orientation. CNF aerogels were prepared by replacing ethanol in the CNF hydrogels, followed by supercritical drying (SYGLCP-8, Sanyu Gijutsu, Japan). Transmission X-ray diffractometry (XRD) was used to examine CNF orientation in the aerogels. The XRD patterns of the CNF aerogels were recorded on Fujifilm imaging plates under vacuum using a Rigaku MicroMax-007HF instrument operating at 40 kV and 30 mA with Cu Kα radiation (λ = 0.154 18 nm). The aerogels were set perpendicular to the X-ray beam, and the distances from the imaging plates were calibrated using NaF. The order parameter was calculated using a previously reported method.6,8,9 In this study, the order parameters range from 0 to 1, where 0 represents a random alignment and 1 represents perfect CNF alignment. The sample was placed at an angle of 0° or 45° to the cross-polarizer. The osmium-treated cross-sections of the CNF aerogels were examined by field-emission scanning electron microscopy (SEM; S-4800, Hitachi, Japan) at 1.5 kV.

Preparation of CNF Moldings

Electrodes were prepared using copper-based conductive paint (SP-D-03, Freedom Custom Guitar Research Co. Ltd., Japan) and commercially available paraffin wax. CNFs were deposited on the meltable electrode surface in the horizontal orientation at an applied voltage of 1 V. The horizontally oriented CNF hydrogels formed on the electrode surface were dried at 10 °C and 90% RH. The molded CNF film was obtained through heating at 80 °C and washing with lacquer thinner to remove the electrodes. CNF microneedles were prepared by drying vertically oriented CNF hydrogels patterned with a mask at an applied voltage of 40 V on filter paper, at 10 °C and 90% RH.

Acknowledgments

We thank Dr. Zhifang Sun for providing the nanoclay dispersion. We thank D.D.S. Satoko Nagamine for her advice in making the mouthpiece. This work was partially supported by Grants-in-Aid for Scientific Research (Grant Number 19J202410 to T.K.) and JST ACT-X (Grant Number JPMJAX21K3).

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsnano.2c06392.

  • Typical current density changes during voltage application, FT-IR and XRF spectra of CNF aerogels, WAXS images and azimuthal intensity profiles for CNF aerogels, compressive moduli of CNF hydrogels in different orientations, the demonstration of scalability of CNF hydrogel formation, drying-related shrinkage of CNF hydrogels, removal of copper ions adsorbed on CNFs by hydrochloric acid, cross-section of an alginate hydrogel and a nanoclay hydrogel, results of friction coefficient measurements for CNF hydrogels, and antiviral testing of molded CNF films against SARS-CoV-2 (PDF)

Author Contributions

T.K. was responsible for the project idea, manuscript preparation, and experiments. T.S. and M.N. provided critical feedback on results. H.K. contributed to data interpretation. All authors have provided feedback and endorse the final version of the manuscript.

The authors declare no competing financial interest.

Supplementary Material

nn2c06392_si_001.pdf (748.2KB, pdf)

References

  1. Fratzl P.; Weinkamer R. Nature’s Hierarchical Materials. Prog. Mater. Sci. 2007, 52 (8), 1263–1334. 10.1016/j.pmatsci.2007.06.001. [DOI] [Google Scholar]
  2. Gibson L. J. The Hierarchical Structure and Mechanics of Plant Materials. J. R. Soc. Interface. 2012, 9 (76), 2749–2766. 10.1098/rsif.2012.0341. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Allen R.; Wardrop A. The Opening and Shedding Mechanism of the Female Cones of Pinus Radiata. Aust. J. Bot. 1964, 12 (2), 125. 10.1071/BT9640125. [DOI] [Google Scholar]
  4. Elbaum R.; Gorb S.; Fratzl P. Structures in the Cell Wall That Enable Hygroscopic Movement of Wheat Awns. J. Struct. Biol. 2008, 164 (1), 101–107. 10.1016/j.jsb.2008.06.008. [DOI] [PubMed] [Google Scholar]
  5. Sophia Fox A. J.; Bedi A.; Rodeo S. A. The Basic Science of Articular Cartilage: Structure, Composition, and Function. Sports Health 2009, 1 (6), 461–468. 10.1177/1941738109350438. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Lin X. Y.; Wang Z. J.; Pan P.; Wu Z. L.; Zheng Q. Monodomain Hydrogels Prepared by Shear-Induced Orientation and Subsequent Gelation. RSC Adv. 2016, 6 (97), 95239–95245. 10.1039/C6RA17103F. [DOI] [Google Scholar]
  7. Yoshiharu N.; Shigenori K.; Masahisa W.; Takeshi O. Cellulose Microcrystal Film of High Uniaxial Orientation. Macromolecules 1997, 30 (20), 6395–6397. 10.1021/ma970503y. [DOI] [Google Scholar]
  8. Choi S.; Kim J. Designed Fabrication of Super-Stiff, Anisotropic Hybrid Hydrogels via Linear Remodeling of Polymer Networks and Subsequent Crosslinking. J. Mater. Chem. B 2015, 3 (8), 1479–1483. 10.1039/C4TB01852D. [DOI] [PubMed] [Google Scholar]
  9. Uetani K.; Okada T.; Oyama H. T. In-Plane Anisotropic Thermally Conductive Nanopapers by Drawing Bacterial Cellulose Hydrogels. ACS Macro Lett. 2017, 6 (4), 345–349. 10.1021/acsmacrolett.7b00087. [DOI] [PubMed] [Google Scholar]
  10. Wise H. G.; Takana H.; Ohuchi F.; Dichiara A. B. Field-Assisted Alignment of Cellulose Nanofibrils in a Continuous Flow-Focusing System. ACS Appl. Mater. Interfaces 2020, 12 (25), 28568–28575. 10.1021/acsami.0c07272. [DOI] [PubMed] [Google Scholar]
  11. Brouzet C.; Mittal N.; Rosén T.; Takeda Y.; Söderberg L. D.; Lundell F.; Takana H. Effect of Electric Field on the Hydrodynamic Assembly of Polydisperse and Entangled Fibrillar Suspensions. Langmuir 2021, 37 (27), 8339–8347. 10.1021/acs.langmuir.1c01196. [DOI] [PubMed] [Google Scholar]
  12. Kimura F.; Kimura T.; Tamura M.; Hirai A.; Ikuno M.; Horii F. Magnetic Alignment of the Chiral Nematic Phase of a Cellulose Microfibril Suspension. Langmuir 2005, 21 (5), 2034–2037. 10.1021/la0475728. [DOI] [PubMed] [Google Scholar]
  13. Markstedt K.; Mantas A.; Tournier I.; Martínez Ávila H.; Hägg D.; Gatenholm P. 3D Bioprinting Human Chondrocytes with Nanocellulose–Alginate Bioink for Cartilage Tissue Engineering Applications. Biomacromolecules 2015, 16 (5), 1489–1496. 10.1021/acs.biomac.5b00188. [DOI] [PubMed] [Google Scholar]
  14. 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 (1), 4018. 10.1038/ncomms5018. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Uetani K.; Koga H.; Nogi M. Checkered Films of Multiaxis Oriented Nanocelluloses by Liquid-Phase Three-Dimensional Patterning. Nanomaterials 2020, 10 (5), 958. 10.3390/nano10050958. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Kilian D.; Ahlfeld T.; Akkineni A. R.; Bernhardt A.; Gelinsky M.; Lode A. 3D Bioprinting of Osteochondral Tissue Substitutes – in Vitro-Chondrogenesis in Multi-Layered Mineralized Constructs. Sci. Rep. 2020, 10 (1), 8277. 10.1038/s41598-020-65050-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Saadi M. A. S. R.; Maguire A.; Pottackal N. T.; Thakur M. S. H.; Ikram M. Md.; Hart A. J.; Ajayan P. M.; Rahman M. M. Direct Ink Writing: A 3D Printing Technology for Diverse Materials. Adv. Mater. 2022, 34, 2108855. 10.1002/adma.202108855. [DOI] [PubMed] [Google Scholar]
  18. Chen Y.; Li S.; Li X.; Mei C.; Zheng J.; E S.; Duan G.; Liu K.; Jiang S. Liquid Transport and Real-Time Dye Purification via Lotus Petiole-Inspired Long-Range-Ordered Anisotropic Cellulose Nanofibril Aerogels. ACS Nano 2021, 15 (12), 20666–20677. 10.1021/acsnano.1c10093. [DOI] [PubMed] [Google Scholar]
  19. Lin Z.; Dong J.; Wang X.; Huang Q.; Shen X.; Yang M.; Sun X.; Yuan Y.; Wang S.; Ning Y.; Yang S.; Yin W.; Li M.; Sun Y.; Zhang Q.; Li Y. Twin-Structured Graphene Metamaterials with Anomalous Mechanical Properties. Adv. Mater. 2022, 34 (17), 2200444. 10.1002/adma.202200444. [DOI] [PubMed] [Google Scholar]
  20. Shahbazi M.-A.; Ghalkhani M.; Maleki H. Directional Freeze-Casting: A Bioinspired Method to Assemble Multifunctional Aligned Porous Structures for Advanced Applications. Adv. Eng. Mater. 2020, 22 (7), 2000033. 10.1002/adem.202000033. [DOI] [Google Scholar]
  21. Sano K.; Ishida Y.; Aida T. Synthesis of Anisotropic Hydrogels and Their Applications. Angew. Chem., Int. Ed. 2018, 57 (10), 2532–2543. 10.1002/anie.201708196. [DOI] [PubMed] [Google Scholar]
  22. Kasuga T.; Yagyu H.; Uetani K.; Koga H.; Nogi M. Cellulose Nanofiber Coatings on Cu Electrodes for Cohesive Protection against Water-Induced Short-Circuit Failures. ACS Appl. Nano Mater. 2021, 4 (4), 3861–3868. 10.1021/acsanm.1c00267. [DOI] [Google Scholar]
  23. Kim H.; Endrődi B.; Salazar-Alvarez G.; Cornell A. One-Step Electro-Precipitation of Nanocellulose Hydrogels on Conducting Substrates and Its Possible Applications: Coatings, Composites, and Energy Devices. ACS Sustainable Chem. Eng. 2019, 7 (24), 19415–19425. 10.1021/acssuschemeng.9b04171. [DOI] [Google Scholar]
  24. Guo X.; Gao H.; Zhang J.; Zhang L.; Shi X.; Du Y. One-Step Electrochemically Induced Counterion Exchange to Construct Free-Standing Carboxylated Cellulose Nanofiber/Metal Composite Hydrogels. Carbohydr. Polym. 2021, 254, 117464. 10.1016/j.carbpol.2020.117464. [DOI] [PubMed] [Google Scholar]
  25. Chen Q.; de Larraya U. P.; Garmendia N.; Lasheras-Zubiate M.; Cordero-Arias L.; Virtanen S.; Boccaccini A. R. Electrophoretic Deposition of Cellulose Nanocrystals (CNs) and CNs/Alginate Nanocomposite Coatings and Free Standing Membranes. Colloids Surfaces B Biointerfaces 2014, 118, 41–48. 10.1016/j.colsurfb.2014.03.022. [DOI] [PubMed] [Google Scholar]
  26. Atifi S.; Mirvakili M.-N.; Williams C. A.; Bay M. M.; Vignolini S.; Hamad W. Y.; Atifi S.; Mirvakili M.-N.; Hamad W. Y.; Williams C. A.; Bay M. M.; Vignolini S. Fast Self-Assembly of Scalable Photonic Cellulose Nanocrystals and Hybrid Films via Electrophoresis. Adv. Mater. 2022, 34 (12), 2109170. 10.1002/ADMA.202109170. [DOI] [PubMed] [Google Scholar]
  27. Avcu E.; Baştan F. E.; Abdullah H. Z.; Rehman M. A. U.; Avcu Y. Y.; Boccaccini A. R. Electrophoretic Deposition of Chitosan-Based Composite Coatings for Biomedical Applications: A Review. Prog. Mater. Sci. 2019, 103, 69–108. 10.1016/j.pmatsci.2019.01.001. [DOI] [Google Scholar]
  28. Nogi M.; Iwamoto S.; Nakagaito A. N.; Yano H. Optically Transparent Nanofiber Paper. Adv. Mater. 2009, 21 (16), 1595–1598. 10.1002/adma.200803174. [DOI] [Google Scholar]
  29. Fukuzumi H.; Saito T.; Iwata T.; Kumamoto Y.; Isogai A. Transparent and High Gas Barrier Films of Cellulose Nanofibers Prepared by TEMPO-Mediated Oxidation. Biomacromolecules 2009, 10 (1), 162–165. 10.1021/bm801065u. [DOI] [PubMed] [Google Scholar]
  30. Yagyu H.; Ifuku S.; Nogi M. Acetylation of Optically Transparent Cellulose Nanopaper for High Thermal and Moisture Resistance in a Flexible Device Substrate. Flex. Print. Electron. 2017, 2 (1), 014003. 10.1088/2058-8585/aa60f4. [DOI] [Google Scholar]
  31. Kasuga T.; Isobe N.; Yagyu H.; Koga H.; Nogi M. Clearly Transparent Nanopaper from Highly Concentrated Cellulose Nanofiber Dispersion Using Dilution and Sonication. Nanomaterials 2018, 8 (2), 104. 10.3390/nano8020104. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Kasuga T.; Yagyu H.; Uetani K.; Koga H.; Nogi M. Return to the Soil” Nanopaper Sensor Device for Hyperdense Sensor Networks. ACS Appl. Mater. Interfaces 2019, 11 (46), 43488–43493. 10.1021/acsami.9b13886. [DOI] [PubMed] [Google Scholar]
  33. Isobe N.; Chen X.; Kim U. J.; Kimura S.; Wada M.; Saito T.; Isogai A. TEMPO-Oxidized Cellulose Hydrogel as a High-Capacity and Reusable Heavy Metal Ion Adsorbent. J. Hazard. Mater. 2013, 260, 195–201. 10.1016/j.jhazmat.2013.05.024. [DOI] [PubMed] [Google Scholar]
  34. Narita T.; Tokita M. Liesegang Pattern Formation in κ-Carrageenan Gel. Langmuir 2006, 22 (1), 349–352. 10.1021/la0522350. [DOI] [PubMed] [Google Scholar]
  35. Dobashi T.; Tomita N.; Maki Y.; Chang C. P.; Yamamoto T. An Analysis of Anisotropic Gel Forming Process of Chitosan. Carbohydr. Polym. 2011, 84 (2), 709–712. 10.1016/j.carbpol.2010.07.004. [DOI] [Google Scholar]
  36. Maki Y.; Ito K.; Hosoya N.; Yoneyama C.; Furusawa K.; Yamamoto T.; Dobashi T.; Sugimoto Y.; Wakabayashi K. Anisotropic Structure of Calcium-Induced Alginate Gels by Optical and Small-Angle X-Ray Scattering Measurements. Biomacromolecules 2011, 12 (6), 2145–2152. 10.1021/bm200223p. [DOI] [PubMed] [Google Scholar]
  37. Furusawa K.; Sato S.; Masumoto J.; Hanazaki Y.; Maki Y.; Dobashi T.; Yamamoto T.; Fukui A.; Sasaki N. Studies on the Formation Mechanism and the Structure of the Anisotropic Collagen Gel Prepared by Dialysis-Induced Anisotropic Gelation. Biomacromolecules 2012, 13 (1), 29–39. 10.1021/bm200869p. [DOI] [PubMed] [Google Scholar]
  38. Mredha Md. T. I.; Zhang X.; Nonoyama T.; Nakajima T.; Kurokawa T.; Takagi Y.; Gong J. P. Swim Bladder Collagen Forms Hydrogel with Macroscopic Superstructure by Diffusion Induced Fast Gelation. J. Mater. Chem. B 2015, 3 (39), 7658–7666. 10.1039/C5TB00877H. [DOI] [PubMed] [Google Scholar]
  39. Furusawa K.; Minamisawa Y.; Dobashi T.; Yamamoto T. Dynamics of Liquid Crystalline Gelation of DNA. J. Phys. Chem. B 2007, 111 (51), 14423–14430. 10.1021/jp076135. [DOI] [PubMed] [Google Scholar]
  40. Wu Z. L.; Kurokawa T.; Sawada D.; Hu J.; Furukawa H.; Gong J. P. Anisotropic Hydrogel from Complexation-Driven Reorientation of Semirigid Polyanion at Ca 2+ Diffusion Flux Front. Macromolecules 2011, 44 (9), 3535–3541. 10.1021/ma2001228. [DOI] [Google Scholar]
  41. Dong H.; Snyder J. F.; Williams K. S.; Andzelm J. W. Cation-Induced Hydrogels of Cellulose Nanofibrils with Tunable Moduli. Biomacromolecules 2013, 14 (9), 3338–3345. 10.1021/bm400993f. [DOI] [PubMed] [Google Scholar]
  42. Saito T.; Uematsu T.; Kimura S.; Enomae T.; Isogai A. Self-Aligned Integration of Native Cellulose Nanofibrils towards Producing Diverse Bulk Materials. Soft Matter 2011, 7 (19), 8804. 10.1039/c1sm06050c. [DOI] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

nn2c06392_si_001.pdf (748.2KB, pdf)

Articles from ACS Nano are provided here courtesy of American Chemical Society

RESOURCES