Download Hi-Res ImageDownload to MS-PowerPointCite This:ACS Appl. Nano Mater. 2020, 3, 10, 10246-10251
This publication is Open Access under the license indicated. Learn More
Article
Coaxial Spinning of Oriented Nanocellulose Filaments and Core–Shell Structures for Interactive Materials and Fiber-Reinforced CompositesClick to copy article linkArticle link copied!
- Andrew Marais*Andrew Marais*Email: [email protected], [email protected]Division of Fiber Technology at the Department of Fiber and Polymer Technology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Teknikringen 56-58, Stockholm SE-100 44, SwedenMore by Andrew Marais
- Johan ErlandssonJohan ErlandssonDivision of Fiber Technology at the Department of Fiber and Polymer Technology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Teknikringen 56-58, Stockholm SE-100 44, SwedenMore by Johan Erlandsson
- L. Daniel SöderbergL. Daniel SöderbergWallenberg Wood Science Center, KTH Royal Institute of Technology, Teknikringen 56, SE-100 44 Stockholm, SwedenMore by L. Daniel Söderberg
- Lars Wågberg*Lars Wågberg*Email: [email protected]Division of Fiber Technology at the Department of Fiber and Polymer Technology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Teknikringen 56-58, Stockholm SE-100 44, SwedenWallenberg Wood Science Center, KTH Royal Institute of Technology, Teknikringen 56, SE-100 44 Stockholm, SwedenMore by Lars Wågberg
Abstract
Click to copy section linkSection link copied!
Spinning filaments from nature’s own high-performance building block, cellulose nanofibrils (CNFs), requires additional considerations compared to conventional manmade fibers commonly made from polymer solutions or melts. We herein utilize the colloidal properties of the highly anisotropic CNFs and demonstrate the preparation of core–shell filaments using a coaxial nozzle. The nanofibril dispersion is passed through the core channel, and the sheath flow consists of a functionalizing solution. The flow rates of the suspensions/solutions are carefully controlled to create an extensional flow at the exit of the nozzle, allowing orientation of the nanofibers into continuous filaments that are then extruded into a fixation bath before drying. The self-assembly mechanism relies on the control of the colloidal stability of carboxymethylated CNFs altered by pH or ionic strength changes. In the simplest approach, HCl is used in the sheath flow to assemble the accelerated CNFs in the core flow, leading to an irreversible association of the nanofibers into an oriented filament. The filaments are continuous and homogeneous, with a dry diameter of approximately 20 μm. The orientation of the CNFs in the spun filament was investigated by wide-angle X-ray scattering, and an orientation index of 0.79 is achieved. The tensile strength of the filaments is 431 ± 89 MPa, the Young’s modulus is 19.2 ± 3.4 GPa, and the strain at break is 7.4 ± 1.3%. Core–shell structures are also prepared by incorporating active materials such as carbon nanotubes in the sheath flow. The resulting filaments show a thin shell of a conductive nanotube network covering a core of cellulose nanofibrils, and the conductivity of such structures reaches 1000 S cm–1, opening up opportunities for composites and interactive materials.
Copyright © 2020 American Chemical Society
Introduction
Click to copy section linkSection link copied!
The interest and knowledge in the synthesis and use of nanometer-sized particles and fibers have expanded over the last decade. Together with the societal growing demand for a broader use of bio-based and renewable resources, this has triggered the emergence of a new class of materials, including wood-based nanomaterials, suggested as a potential candidate to fulfill the criteria of both being renewable and constituting high-performance building blocks in interactive materials, and fiber-reinforced composites. (1,2) Cellulose nanofibers (CNFs) are obtained by defibrillating cellulose-rich wood-based fibers by chemical and mechanical treatments. Most commonly, the chemical treatment of these fibers are performed through carboxymethylation (3) or 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, (4) which significantly facilitates fibrillation through mechanical treatments such as grinding or homogenization where shear forces act to delaminate and isolate individual nanofibrils. The chemical treatments result in a negative surface charge of the liberated nanofibrils, which typically are 4 nm in width and up to a few μm in length. (5)
Because of their high aspect ratio and surface charge, CNFs form gels or volume-spanning arrested states, i.e., colloidal glasses, already at low concentrations, and the decrease in pH and/or increase in ionic strength will drastically influence their colloidal behavior. (6,7) CNFs can be used to self-assemble into different types of materials with remarkable properties such as dense films, membranes, or porous foams and aerogels. These materials can then further be functionalized by surface treatment, adsorption of polymers and nanoparticles, and in situ polymerization, which makes CNFs a building block of major interest in the design of renewable functional materials. (8−11)
From an engineering point of view, it is challenging to assemble nanofibers into an organized hierarchical structure as nature does. However, with extensive knowledge of fibril characteristics, such as morphology, size, aspect ratio, electrostatic charge, dispersive properties, and colloid stability, it is possible to assemble strong and oriented microscopic or macroscopic structures stabilized by secondary interactions between the nanofibrils. One route to achieve this is to wet spin CNF filaments by extruding a nanofiber dispersion into a fixation bath, which results in continuous filaments with a high degree of alignment. (12−14) Apart from the CNF aspect ratio and charge, the solid content, shear rate, and drying conditions have been shown to significantly affect the properties of the spun filaments. (11) Provided that the mechanical treatment processes for preparing CNF are energy-efficient, (15) the use of water-based CNF systems in filament spinning could be a way to prepare cellulose I filaments and to circumvent the dissolution, regeneration, and spinning of cellulose, often requiring more aggressive solvents and processes. (16) It is also possible to dry spin CNF filaments by extruding highly viscous CNF gels into air. However, the resulting filaments tend to have irregular and noncircular cross sections and diameters up to 200 μm. (17)
Using the concept of microfluidics, a flow-focusing technique was recently developed and applied, where the main flow (core flow) consisting of a dilute CNF dispersion is exposed to two perpendicular flows (sheath flows). These sheath flows induce an extensional flow field in the core flow, which aligns the nanofibers. The sheath flows consist of a salt solution or dilute acid, which induces self-association of the nanofibers, and the resulting gel thread is extruded in a bath containing deionized water or salt solutions. (18) This technique was later improved by implementing an additional sheath flow step: in the first step, the CNF dispersion is aligned using deionized water in the sheath flows, and in the second step, the sheath flows induce both alignment and self-association using HCl before being extruded in a HCl bath. (19) This flow-focusing technology was also used to prepare the strongest bio-based filament ever made, so far, as well as bioactive composites. (20) This experimental procedure is very versatile and provides a new toolbox for the preparation of many types of specially designed filaments, since the properties can be further improved and tailored by using additives, cross-linkers or additional postprocessing steps. (19,21,22) Being the state-of-the-art when it comes to a CNF filament in terms of alignment and mechanical properties, this universal method is presently sensitive to processing parameters, and the possibility to scale up the technology has still to be proven.
In this contribution we introduce a facile and scalable route for the extrusion of CNF filaments as well as core–shell filaments. The setup consists in a simple coaxial needle mounted with an extension tube, with the aim of reproducing the three key steps for CNF filament preparation (as provided by the flow-focusing technology): flow acceleration, fibril alignment, and final self-association into a filament. (18) The results show that it is possible to prepare continuous filaments of CNF, i.e., cellulose I, with diameters of ca. 20 μm and an orientation index of 0.79. In addition, it is possible to incorporate active nanoparticles and prepare core–shell structures, here demonstrated by fabricating a filament with a CNF core and a shell composed of conductive carbon nanotubes (CNT), reaching conductivities of 1000 S cm–1. Such materials could potentially be used in applications such as nonwovens, textiles, electronic devices, and biomedicine, and the method opens up various possibilities of interactive and composite filaments with a scale-up potential. By using montmorillonite clay in the sheath flow, it is also demonstrated that it is possible to prepare a mineral filament surface while the mechanical properties of the filament are dominated by the CNF core showing similar mechanical properties as a pure CNF filament. Potentially, this filament type could be used in fire protection applications.
Experimental Section
Click to copy section linkSection link copied!
CNF Preparation
Carboxymethylated CNF with a charge of 600 μeq g–1, length up to 1 μm, and diameter of 5–15 nm was provided by RISE Bioeconomy AB (Stockholm, Sweden) and prepared following the previously described procedure. (3) Prior to use, the CNF aqueous gel was diluted to 4 g L–1 in Milli-Q water, mixed using an Ultra-Turrax at 12000 rpm for 15 min, and ultrasonicated at 50% intensity for 20 min using Sonics VC 750 equipment.
Filament Spinning
Filaments were prepared using a setup consisting of a coaxial needle, fed with two syringe pumps, and mounted with a silicone tubular extension, which was submerged into a collection bath into which the dispersion is extruded. The coaxial needle is made of an internal needle (inner diameter, 510 μm; outer diameter, 1230 μm) an external needle (inner diameter, 1370 μm; outer diameter, 2230 μm). The extension is 10 mm long and has a diameter of 735 μm. The flow speeds were set to 8.4 (core flow) and 50 mL h–1 (sheath flow), resulting in a Reynolds number (Re) = 32. The extruded wet filaments were collected using a pair of tweezers and dried at room temperature after being fastened at both ends to a frame. For plain CNF filaments, a CNF suspension of 4 g L–1 was used in the core flow, and HCl (pH 2) was used in the sheath flow as well as in the collection bath. For CNT core–shell structures, sulfonated CNTs (sCNTs) were synthesized adapting a procedure described previously: (23) carboxymethylated single wall nanotubes (P3 grade, from Carbon Solutions, Inc., USA) were reacted with 97% sulfuric acid at 250 °C for 18 h. After the reaction, the excess sulfuric acid was washed away by three centrifuge cycles at 4000 rpm for 10 min, and the sCNT suspension was ultrasonicated for 20 min at 75% amplitude using a Sonics VC 750 equipment. Functional filaments were prepared using aqueous 0.1 g L–1 suspension of sCNT or MMT in the sheath flow and adjusted to pH 2 with HCl.
Imaging
An S-4800 field emission scanning electron microscope (FESEM) (Hitachi, Tokyo, Japan) was used to image the filaments.
Tensile Test
The filament mechanical properties were tested by performing uniaxial tensile tests at 50% RH and 23 °C using an Instron 5566 universal testing machine (Norwood, MA, USA) equipped with a 50 N load cell. The span length was 10 mm, and the samples were tested at a rate of 5% min–1. For the evaluation of mechanical properties, the filaments were assumed to be cylindrical, and their diameters were evaluated by SEM imaging. A total of at least 10 specimens were tested for each configuration: Re = 32 and Re = 64.
Wide-Angle X-Ray Scattering
Wide-angle X-ray scattering (WAXS) measurements were performed using an Anton Paar SAXSpoint 2.0 system (Anton Paar, Graz, Austria) equipped with a Microsource X-ray source (Cu Kα radiation, wavelength 0.15418 nm) and a Dectris 2D CMOS Eiger R 1M detector with 75 ×75 μm pixel size. A beam size of approximately 500 μm diameter was used at a sample stage temperature between 25 and 29 °C with a beam path pressure of about 1–2 mbar. The sample-to-detector distance (SDD) was 111 mm. The filaments were mounted on a solid sampler (Anton Paar, Graz, Austria) mounted on a VarioStage (Anton Paar, Graz, Austria). Three to five filament fragments were mounted together in order to maximize the signal-to-noise ratio. The measurements were performed under vacuum. For each sample, five frames each of 17 min duration were read from the detector, giving a total measurement time of 1.4 h per sample. For all samples, the relative transmission was determined and used for scaling of the scattering intensities. The software used for instrument control was SAXSdrive version 2.01.224 (Anton Paar, Graz, Austria), and postacquisition data processing was performed using the software SAXSanalysis version 3.00.042 (Anton Paar, Graz, Austria).
The orientation was determined from the data corresponding to the (2 0 0) crystal plane of cellulose at 15.3 nm–1. The orientation index and order parameters were calculated from the azimuthal integration of the intensity, following the procedure described more in details in previous studies. (18,19) Also, using the following equation, where W1/2 is the full width at half of the maximum of the azimuthal intensity profile:
Electrochemical Evaluation
The electrochemical evaluation of the sCNT-modified filaments was performed with a Biologic VSP potentiostat (Biologic Science Instruments, Seyssinet-Pariset, France) using an approximately 2 cm long filament having 1 M KCl as the electrolyte, an Ag/AgCl electrode as the reference, and a platinum plate as the counter electrode. In order to facilitate handling and contacting, the sCNT-functionalized filament was supported on a glass slide and contacted by adding a small amount of conducting glue. The cyclic voltammetry was performed for potentials between 0.1 and 0.5 V at 10 mV s–1 and the galvanostatic charge/discharge measurements with a constant current of 1 μA.
Results and Discussion
Click to copy section linkSection link copied!
Preparation of Filaments Using the Coaxial Flow
The alignment and assembly of CNFs into filaments is achieved by a coaxial setup as depicted in Figure 1a,b. The core flow consists of a CNF dispersion, and the sheath flow (similar to flow-focusing) consists of a HCl solution at pH 2. Both components are flowing through the coaxial nozzle until they come in contact, followed by acceleration due to a contraction of the diameter of the flow channel. This induced flow acceleration causes the high-aspect-ratio fibrils to orient in the flow direction and in addition, the nanofibrils are self-associated by protonation of the carboxyl groups on the nanofibrils induced by the low pH of the sheath flow. The protonation decreases the electrostatic repulsion between the oriented charged fibrils, which brings them so close together that van der Waals forces will dominate their interaction, locking the oriented filament structure into a continuous gel thread. As can be seen in Figure 1c, the gel thread that is extruded into the bath is homogeneous and regular, showing potential for continuous and larger scale filament preparation. The filament is picked up manually from the extrusion bath (Figure 1d) and dried at room temperature by fixing the ends of a piece of the gel thread to a frame. During the drying process, the diameter decreases by a factor of 10 (Figure 1e), and the equilibrium dry content is reached after a few minutes. Mesoscale structures can be observed on the surface of the dry filaments, similarly to what can be observed when wood fibers are dried and show surface wrinkling, which is probably due to the formation of a moisture gradient during the final stages of drying, leading to surface wrinkling. (24)
Figure 1
Figure 1. (a) Schematic depicting the process of coaxial filament spinning using CNF in the core flow and HCl (pH 2) in the sheath flow (not to scale), (b) 3D schematic of the coaxial extrusion setup showing the flow contraction, (c) photograph of the extrusion of filaments in the extrusion bath (for enhanced contrast, a CNF/CNT black suspension was used (scale bar: 1 cm), (d) photograph of a wet filament (scale bar: 1 cm), (e) optical microscope images of a CNF filament during drying at ambient temperature and RH taken at 2 min interval, showing the diameter reduction and formation of surface mesoscale structures (scale bar: 100 μm).
Morphology and Properties of Coaxially Spun Filaments
The morphology and structure of the filaments is investigated by scanning electron microscopy (SEM), and the collected images are shown in Figure 2a–c. The filaments show a circular cross section and a regular shape along their axis. Some mesoscale structures can be observed at the surface of the filaments, similar to what was previously observed. (18,19) The cross-sectional images reveal a dense and homogeneous cellulose network throughout the filament. In order to characterize and quantify the alignment of the CNF in the filaments, wide-angle X-ray scattering (WAXS) is used, and the results are displayed in Figure 2d–f. From the resulting diffractogram and integrated intensity, an orientation index of 0.79 and an order parameter of 0.63 were obtained. Considering the specimen preparation, WAXS measurements are performed on a bundle of several filaments in order to optimize the signal-to-noise ratio, and the values obtained are actually an underestimation of the orientation and show that the filaments prepared by coaxial spinning are in line with the filaments obtained by the flow-focusing technology, although slightly below the highest reported orientation index (0.86) for carboxymethylated nanocellulose fibrils with similar charge density. (20) This difference is suggested to be due to a difference in the filament diameter, given that the diffusion of protons and thus the gelation is faster in the case of a filament with a smaller diameter, and this limits the possibilities of fibril reorientation after the acceleration step. The larger filaments obtained using the coaxial setup hence allows more time for reorganization.
Figure 2
Figure 2. SEM images of CNF filaments showing (a,b) their surface and (c) cross section. Scale bars are 10, 2,and 5 μm, respectively. (d) WAXS diffractogram (scale bar 5 nm–1) and the related (e) radial and (f) azimuthal integration.
Tensile testing of the fabricated filaments is performed to evaluate the mechanical properties. Due to the size and fragility of the filaments, each specimen is mounted on a paper frame in order to avoid any stress prior to testing. In parallel, a fragment of each specimen is saved for diameter analysis using SEM imaging. A representative stress/strain curve is shown in Figure 3. The tensile strength is 431 ± 89 MPa, the modulus is 19.2 ± 3.4 GPa, and the strain at break is 7.4 ± 1.3%. These values are very similar to the first values reported for flow-focused filaments (18) but lower than the latest and highest reported values for a similar CNF starting material, (20) highlighting the crucial effect of a slight difference in degree of orientation in the mechanical properties of the final filament. Another configuration is also tested, where all flow speeds are doubled up, as well as the extension tube length, giving rise to a Reynolds number twice as high as the reference configuration, i.e., Re = 64. In this case, some discontinuities in the spinning process are observed, whereas no gain in the mechanical properties is obtained: the tensile strength is 288 ± 24 MPa, the Young′s modulus is 14.3 ± 2.8 GPa, and the strain at break is 8.1 ± 1.8%.
Figure 3
Figure 3. Tensile stress/strain testing of CNF filaments. Inset depicts the sample preparation/fixation where the filaments are glued on a paper frame in order to minimize the pretesting stress.
Preparation and Functionality of Filaments Prepared Using Sheath Flows of Functional Components
Due to the coaxial design of the setup, it is possible to prepare filaments with a core–shell structure. Adding active materials in the shell at pH 2 gives rise to a filament with a dense CNF core and a thin shell of the active material added. As an example, conductive CNT–CNF filaments have been fabricated (Figure 4a). As pristine CNTs or carboxymethylated CNTs could not form a stable colloidal dispersion at the required low pH, instead, sulfonated CNTs (sCNTs) were used. Using the same settings as for the plain CNF system but passing a pH 2 sCNT suspension in the sheath flow results in the formation of a core (CNF)–shell (sCNT) filament with similar morphology and dimensions as the CNF filaments. SEM imaging (Figure 4b,c) of the cross section of such core–shell structures shows a dense CNF core coated with a thin sCNT layer. For the nonsputtered specimens, SEM images reveal a sharp sCNT-covered surface, whereas charging can be observed in the core, showing that the core is composed of a nonconductive CNF and that sCNTs can only be found onto the surface of the filament (Figure S1).
Figure 4
Figure 4. Coaxial core (CNF)/shell (sCNT) filaments: (a) Schematic depicting the principle and chemical composition of the core and sheath flows, (b) SEM picture of the cross section (scale bar: 5 μm) and (c) inset showing the interface between the CNF core and sCNT shell (scale bar: 500 nm), (d) cyclic voltammogram recorded at a scan rate of 10 mV s–1 in 1 M KCl, and (e) galvanostatic cycling.
By using SEM images, the thickness of the CNT film can be estimated to 100 nm. Assuming this thickness all along the filament, a conductivity of 1000 S cm–1 is obtained. CNF–sCNT core shell filaments are also evaluated electrochemically, and a typical cyclic voltammogram as well as galvanostatic cycling experiment are shown in Figure 4d,e. The CV plot shows a supercapacitor-like square-shaped response, characteristic of carbon materials, and the cycling shows a stable response, showing that the surface of the filament is coated with a thin homogeneous and percolating film of CNT, giving rise to a typical supercapacitor behavior.
The versatility of the coaxial nozzle to produce different core–shell structures was also demonstrated by switching the sheath flow from sCNTs to a stable dispersion of montmorillonite clay (MMT) at pH 2. The continuous process for filament preparation using the coaxial nozzle was unaffected by the switch to an MMT dispersion, and the prepared filaments were of the same dimensions as when the sheath flow was only HCl or sCNTs (Figure 5a). The MMT-containing filaments displayed diameters similar to the HCl-prepared filaments of approximately 20 μm in the dry state. This suggested that there was no extensive incorporation of MMT into the CNF core, and this was corroborated by SEM images of the filament surface, which indeed showed that MMT sheets were tightly packed on the surface of the filament, see Figure 5a,b, and the surface structure was smoother compared to the CNF-only filaments. The presence of MMT on only the surface was further corroborated by observations of the cross sections of the MMT-coated filament, which showed that the MMT was deposited only on the surface of the filament. The two morphologies, CNFs and MMT, are clearly distinguishable in Figure 5b. This is similar to that observed for the sCNTs, which were also only deposited on the surface of the filament. The MMT coating consisted of only a few MMT sheets stacked on top of each other covering the whole filament surface, see Figure 5b. The MMT-coated filaments were mechanically evaluated and revealed that no detrimental effect on the mechanical properties by using MMT in the sheath flow was induced, and the properties were in the same range as HCl-formed filaments. This coverage of the filaments with a distinct layer of MMT might be interesting for the preparation of fire-retardant filaments, but this was beyond the scope of the present work.
Figure 5
Figure 5. (a) SEM picture of a coaxial core (CNF)/shell (MMT) filament (scale bars, 10 μm; inset, 3 μm) and (b) its cross section showing the distinct layers of MMT on the CNF core (scale bars, 5 μm; inset, 1 μm).
CNT and MMT coaxial fibers shown in the present investigation are among the wide range of potential interactive material and composites that can be achieved by using the coaxial nozzle spinning and careful control of the colloidal stability of nanoparticle aqueous suspensions. As compared to electrospinning, a common technique used to prepare coaxial fibers, (25) the presented method offers great advantages such as the possibility to work with environmentally friendly water-based systems as well as to isolate, spin, and process single continuous filaments, opening up potential upscaling application where continuous filaments can be extruded, dried, and rolled in a continuous process.
Conclusions
Click to copy section linkSection link copied!
This work demonstrates the feasibility of using a coaxial flow setup having only a core flow of CNF dispersion and a sheath flow of dilute HCl in order to continuously spin filaments of aligned CNFs with potential application in interactive and composite materials. Although the separate flows are brought into direct contact with each other in the extension tube and the CNFs start to interact due to the decreased pH, there is enough time for the CNFs to align due to the acceleration of the flows in the extension tube, also without any prior alignment of the CNFs in the core flow. The produced CNF filaments displayed an orientation index of 0.79 and an order parameter 0.63. The tensile strength of the filaments reached 431 ± 89 MPa, a Young’s modulus of 19.2 ± 3.4 GPa, and a strain at break of 7.4 ± 1.3%. The coaxial setup also enabled the use of sheath flows of colloidal dispersions stable at pH 2. Functional filaments were spun having sulfonated CNTs and montmorillonite clay platelets deposited as thin layers on the entire surface of the spun filaments by using CNT and montmorillonite dispersion as sheath flows. The conductivity of the CNT-coated filament reached values of 1000 S cm–1and was demonstrated to work as a supercapacitor electrode with a distinct square-shaped cyclic voltammogram. The possibility of preparing MMT-coated CNF filaments opens up for using the coaxial setup to prepare filaments for other applications, for example, as flame-retardant materials where the CNF–MMT combination has earlier shown promising results.
Supporting Information
Click to copy section linkSection link copied!
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsanm.0c02192.
SEM image of a nonsputtered core–shell CNF–CNT filament (PDF)
Terms & Conditions
Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.
Author Information
Click to copy section linkSection link copied!
- Lars Wågberg - Division of Fiber Technology at the Department of Fiber and Polymer Technology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Teknikringen 56-58, Stockholm SE-100 44, Sweden; Wallenberg Wood Science Center, KTH Royal Institute of Technology, Teknikringen 56, SE-100 44 Stockholm, Sweden;
http://orcid.org/0000-0001-8622-0386;
- Johan Erlandsson - Division of Fiber Technology at the Department of Fiber and Polymer Technology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Teknikringen 56-58, Stockholm SE-100 44, Sweden;http://orcid.org/0000-0003-1874-2187
- L. Daniel Söderberg - Wallenberg Wood Science Center, KTH Royal Institute of Technology, Teknikringen 56, SE-100 44 Stockholm, Sweden;http://orcid.org/0000-0003-3737-0091
The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.
Acknowledgments
Click to copy section linkSection link copied!
A.M. acknowledges the Knut & Alice Wallenberg Foundation and Research for funding. J.E. acknowledges the Swedish Energy Agency through the Modulit project (grant no. 37716-1), and Vinnova through the Digitial Cellulose Centre for financial support. L.W. and L.D.S. acknowledge the Wallenberg Wood Science Center for funding through the KAW 2018.0452-WWSC 2.0, Grant. Dr. Anita Teleman and Dr. Frédéric Pouyet are acknowledged for their assistance in WAXS measurements.
References
Click to copy section linkSection link copied!
This article references 25 other publications.
- 1Ling, S.; Kaplan, D. L.; Buehler, M. J. Nanofibrils in Nature and Materials Engineering. Nat. Rev. Mater. 2018, 3, 18016, DOI: 10.1038/natrevmats.2018.16Google Scholar1Nanofibrils in nature and materials engineeringLing, Shengjie; Kaplan, David L.; Buehler, Markus J.Nature Reviews Materials (2018), 3 (4), 18016CODEN: NRMADL; ISSN:2058-8437. (Nature Research)Nanofibrillar materials, such as cellulose, chitin and silk, are highly ordered architectures, formed through the self-assembly of repetitive building blocks into higher-order structures, which are stabilized by non-covalent interactions. This hierarchical building principle endows many biol. materials with remarkable mech. strength, anisotropy, flexibility and optical properties, such as structural color. These features make nanofibrillar biopolymers interesting candidates for the development of strong, sustainable and biocompatible materials for environmental, energy, optical and biomedical applications. However, recreating their architecture is challenging from an engineering perspective. Rational design approaches, applying a combination of theor. and exptl. protocols, have enabled the design of biopolymer-based materials through mimicking natures multiscale assembly approach. In this Review, we summarize hierarchical design strategies of cellulose, silk and chitin, focusing on nanoconfinement, fibrillar orientation and alignment in 2D and 3D structures. These multiscale architectures are discussed in the context of mech. and optical properties, and different fabrication strategies for the manufg. of biopolymer nanofibril-based materials are investigated. We highlight the contribution of rational material design strategies to the development of mech. anisotropic and responsive materials and examine the future of the material-by-design paradigm.
- 2Dufresne, A. Nanocellulose: A New Ageless Bionanomaterial. Mater. Today 2013, 16, 220– 227, DOI: 10.1016/j.mattod.2013.06.004Google Scholar2Nanocellulose: a new ageless bionanomaterialDufresne, AlainMaterials Today (Oxford, United Kingdom) (2013), 16 (6), 220-227CODEN: MTOUAN; ISSN:1369-7021. (Elsevier Ltd.)A review. Owing to the hierarchical structure of cellulose, nanoparticles can be extd. from this naturally occurring polymer. Multiple mech. shearing actions allow the release of more or fewer individual microfibrils. Longitudinal cutting of these microfibrils can be achieved by a strong acid hydrolysis treatment, allowing dissoln. of amorphous domains. The impressive mech. properties, reinforcing capabilities, abundance, low d., and biodegradability of these nanoparticles make them ideal candidates for the processing of polymer nanocomposites. With a Young's modulus in the range 100-130 GPa and a surface area of several hundred m2 g-1, new promising properties can be considered for cellulose.
- 3Wågberg, L.; Decher, G.; Norgren, M.; Lindström, T.; Ankerfors, M.; Axnäs, K. The Build-up of Polyelectrolyte Multilayers of Microfibrillated Cellulose and Cationic Polyelectrolytes. Langmuir 2008, 24, 784– 795, DOI: 10.1021/la702481vGoogle Scholar3The build-up of polyelectrolyte multilayers of microfibrillated cellulose and cationic polyelectrolytesWagberg Lars; Decher Gero; Norgren Magnus; Lindstrom Tom; Ankerfors Mikael; Axnas KarlLangmuir : the ACS journal of surfaces and colloids (2008), 24 (3), 784-95 ISSN:0743-7463.A new type of nanocellulosic material has been prepared by high-pressure homogenization of carboxymethylated cellulose fibers followed by ultrasonication and centrifugation. This material had a cylindrical cross-section as shown by transmission electron microscopy with a diameter of 5-15 nm and a length of up to 1 microm. Calculations, using the Poisson-Boltzmann equation, showed that the surface potential was between 200 and 250 mV, depending on the pH, the salt concentration, and the size of the fibrils. They also showed that the carboxyl groups on the surface of the nanofibrils are not fully dissociated until the pH has reached pH = approximately 10 in deionized water. Calculations of the interaction between the fibrils using the Derjaguin-Landau-Verwey-Overbeek theory and assuming a cylindrical geometry indicated that there is a large electrostatic repulsion between these fibrils, provided the carboxyl groups are dissociated. If the pH is too low and/or the salt concentration is too high, there will be a large attraction between the fibrils, leading to a rapid aggregation of the fibrils. It is also possible to form polyelectrolyte multilayers (PEMs) by combining different types of polyelectrolytes and microfibrillated cellulose (MFC). In this study, silicon oxide surfaces were first treated with cationic polyelectrolytes before the surfaces were exposed to MFC. The build-up of the layers was monitored with ellipsometry, and they show that it is possible to form very well-defined layers by combinations of MFC and different types of polyelectrolytes and different ionic strengths of the solutions during the adsorption of the polyelectrolyte. A polyelectrolyte with a three-dimensional structure leads to the build-up of thick layers of MFC, whereas the use of a highly charged linear polyelectrolyte leads to the formation of thinner layers of MFC. An increase in the salt concentration during the adsorption of the polyelectrolyte results in the formation of thicker layers of MFC, indicating that the structure of the adsorbed polyelectrolyte has a large influence on the formation of the MFC layer. The films of polyelectrolytes and MFC were so smooth and well-defined that they showed clearly different interference colors, depending on the film thickness. A comparison between the thickness of the films, as measured with ellipsometry, and the thickness estimated from their colors showed good agreement, assuming that the films consisted mainly of solid cellulose with a refractive index of 1.53. Carboxymethylated MFC is thus a new type of nanomaterial that can be combined with oppositely charged polyelectrolytes to form well-defined layers that may be used to form, for example, new types of sensor materials.
- 4Saito, T.; Kimura, S.; Nishiyama, Y.; Isogai, A. Cellulose Nanofibers Prepared by TEMPO-Mediated Oxidation of Native Cellulose. Biomacromolecules 2007, 8, 2485– 2491, DOI: 10.1021/bm0703970Google Scholar4Cellulose Nanofibers Prepared by TEMPO-Mediated Oxidation of Native CelluloseSaito, Tsuguyuki; Kimura, Satoshi; Nishiyama, Yoshiharu; Isogai, AkiraBiomacromolecules (2007), 8 (8), 2485-2491CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)Never-dried and once-dried hardwood celluloses were oxidized by a 2,2,6,6-tetra-Me piperidine-1-oxyl radical (TEMPO)-mediated system, and highly cryst. and individualized cellulose nanofibers, dispersed in water, were prepd. by mech. treatment of the oxidized cellulose/water slurries. When carboxylate contents formed from the primary hydroxyl groups of the celluloses reached approx. 1.5 mmol/g, the oxidized cellulose/water slurries were mostly converted to transparent and highly viscous dispersions by mech. treatment. Transmission electron microscopic observation showed that the dispersions consisted of individualized cellulose nanofibers 3-4 nm in width and a few microns in length. No intrinsic differences between never-dried and once-dried celluloses were found for prepg. the dispersion, as long as carboxylate contents in the TEMPO-oxidized celluloses reached approx. 1.5 mmol/g. Changes in viscosity of the dispersions during the mech. treatment corresponded with those in the dispersed states of the cellulose nanofibers in water.
- 5Eichhorn, S. J.; Dufresne, A.; Aranguren, M.; Marcovich, N. E.; Capadona, J. R.; Rowan, S. J.; Weder, C.; Thielemans, W.; Roman, M.; Renneckar, S.; Gindl, W.; Veigel, S.; Keckes, J.; Yano, H.; Abe, K.; Nogi, M.; Nakagaito, A. N.; Mangalam, A.; Simonsen, J.; Benight, A. S.; Bismarck, A.; Berglund, L. A.; Peijs, T. Review: Current International Research into Cellulose Nanofibres and Nanocomposites. J. Mater. Sci. 2009, 45, 1– 33, DOI: 10.1007/s10853-009-3874-0Google ScholarThere is no corresponding record for this reference.
- 6Nordenström, M.; Fall, A.; Nyström, G.; Wågberg, L. Formation of Colloidal Nanocellulose Glasses and Gels. Langmuir 2017, 33, 9772– 9780, DOI: 10.1021/acs.langmuir.7b01832Google Scholar6Formation of Colloidal Nanocellulose Glasses and GelsNordenstrom Malin; Fall Andreas; Wagberg Lars; Nystrom GustavLangmuir : the ACS journal of surfaces and colloids (2017), 33 (38), 9772-9780 ISSN:.Nanocellulose (NC) suspensions can form rigid volume-spanning arrested states (VASs) at very low volume fractions. The transition from a free-flowing dispersion to a VAS can be the result of either an increase in particle concentration or a reduction in interparticle repulsion. In this work, the concentration-induced transition has been studied with a special focus on the influence of the particle aspect ratio and surface charge density, and an attempt is made to classify these VASs. The results show that for these types of systems two general states can be identified: glasses and gels. These NC suspensions had threshold concentrations inversely proportional to the particle aspect ratio. This dependence indicates that the main reason for the transition is a mobility constraint that, together with the reversibility of the transition, classifies the VASs as colloidal glasses. If the interparticle repulsion is reduced, then the glasses can transform into gels. Thus, depending on the preparation route, either soft and reversible glasses or stiff and irreversible gels can be formed.
- 7Fall, A. B.; Lindström, S. B.; Sundman, O.; Ödberg, L.; Wågberg, L. Colloidal Stability of Aqueous Nanofibrillated Cellulose Dispersions. Langmuir 2011, 27, 11332– 11338, DOI: 10.1021/la201947xGoogle Scholar7Colloidal Stability of Aqueous Nanofibrillated Cellulose DispersionsFall, Andreas B.; Lindstroem, Stefan B.; Sundman, Ola; Oedberg, Lars; Waagberg, LarsLangmuir (2011), 27 (18), 11332-11338CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)Cellulose nanofibrils constitute an attractive raw material for carbon-neutral, biodegradable, nanostructured materials. Aq. suspensions of these nanofibrils are stabilized by electrostatic repulsion arising from deprotonated carboxyl groups at the fibril surface. In the present work, a new model is developed for predicting colloidal stability by considering deprotonation and electrostatic screening. This model predicts the fibril-fibril interaction potential at a given pH in a given ionic strength environment. Expts. support the model predictions that aggregation is induced by decreasing the pH, thus reducing the surface charge, or by increasing the salt concn. It is shown that the primary mechanism for aggregation upon the addn. of salt is the surface charge redn. through specific interactions of counterions with the deprotonated carboxyl groups, and the screening effect of the salt is of secondary importance.
- 8Lavoine, N.; Desloges, I.; Dufresne, A.; Bras, J. Microfibrillated Cellulose - Its Barrier Properties and Applications in Cellulosic Materials: A Review. Carbohydr. Polym. 2012, 90, 735– 764, DOI: 10.1016/j.carbpol.2012.05.026Google Scholar8Microfibrillated cellulose - Its barrier properties and applications in cellulosic materials: A reviewLavoine, Nathalie; Desloges, Isabelle; Dufresne, Alain; Bras, JulienCarbohydrate Polymers (2012), 90 (2), 735-764CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)A review. Interest in microfibrillated cellulose (MFC) has been increasing exponentially. Its nano-scale dimensions and its ability to form a strong nanoporous network have encouraged the emergence of new high-value applications. The nanoscale characterization possibilities of different MFC materials are thus increasing intensively. Therefore, it is crit. to review such MFC materials and their properties. Moreover, very recent studies have proved the significant barrier properties of MFC (e.g., decrease of water vapor permeability).
- 9Klemm, D.; Kramer, F.; Moritz, S.; Lindström, T.; Ankerfors, M.; Gray, D.; Dorris, A. Nanocelluloses: A New Family of Nature-Based Materials. Angew. Chem. 2011, 50, 5438– 5466, DOI: 10.1002/anie.201001273Google Scholar9Nanocelluloses: A New Family of Nature-Based MaterialsKlemm, Dieter; Kramer, Friederike; Moritz, Sebastian; Lindstroem, Tom; Ankerfors, Mikael; Gray, Derek; Dorris, AnnieAngewandte Chemie, International Edition (2011), 50 (24), 5438-5466CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)A review. Cellulose fibrils with widths in the nanometer range are nature-based materials with unique and potentially useful features. Most importantly, these novel nanocelluloses open up the strongly expanding fields of sustainable materials and nanocomposites, as well as medical and life-science devices, to the natural polymer cellulose. The nanodimensions of the structural elements result in a high surface area and hence the powerful interaction of these celluloses with surrounding species. This Review assembles the current knowledge on the isolation of microfibrillated cellulose from wood and its application in nanocomposites; the prepn. of nanocryst. cellulose and its use as a reinforcing agent; and the biofabrication of bacterial nanocellulose, as well as its evaluation as a biomaterial for medical implants.
- 10Abitbol, T.; Rivkin, A.; Cao, Y.; Nevo, Y.; Abraham, E.; Ben-Shalom, T.; Lapidot, S.; Shoseyov, O. Nanocellulose, a Tiny Fiber with Huge Applications. Curr. Opin. Biotechnol. 2016, 39, 76– 88, DOI: 10.1016/j.copbio.2016.01.002Google Scholar10Nanocellulose, a tiny fiber with huge applicationsAbitbol, Tiffany; Rivkin, Amit; Cao, Yifeng; Nevo, Yuval; Abraham, Eldho; Ben-Shalom, Tal; Lapidot, Shaul; Shoseyov, OdedCurrent Opinion in Biotechnology (2016), 39 (), 76-88CODEN: CUOBE3; ISSN:0958-1669. (Elsevier B.V.)Nanocellulose is of increasing interest for a range of applications relevant to the fields of material science and biomedical engineering due to its renewable nature, anisotropic shape, excellent mech. properties, good biocompatibility, tailorable surface chem., and interesting optical properties. We discuss the main areas of nanocellulose research: photonics, films and foams, surface modifications, nanocomposites, and medical devices. These tiny nanocellulose fibers have huge potential in many applications, from flexible optoelectronics to scaffolds for tissue regeneration. We hope to impart the readers with some of the excitement that currently surrounds nanocellulose research, which arises from the green nature of the particles, their fascinating phys. and chem. properties, and the diversity of applications that can be impacted by this material.
- 11Kontturi, E.; Laaksonen, P.; Linder, M. B.; Nonappa; Gröschel, A. H.; Rojas, O. J.; Ikkala, O. Advanced Materials through Assembly of Nanocelluloses. Adv. Mater. 2018, 30, 1703779, DOI: 10.1002/adma.201703779Google ScholarThere is no corresponding record for this reference.
- 12Iwamoto, S.; Isogai, A.; Iwata, T. Structure and Mechanical Properties of Wet-Spun Fibers Made from Natural Cellulose Nanofibers. Biomacromolecules 2011, 12, 831– 836, DOI: 10.1021/bm101510rGoogle Scholar12Structure and mechanical properties of wet-spun fibers made from natural cellulose nanofibersIwamoto, Shinichiro; Isogai, Akira; Iwata, TadahisaBiomacromolecules (2011), 12 (3), 831-836CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)Cellulose nanofibers were prepd. by TEMPO-mediated oxidn. of wood pulp and tunicate cellulose. The cellulose nanofiber suspension in water was spun into an acetone coagulation bath. The spinning rate was varied from 0.1 to 100 m/min to align the nanofibers to the spun fibers. The fibers spun from the wood nanofibers had a hollow structure at spinning rates of >10 m/min, whereas the fibers spun from tunicate nanofibers were porous. Wide-angle X-ray diffraction anal. revealed that the wood and tunicate nanofibers were aligned to the fiber direction of the spun fibers at higher spinning rates. The wood spun fibers at 100 m/min had a Young's modulus of 23.6 GPa, tensile strength of 321 MPa, and elongation at break of 2.2%. The Young's modulus of the wood spun fibers increased with an increase in the spinning rate because of the nanofiber orientation effect.
- 13Walther, A.; Timonen, J. V. I.; Díez, I.; Laukkanen, A.; Ikkala, O. Multifunctional High-Performance Biofi Bers Based on Wet-Extrusion of Renewable Native Cellulose Nanofi Brils. Adv. Mater. 2011, 23, 2924– 2928, DOI: 10.1002/adma.201100580Google Scholar13Multifunctional High-Performance Biofibers Based on Wet-Extrusion of Renewable Native Cellulose NanofibrilsWalther, Andreas; Timonen, Jaakko V. I.; Diez, Isabel; Laukkanen, Antti; Ikkala, OlliAdvanced Materials (Weinheim, Germany) (2011), 23 (26), 2924-2928CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)The authors have developed a straightforward room-temp. process for functional macroscopic fibers and nonwovens based on native cellulose nanofibrils by simple wet extrusion, coagulation, and drying. The resulting NFC macrofibers demonstrate excellent mech. properties combining stiffness (22.5 GPa) and strength (275 MPa) with toughness (work of fracture 7.9 MJ m-3). The authors foresee that the properties can even be increased by a further alignment of the constituent NFC nanofibrils by post drawing processes. The authors have shown how to achieve transparent macrofibers and to control the water sorption by hydrophobization of the surface. The versatility of the wet-extrusion allows entrapping and immobilization of a multitude of functional mols. and payloads, either hydrophobic or hydrophilic, polymers, or even inorg. nanoparticles. The authors demonstrate these processes for model compds. (dyes), for the generation of biobased conducting fibers and externally actuable magnetic inorg./org. hybrid macrofibers. This combination of mech. strength and high degree of functionality render the materials a versatile platform for applications in materials and bio/life sciences. Considering the simplicity of the route and the sustainable character of nanocellulose, which is globally available in large quantities from plants (wood), the developed process is directly suitable for industrial-scale prodn. towards mech. robust, versatile, and renewable fiber materials with few recycling problems.
- 14Lundahl, M. J.; Cunha, A. G.; Rojo, E.; Papageorgiou, A. C.; Rautkari, L.; Arboleda, J. C.; Rojas, O. J. Strength and Water Interactions of Cellulose I Filaments Wet-Spun from Cellulose Nanofibril Hydrogels. Sci. Rep. 2016, 6, 30695, DOI: 10.1038/srep30695Google Scholar14Strength and Water Interactions of Cellulose I Filaments Wet-Spun from Cellulose Nanofibril HydrogelsLundahl, Meri J.; Cunha, A. Gisela; Rojo, Ester; Papageorgiou, Anastassios C.; Rautkari, Lauri; Arboleda, Julio C.; Rojas, Orlando J.Scientific Reports (2016), 6 (), 30695CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)Hydrogels comprising cellulose nanofibrils (CNF) were used in the synthesis of continuous filaments via wet-spinning. Hydrogel viscosity and spinnability, as well as orientation and strength of the spun filaments, were found to be strongly affected by the osmotic pressure as detd. by CNF surface charge and solid fraction in the spinning dope. The tensile strength, Young's modulus and degree of orientation (wide-angle X-ray scattering, WAXS) of filaments produced without drawing were 297 MPa, 21 GPa and 83%, resp., which are remarkable values. A thorough investigation of the interactions with water using dynamic vapor sorption (DVS) expts. revealed the role of sorption sites in the stability of the filaments in wet conditions. DVS anal. during cycles of relative humidity (RH) between 0 and 95% revealed major differences in water uptake by the filaments spun from hydrogels of different charge d. (CNF and TEMPO-oxidized CNF). It is concluded that the mech. performance of filaments in the presence of water deteriorates drastically by the same factors that facilitate fibril alignment and, consequently, enhance dry strength. For the most oriented filaments, the max. water vapor sorption at 95% RH was 39% based on dry wt.
- 15Ankerfors, M. Microfibrillated Cellulose: Energy-Efficient Preparation Techniques and Applications in Paper. PhD Thesis, KTH Royal Institute of Technology, 2015.Google ScholarThere is no corresponding record for this reference.
- 16Asaadi, S.; Hummel, M.; Hellsten, S.; Härkäsalmi, T.; Ma, Y.; Michud, A.; Sixta, H. Renewable High-Performance Fibers from the Chemical Recycling of Cotton Waste Utilizing an Ionic Liquid. ChemSusChem 2019, 9, 3250, DOI: 10.1002/cssc.201600680Google ScholarThere is no corresponding record for this reference.
- 17Lundahl, 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, 8– 19, DOI: 10.1021/acs.iecr.6b04010Google Scholar17Spinning of Cellulose Nanofibrils into Filaments: A ReviewLundahl, Meri J.; Klar, Ville; Wang, Ling; Ago, Mariko; Rojas, Orlando J.Industrial & Engineering Chemistry Research (2017), 56 (1), 8-19CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)Spinning of cellulose nanofibrils (CNF) offers promising opportunities to develop renewable fibers and filaments with strong, aligned structure. This review introduces recent findings on the relationship between the properties of CNF hydrogels, the spinning conditions and the performance of filaments obtained by dry- and wet-spinning. For example, the filament Young's modulus correlates with CNF structural factors, such as slenderness and crystallinity. Furthermore, high shear rates and extensional flow strengthen the filament, mainly by improving structural uniformity and partly by effectively orienting the fibrils. However, other less obvious factors, such as those assocd. with coagulation and drying, play crit. roles in filament performance. These and other details related to this timely application of CNF are presented here for the benefit of researchers and users of fibers and filaments for composites, textiles and others.
- 18Håkansson, 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, DOI: 10.1038/ncomms5018Google Scholar18Hydrodynamic alignment and assembly of nanofibrils resulting in strong cellulose filamentsHakansson Karl M O; Lundell Fredrik; Kvick Mathias; Prahl Wittberg Lisa; Fall Andreas B; Wagberg Lars; Yu Shun; Roth Stephan V; Santoro Gonzalo; Krywka Christina; Soderberg L DanielNature communications (2014), 5 (), 4018 ISSN:.Cellulose nanofibrils can be obtained from trees and have considerable potential as a building block for biobased materials. In order to achieve good properties of these materials, the nanostructure must be controlled. Here we present a process combining hydrodynamic alignment with a dispersion-gel transition that produces homogeneous and smooth filaments from a low-concentration dispersion of cellulose nanofibrils in water. The preferential fibril orientation along the filament direction can be controlled by the process parameters. The specific ultimate strength is considerably higher than previously reported filaments made of cellulose nanofibrils. The strength is even in line with the strongest cellulose pulp fibres extracted from wood with the same degree of fibril alignment. Successful nanoscale alignment before gelation demands a proper separation of the timescales involved. Somewhat surprisingly, the device must not be too small if this is to be achieved.
- 19Mittal, N.; Ansari, F.; Gowda, 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, 6378– 6388, DOI: 10.1021/acsnano.8b01084Google Scholar19Multiscale control of nanocellulose assembly: transferring remarkable nanoscale fibril mechanics to macroscale fibersMittal, Nitesh; Ansari, Farhan; Gowda. V, Krishne; Brouzet, Christophe; Chen, Pan; Larsson, Per Tomas; Roth, Stephan V.; Lundell, Fredrik; Waagberg, Lars; Kotov, Nicholas A.; Soederberg, L. DanielACS Nano (2018), 12 (7), 6378-6388CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Nanoscale building blocks of many materials exhibit extraordinary mech. properties due to their defect-free mol. structure. Translation of these high mech. properties to macroscopic materials represents a difficult materials engineering challenge due to the necessity to organize these building blocks into multiscale patterns and mitigate defects emerging at larger scales. Cellulose nanofibrils (CNFs), the most abundant structural element in living systems, has impressively high strength and stiffness, but natural or artificial cellulose composites are 3-15 times weaker than the CNFs. Here, we report the flow-assisted organization of CNFs into macroscale fibers with nearly perfect unidirectional alignment. Efficient stress transfer from macroscale to individual CNF due to crosslinking and high degree of order enables their Young's modulus to reach up to 86 GPa and a tensile strength of 1.57 GPa, exceeding the mech. properties of known natural or synthetic biopolymeric materials. The specific strength of our CNF fibers engineered at multiscale also exceeds that of metals, alloys, and glass fibers, enhancing the potential of sustainable lightwt. high-performance materials with multiscale self-organization.
- 20Mittal, N.; Jansson, R.; Widhe, M.; Benselfelt, T.; Håkansson, K. M. O.; Lundell, F.; Hedhammar, M.; Söderberg, L. D. Ultrastrong and Bioactive Nanostructured Bio-Based Composites. ACS Nano 2017, 11, 5148– 5159, DOI: 10.1021/acsnano.7b02305Google Scholar20Ultrastrong and Bioactive Nanostructured Bio-Based CompositesMittal, Nitesh; Jansson, Ronnie; Widhe, Mona; Benselfelt, Tobias; Haakansson, Karl M. O.; Lundell, Fredrik; Hedhammar, My; Soederberg, L. DanielACS Nano (2017), 11 (5), 5148-5159CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Nature's design of functional materials relies on smart combinations of simple components to achieve desired properties. Silk and cellulose are two clever examples from nature-spider silk being tough due to high extensibility, whereas cellulose possesses unparalleled strength and stiffness among natural materials. Unfortunately, silk proteins cannot be obtained in large quantities from spiders, and recombinant prodn. processes are so far rather expensive. We have therefore combined small amts. of functionalized recombinant spider silk proteins with the most abundant structural component on Earth (cellulose nanofibrils (CNFs)) to fabricate isotropic as well as anisotropic hierarchical structures. Our approach for the fabrication of bio-based anisotropic fibers results in previously unreached but highly desirable mech. performance with a stiffness of ∼55 GPa, strength at break of ∼1015 MPa, and toughness of ∼55 MJ m-3. We also show that addn. of small amts. of silk fusion proteins to CNF results in materials with advanced biofunctionalities, which cannot be anticipated for the wood-based CNF alone. These findings suggest that bio-based materials provide abundant opportunities to design composites with high strength and functionalities and bring down our dependence on fossil-based resources.
- 21Wang, L.; Ago, M.; Borghei, M.; Ishaq, A.; Papageorgiou, A. C.; Lundahl, M.; Rojas, O. J. Conductive Carbon Microfibers Derived from Wet-Spun Lignin/Nanocellulose Hydrogels. ACS Sustainable Chem. Eng. 2019, 7, 6013– 6022, DOI: 10.1021/acssuschemeng.8b06081Google Scholar21Conductive Carbon Microfibers Derived from Wet-Spun Lignin/Nanocellulose HydrogelsWang, Ling; Ago, Mariko; Borghei, Maryam; Ishaq, Amal; Papageorgiou, Anastassios C.; Lundahl, Meri; Rojas, Orlando J.ACS Sustainable Chemistry & Engineering (2019), 7 (6), 6013-6022CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)We introduce an eco-friendly process to dramatically simplify carbon microfiber fabrication from biobased materials. The microfibers are first produced by wet-spinning in aq. calcium chloride soln., which provides rapid coagulation of the hydrogel precursors comprising wood-derived lignin and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCNF). The thermomech. performance of the obtained lignin/TOCNF filaments is investigated as a function of cellulose nanofibril orientation (wide angle X-ray scattering (WAXS)), morphol., SEM, and d. Following direct carbonization of the filaments at 900 °C, carbon microfibers (CMFs) are obtained with remarkably high yield, up to 41%, at lignin loadings of 70 wt % in the precursor microfibers (compared to 23% yield for those produced in the absence of lignin). Without any thermal stabilization or graphitization steps, the morphol., strength, and flexibility of the CMFs are retained to a large degree compared to those of the resp. precursors. The elec. cond. of the CMFs reach values as high as 103 S cm-1, making them suitable for microelectrodes, fiber-shaped supercapacitors, and wearable electronics. Overall, the cellulose nanofibrils act as structural elements for fast, inexpensive, and environmentally sound wet-spinning while lignin endows CMFs with high carbon yield and elec. cond.
- 22Mertaniemi, H.; Escobedo-Lucea, C.; Sanz-Garcia, A.; Gandía, C.; Mäkitie, A.; Partanen, J.; Ikkala, O.; Yliperttula, M. Human Stem Cell Decorated Nanocellulose Threads for Biomedical Applications. Biomaterials 2016, 82, 208– 220, DOI: 10.1016/j.biomaterials.2015.12.020Google Scholar22Human stem cell decorated nanocellulose threads for biomedical applicationsMertaniemi, Henrikki; Escobedo-Lucea, Carmen; Sanz-Garcia, Andres; Gandia, Carolina; Makitie, Antti; Partanen, Jouni; Ikkala, Olli; Yliperttula, MarjoBiomaterials (2016), 82 (), 208-220CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)Upon surgery, local inflammatory reactions and postoperative infections cause complications, morbidity, and mortality. Delivery of human adipose mesenchymal stem cells (hASC) into the wounds is an efficient and safe means to reduce inflammation and promote wound healing. However, administration of stem cells by injection often results in low cell retention, and the cells deposit in other organs, reducing the efficiency of the therapy. Thus, it is essential to improve cell delivery to the target area using carriers to which the cells have a high affinity. Moreover, the application of hASC in surgery has typically relied on animal-origin components, which may induce immune reactions or even transmit infections due to pathogens. To solve these issues, we first show that native cellulose nanofibers (nanofibrillated cellulose, NFC) extd. from plants allow prepn. of glutaraldehyde cross-linked threads (NFC-X) with high mech. strength even under the wet cell culture or surgery conditions, characteristically challenging for cellulosic materials. Secondly, using a xenogeneic free protocol for isolation and maintenance of hASC, we demonstrate that cells adhere, migrate and proliferate on the NFC-X, even without surface modifiers. Cross-linked threads were not found to induce toxicity on the cells and, importantly, hASC attached on NFC-X maintained their undifferentiated state and preserved their bioactivity. After intradermal suturing with the hASC decorated NFC-X threads in an ex vivo expt., cells remained attached to the multifilament sutures without displaying morphol. changes or reducing their metabolic activity. Finally, as NFC-X optionally allows facile surface tailoring if needed, we anticipate that stem-cell-decorated NFC-X opens a versatile generic platform as a surgical bionanomaterial for fighting postoperative inflammation and chronic wound healing problems.
- 23Peng, F.; Zhang, L.; Wang, H.; Lv, P.; Yu, H. Sulfonated Carbon Nanotubes as a Strong Protonic Acid Catalyst. Carbon 2005, 43, 2405– 2408, DOI: 10.1016/j.carbon.2005.04.004Google Scholar23Sulfonated carbon nanotubes as a strong protonic acid catalystPeng, Feng; Zhang, Lei; Wang, Hongjuan; Lu, Ping; Yu, HaoCarbon (2005), 43 (11), 2405-2408CODEN: CRBNAH; ISSN:0008-6223. (Elsevier Ltd.)Sulfonated carbon nanotubes with a high d. of sulfonic acid groups were prepd. by reacting concd. sulfuric acid with multiwall carbon nanotubes at 250°. The carbon nanotubes are not oxidized, but are sulfonated, although concd. H2SO4 is a strongly oxidizing agent at high temps. SEM-EDS images reveal that the morphol. and structure of the carbon nanotubes did not change after sulfonation. It is suggested that the surface of the carbon nanotubes can be functionalized by -SO3H or -SO2NH2 groups, and the latter have good thermal stability at temps ≤500 K. A novel strong protonic acid catalyst is formed with high catalytic activity in esterification with a potential to replace unrecyclable and difficult to sep. "liq. acid" catalysts.
- 24Bristow, J. A.; Kolseth, P. Paper Structure and Properties; Dekker: New York, 1986.Google ScholarThere is no corresponding record for this reference.
- 25Wang, M.; Yu, D.-G.; Li, X.; Williams, G. R. The Development and Bio-Applications of Multifluid Electrospinning. Mater. Highlights 2020, 1, DOI: 10.2991/mathi.k.200521.001Google ScholarThere is no corresponding record for this reference.
Cited By
Click to copy section linkSection link copied!
Citation Statements
beta
Smart citations by scite.ai include citation statements extracted from the full text of the citing article. The number of the statements may be higher than the number of citations provided by ACS Publications if one paper cites another multiple times or lower if scite has not yet processed some of the citing articles.
Explore this article's citation statements on scite.ai
This article is cited by 25 publications.
- Junqi Gao, Hui Mao, Yuying Kong, Zihuan Zhang, Khak Ho Lim, Wen-Jun Wang, Xuan Yang. The Effect of Nanocellulose Surface Properties on the Corresponding Wet-Spinning Process for Man-Made Fibers: Extrusion, Coagulation, and Drying. Industrial & Engineering Chemistry Research 2024, 63
(49)
, 21312-21322. https://doi.org/10.1021/acs.iecr.4c02979
- Chunyan Xu, Xiaoyan Zhao, Chenyi Wang, Xiao Zhu, Hengxue Xiang. Hollow Fiber Sensors with a Turn-On Fluorescence Response, Recycling, and Water Proofing for Monitoring Benzene Series. ACS Applied Polymer Materials 2024, 6
(16)
, 9794-9805. https://doi.org/10.1021/acsapm.4c01650
- Mingbo Sun, Teng Hou, Jing Zhou, Lele Zhou, Zhao Zhang, Xianglong Li, Bin Yang. Nanofibers with an Adjustable Core-Sheath Structure Constructed from Hyperbranched Polyester for Efficient Loading of ZnO Nanoparticles. ACS Applied Nano Materials 2023, 6
(11)
, 9707-9717. https://doi.org/10.1021/acsanm.3c01386
- Andreas B. Fall, Farnaz Hagel, Jesper Edberg, Abdellah Malti, Per A. Larsson, Lars Wågberg, Hjalmar Granberg, Karl M. O. Håkansson. Spinning of Stiff and Conductive Filaments from Cellulose Nanofibrils and PEDOT:PSS Nanocomplexes. ACS Applied Polymer Materials 2022, 4
(6)
, 4119-4130. https://doi.org/10.1021/acsapm.2c00073
- Qihua Li, Zhanhong Yuan, Chi Zhang, Shuiqing Hu, Zhiming Chen, Yingzhu Wu, Pan Chen, Haisong Qi, Dongdong Ye. Tough, Highly Oriented, Super Thermal Insulating Regenerated All-Cellulose Sponge-Aerogel Fibers Integrating a Graded Aligned Nanostructure. Nano Letters 2022, 22
(9)
, 3516-3524. https://doi.org/10.1021/acs.nanolett.1c03943
- Guillermo Reyes, Rubina Ajdary, Maryam R. Yazdani, Orlando J. Rojas. Hollow Filaments Synthesized by Dry-Jet Wet Spinning of Cellulose Nanofibrils: Structural Properties and Thermoregulation with Phase-Change Infills. ACS Applied Polymer Materials 2022, 4
(4)
, 2908-2916. https://doi.org/10.1021/acsapm.2c00177
- Pooja Agarwal, Subhalaxmi Pradhan, Divya Bajpai Tripathy. Electrospun nanofibers for water remediation: Functionalization, structural innovations, and mechanistic insights. Desalination 2025, 613 , 119086. https://doi.org/10.1016/j.desal.2025.119086
- Yu‐Xiao Shi, Ya‐Jiao Zhu, Zhi‐Gang Qian, Xiao‐Xia Xia. Artificial Spider Silk Materials: From Molecular Design, Mesoscopic Assembly, to Macroscopic Performances. Advanced Functional Materials 2025, 35
(15)
https://doi.org/10.1002/adfm.202412793
- Wenjiang Lu, Qixuan Deng, Minsu Liu, Baofu Ding, Zhiyuan Xiong, Ling Qiu. Coaxial Wet Spinning of Boron Nitride Nanosheet-Based Composite Fibers with Enhanced Thermal Conductivity and Mechanical Strength. Nano-Micro Letters 2024, 16
(1)
https://doi.org/10.1007/s40820-023-01236-w
- Kang Yang, Chao Duan, Ruoteng Ma, Xiaoshuang Liu, Zixuan Meng, Zengyin Xie, Yonghao Ni. Smart and robust phase change cellulose fibers from coaxial wet-spinning of cellulose nanofibril-reinforced paraffin capsules with excellent thermal management. Carbohydrate Polymers 2024, 346 , 122649. https://doi.org/10.1016/j.carbpol.2024.122649
- Meiyan Wu, Lei Ding, Xiaoying Bai, Yuxiang Cao, Mehdi Rahmaninia, Bing Li, Bin Li. Cellulose-based suture: State of art, challenge, and future outlook. Journal of Bioresources and Bioproducts 2024, 29 https://doi.org/10.1016/j.jobab.2024.11.006
- Nadia Asta, Maximilian Loist, Michael S. Reid, Lars Wågberg. Model systems for clarifying the effects of surface modification on fibre–fibre joint strength and paper mechanical properties. Cellulose 2024, 31
(14)
, 8465-8478. https://doi.org/10.1007/s10570-024-06103-4
- Benjamin Schmuck, Gabriele Greco, Tomas Bohn Pessatti, Sumalata Sonavane, Viktoria Langwallner, Tina Arndt, Anna Rising. Strategies for Making High‐Performance Artificial Spider Silk Fibers. Advanced Functional Materials 2024, 34
(35)
https://doi.org/10.1002/adfm.202305040
- Zihuan Zhang, Yuying Kong, Junqi Gao, Xiao Han, Zechun Lian, Jiamin Liu, Wen-Jun Wang, Xuan Yang. Engineering strong man-made cellulosic fibers: a review of the wet spinning process based on cellulose nanofibrils. Nanoscale 2024, 16
(13)
, 6383-6401. https://doi.org/10.1039/D3NR06126D
- Eduardo Espinosa, Laura M. Sanchez, Zoilo González, Achmad Himawan, Alejandro Rodríguez. Nanocellulose-based filaments: production, characterization, and applications. 2024, 93-116. https://doi.org/10.1016/B978-0-443-18608-0.00020-6
- Minhu Huang, Seunghyeon Lee, Il-Young Jo, Hyunbeen Park, Bong Sup Shim, Myung-Han Yoon. One-step wet-spinning of conducting polymer and cellulose nanofiber composites for fiber-type organic electrochemical transistors. Carbohydrate Polymers 2024, 324 , 121559. https://doi.org/10.1016/j.carbpol.2023.121559
- Ning Ren, Aihua Qiao, Mei Cui, Renliang Huang, Wei Qi, Rongxin Su. Design and fabrication of nanocellulose-based microfibers by wet spinning. Chemical Engineering Science 2023, 282 , 119320. https://doi.org/10.1016/j.ces.2023.119320
- Wentao Cao, Xinyu Zhao, Bingqiang Lu, Daxiang Cui, Feng Chen. Assembly of Nanowires into Macroscopic One-Dimensional Fibers in Liquid State. Advanced Fiber Materials 2023, 5
(3)
, 928-954. https://doi.org/10.1007/s42765-023-00265-9
- Song Wei, Caichao Wan, Yiqiang Wu. Recent advances in wood-based electrode materials for supercapacitors. Green Chemistry 2023, 25
(9)
, 3322-3353. https://doi.org/10.1039/D2GC04271A
- Meiyan Wu, Yinuo Liu, Chao Liu, Qiu Cui, Xin Zheng, Pedram Fatehi, Bin Li. Core–Shell Filament with Excellent Wound Healing Property Made of Cellulose Nanofibrils and Guar Gum via Interfacial Polyelectrolyte Complexation Spinning. Small 2023, 19
(4)
https://doi.org/10.1002/smll.202205867
- Changxiu Chen, Panyi Xi, Liming Zhang, Yaning Sun, Jiuyong Yao, Kuanjun Fang, Yanzhi Xia, Yijun Jiang. A strategy to fabricate tough and strong bioinspired fiber with asymmetric structure and water-driven performance. Composites Science and Technology 2022, 224 , 109464. https://doi.org/10.1016/j.compscitech.2022.109464
- Weiheng Xu, Sayli Jambhulkar, Dharneedar Ravichandran, Yuxiang Zhu, Shantanu Lanke, Mohammed Bawareth, Kenan Song. A mini‐review of microstructural control during composite fiber spinning. Polymer International 2022, 71
(5)
, 569-577. https://doi.org/10.1002/pi.6350
- Xingchun Zhao, Shiyan Chen, Zhuotong Wu, Nan Sheng, Minghao Zhang, Qianqian Liang, Zhiliang Han, Huaping Wang. Toward continuous high-performance bacterial cellulose macrofibers by implementing grading-stretching in spinning. Carbohydrate Polymers 2022, 282 , 119133. https://doi.org/10.1016/j.carbpol.2022.119133
- Adel Mohammed Al-Dhahebi, JinKiong Ling, Syam G. Krishnan, Maryam Yousefzadeh, Naveen Kumar Elumalai, Mohamed Shuaib Mohamed Saheed, Seeram Ramakrishna, Rajan Jose. Electrospinning research and products: The road and the way forward. Applied Physics Reviews 2022, 9
(1)
https://doi.org/10.1063/5.0077959
- Qian Gao, Jiabao Wang, Jing Liu, Yuda Wang, Jinge Guo, Ziyi Zhong, Xinliang Liu. High mechanical performance based on the alignment of cellulose nanocrystal/chitosan composite filaments through continuous coaxial wet spinning. Cellulose 2021, 28
(12)
, 7995-8008. https://doi.org/10.1007/s10570-021-04009-z
Learn about these metrics
Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.
Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.
The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated.
Recommended Articles
Abstract
Figure 1
Figure 1. (a) Schematic depicting the process of coaxial filament spinning using CNF in the core flow and HCl (pH 2) in the sheath flow (not to scale), (b) 3D schematic of the coaxial extrusion setup showing the flow contraction, (c) photograph of the extrusion of filaments in the extrusion bath (for enhanced contrast, a CNF/CNT black suspension was used (scale bar: 1 cm), (d) photograph of a wet filament (scale bar: 1 cm), (e) optical microscope images of a CNF filament during drying at ambient temperature and RH taken at 2 min interval, showing the diameter reduction and formation of surface mesoscale structures (scale bar: 100 μm).
Figure 2
Figure 2. SEM images of CNF filaments showing (a,b) their surface and (c) cross section. Scale bars are 10, 2,and 5 μm, respectively. (d) WAXS diffractogram (scale bar 5 nm–1) and the related (e) radial and (f) azimuthal integration.
Figure 3
Figure 3. Tensile stress/strain testing of CNF filaments. Inset depicts the sample preparation/fixation where the filaments are glued on a paper frame in order to minimize the pretesting stress.
Figure 4
Figure 4. Coaxial core (CNF)/shell (sCNT) filaments: (a) Schematic depicting the principle and chemical composition of the core and sheath flows, (b) SEM picture of the cross section (scale bar: 5 μm) and (c) inset showing the interface between the CNF core and sCNT shell (scale bar: 500 nm), (d) cyclic voltammogram recorded at a scan rate of 10 mV s–1 in 1 M KCl, and (e) galvanostatic cycling.
Figure 5
Figure 5. (a) SEM picture of a coaxial core (CNF)/shell (MMT) filament (scale bars, 10 μm; inset, 3 μm) and (b) its cross section showing the distinct layers of MMT on the CNF core (scale bars, 5 μm; inset, 1 μm).
References
This article references 25 other publications.
- 1Ling, S.; Kaplan, D. L.; Buehler, M. J. Nanofibrils in Nature and Materials Engineering. Nat. Rev. Mater. 2018, 3, 18016, DOI: 10.1038/natrevmats.2018.161Nanofibrils in nature and materials engineeringLing, Shengjie; Kaplan, David L.; Buehler, Markus J.Nature Reviews Materials (2018), 3 (4), 18016CODEN: NRMADL; ISSN:2058-8437. (Nature Research)Nanofibrillar materials, such as cellulose, chitin and silk, are highly ordered architectures, formed through the self-assembly of repetitive building blocks into higher-order structures, which are stabilized by non-covalent interactions. This hierarchical building principle endows many biol. materials with remarkable mech. strength, anisotropy, flexibility and optical properties, such as structural color. These features make nanofibrillar biopolymers interesting candidates for the development of strong, sustainable and biocompatible materials for environmental, energy, optical and biomedical applications. However, recreating their architecture is challenging from an engineering perspective. Rational design approaches, applying a combination of theor. and exptl. protocols, have enabled the design of biopolymer-based materials through mimicking natures multiscale assembly approach. In this Review, we summarize hierarchical design strategies of cellulose, silk and chitin, focusing on nanoconfinement, fibrillar orientation and alignment in 2D and 3D structures. These multiscale architectures are discussed in the context of mech. and optical properties, and different fabrication strategies for the manufg. of biopolymer nanofibril-based materials are investigated. We highlight the contribution of rational material design strategies to the development of mech. anisotropic and responsive materials and examine the future of the material-by-design paradigm.
- 2Dufresne, A. Nanocellulose: A New Ageless Bionanomaterial. Mater. Today 2013, 16, 220– 227, DOI: 10.1016/j.mattod.2013.06.0042Nanocellulose: a new ageless bionanomaterialDufresne, AlainMaterials Today (Oxford, United Kingdom) (2013), 16 (6), 220-227CODEN: MTOUAN; ISSN:1369-7021. (Elsevier Ltd.)A review. Owing to the hierarchical structure of cellulose, nanoparticles can be extd. from this naturally occurring polymer. Multiple mech. shearing actions allow the release of more or fewer individual microfibrils. Longitudinal cutting of these microfibrils can be achieved by a strong acid hydrolysis treatment, allowing dissoln. of amorphous domains. The impressive mech. properties, reinforcing capabilities, abundance, low d., and biodegradability of these nanoparticles make them ideal candidates for the processing of polymer nanocomposites. With a Young's modulus in the range 100-130 GPa and a surface area of several hundred m2 g-1, new promising properties can be considered for cellulose.
- 3Wågberg, L.; Decher, G.; Norgren, M.; Lindström, T.; Ankerfors, M.; Axnäs, K. The Build-up of Polyelectrolyte Multilayers of Microfibrillated Cellulose and Cationic Polyelectrolytes. Langmuir 2008, 24, 784– 795, DOI: 10.1021/la702481v3The build-up of polyelectrolyte multilayers of microfibrillated cellulose and cationic polyelectrolytesWagberg Lars; Decher Gero; Norgren Magnus; Lindstrom Tom; Ankerfors Mikael; Axnas KarlLangmuir : the ACS journal of surfaces and colloids (2008), 24 (3), 784-95 ISSN:0743-7463.A new type of nanocellulosic material has been prepared by high-pressure homogenization of carboxymethylated cellulose fibers followed by ultrasonication and centrifugation. This material had a cylindrical cross-section as shown by transmission electron microscopy with a diameter of 5-15 nm and a length of up to 1 microm. Calculations, using the Poisson-Boltzmann equation, showed that the surface potential was between 200 and 250 mV, depending on the pH, the salt concentration, and the size of the fibrils. They also showed that the carboxyl groups on the surface of the nanofibrils are not fully dissociated until the pH has reached pH = approximately 10 in deionized water. Calculations of the interaction between the fibrils using the Derjaguin-Landau-Verwey-Overbeek theory and assuming a cylindrical geometry indicated that there is a large electrostatic repulsion between these fibrils, provided the carboxyl groups are dissociated. If the pH is too low and/or the salt concentration is too high, there will be a large attraction between the fibrils, leading to a rapid aggregation of the fibrils. It is also possible to form polyelectrolyte multilayers (PEMs) by combining different types of polyelectrolytes and microfibrillated cellulose (MFC). In this study, silicon oxide surfaces were first treated with cationic polyelectrolytes before the surfaces were exposed to MFC. The build-up of the layers was monitored with ellipsometry, and they show that it is possible to form very well-defined layers by combinations of MFC and different types of polyelectrolytes and different ionic strengths of the solutions during the adsorption of the polyelectrolyte. A polyelectrolyte with a three-dimensional structure leads to the build-up of thick layers of MFC, whereas the use of a highly charged linear polyelectrolyte leads to the formation of thinner layers of MFC. An increase in the salt concentration during the adsorption of the polyelectrolyte results in the formation of thicker layers of MFC, indicating that the structure of the adsorbed polyelectrolyte has a large influence on the formation of the MFC layer. The films of polyelectrolytes and MFC were so smooth and well-defined that they showed clearly different interference colors, depending on the film thickness. A comparison between the thickness of the films, as measured with ellipsometry, and the thickness estimated from their colors showed good agreement, assuming that the films consisted mainly of solid cellulose with a refractive index of 1.53. Carboxymethylated MFC is thus a new type of nanomaterial that can be combined with oppositely charged polyelectrolytes to form well-defined layers that may be used to form, for example, new types of sensor materials.
- 4Saito, T.; Kimura, S.; Nishiyama, Y.; Isogai, A. Cellulose Nanofibers Prepared by TEMPO-Mediated Oxidation of Native Cellulose. Biomacromolecules 2007, 8, 2485– 2491, DOI: 10.1021/bm07039704Cellulose Nanofibers Prepared by TEMPO-Mediated Oxidation of Native CelluloseSaito, Tsuguyuki; Kimura, Satoshi; Nishiyama, Yoshiharu; Isogai, AkiraBiomacromolecules (2007), 8 (8), 2485-2491CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)Never-dried and once-dried hardwood celluloses were oxidized by a 2,2,6,6-tetra-Me piperidine-1-oxyl radical (TEMPO)-mediated system, and highly cryst. and individualized cellulose nanofibers, dispersed in water, were prepd. by mech. treatment of the oxidized cellulose/water slurries. When carboxylate contents formed from the primary hydroxyl groups of the celluloses reached approx. 1.5 mmol/g, the oxidized cellulose/water slurries were mostly converted to transparent and highly viscous dispersions by mech. treatment. Transmission electron microscopic observation showed that the dispersions consisted of individualized cellulose nanofibers 3-4 nm in width and a few microns in length. No intrinsic differences between never-dried and once-dried celluloses were found for prepg. the dispersion, as long as carboxylate contents in the TEMPO-oxidized celluloses reached approx. 1.5 mmol/g. Changes in viscosity of the dispersions during the mech. treatment corresponded with those in the dispersed states of the cellulose nanofibers in water.
- 5Eichhorn, S. J.; Dufresne, A.; Aranguren, M.; Marcovich, N. E.; Capadona, J. R.; Rowan, S. J.; Weder, C.; Thielemans, W.; Roman, M.; Renneckar, S.; Gindl, W.; Veigel, S.; Keckes, J.; Yano, H.; Abe, K.; Nogi, M.; Nakagaito, A. N.; Mangalam, A.; Simonsen, J.; Benight, A. S.; Bismarck, A.; Berglund, L. A.; Peijs, T. Review: Current International Research into Cellulose Nanofibres and Nanocomposites. J. Mater. Sci. 2009, 45, 1– 33, DOI: 10.1007/s10853-009-3874-0There is no corresponding record for this reference.
- 6Nordenström, M.; Fall, A.; Nyström, G.; Wågberg, L. Formation of Colloidal Nanocellulose Glasses and Gels. Langmuir 2017, 33, 9772– 9780, DOI: 10.1021/acs.langmuir.7b018326Formation of Colloidal Nanocellulose Glasses and GelsNordenstrom Malin; Fall Andreas; Wagberg Lars; Nystrom GustavLangmuir : the ACS journal of surfaces and colloids (2017), 33 (38), 9772-9780 ISSN:.Nanocellulose (NC) suspensions can form rigid volume-spanning arrested states (VASs) at very low volume fractions. The transition from a free-flowing dispersion to a VAS can be the result of either an increase in particle concentration or a reduction in interparticle repulsion. In this work, the concentration-induced transition has been studied with a special focus on the influence of the particle aspect ratio and surface charge density, and an attempt is made to classify these VASs. The results show that for these types of systems two general states can be identified: glasses and gels. These NC suspensions had threshold concentrations inversely proportional to the particle aspect ratio. This dependence indicates that the main reason for the transition is a mobility constraint that, together with the reversibility of the transition, classifies the VASs as colloidal glasses. If the interparticle repulsion is reduced, then the glasses can transform into gels. Thus, depending on the preparation route, either soft and reversible glasses or stiff and irreversible gels can be formed.
- 7Fall, A. B.; Lindström, S. B.; Sundman, O.; Ödberg, L.; Wågberg, L. Colloidal Stability of Aqueous Nanofibrillated Cellulose Dispersions. Langmuir 2011, 27, 11332– 11338, DOI: 10.1021/la201947x7Colloidal Stability of Aqueous Nanofibrillated Cellulose DispersionsFall, Andreas B.; Lindstroem, Stefan B.; Sundman, Ola; Oedberg, Lars; Waagberg, LarsLangmuir (2011), 27 (18), 11332-11338CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)Cellulose nanofibrils constitute an attractive raw material for carbon-neutral, biodegradable, nanostructured materials. Aq. suspensions of these nanofibrils are stabilized by electrostatic repulsion arising from deprotonated carboxyl groups at the fibril surface. In the present work, a new model is developed for predicting colloidal stability by considering deprotonation and electrostatic screening. This model predicts the fibril-fibril interaction potential at a given pH in a given ionic strength environment. Expts. support the model predictions that aggregation is induced by decreasing the pH, thus reducing the surface charge, or by increasing the salt concn. It is shown that the primary mechanism for aggregation upon the addn. of salt is the surface charge redn. through specific interactions of counterions with the deprotonated carboxyl groups, and the screening effect of the salt is of secondary importance.
- 8Lavoine, N.; Desloges, I.; Dufresne, A.; Bras, J. Microfibrillated Cellulose - Its Barrier Properties and Applications in Cellulosic Materials: A Review. Carbohydr. Polym. 2012, 90, 735– 764, DOI: 10.1016/j.carbpol.2012.05.0268Microfibrillated cellulose - Its barrier properties and applications in cellulosic materials: A reviewLavoine, Nathalie; Desloges, Isabelle; Dufresne, Alain; Bras, JulienCarbohydrate Polymers (2012), 90 (2), 735-764CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)A review. Interest in microfibrillated cellulose (MFC) has been increasing exponentially. Its nano-scale dimensions and its ability to form a strong nanoporous network have encouraged the emergence of new high-value applications. The nanoscale characterization possibilities of different MFC materials are thus increasing intensively. Therefore, it is crit. to review such MFC materials and their properties. Moreover, very recent studies have proved the significant barrier properties of MFC (e.g., decrease of water vapor permeability).
- 9Klemm, D.; Kramer, F.; Moritz, S.; Lindström, T.; Ankerfors, M.; Gray, D.; Dorris, A. Nanocelluloses: A New Family of Nature-Based Materials. Angew. Chem. 2011, 50, 5438– 5466, DOI: 10.1002/anie.2010012739Nanocelluloses: A New Family of Nature-Based MaterialsKlemm, Dieter; Kramer, Friederike; Moritz, Sebastian; Lindstroem, Tom; Ankerfors, Mikael; Gray, Derek; Dorris, AnnieAngewandte Chemie, International Edition (2011), 50 (24), 5438-5466CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)A review. Cellulose fibrils with widths in the nanometer range are nature-based materials with unique and potentially useful features. Most importantly, these novel nanocelluloses open up the strongly expanding fields of sustainable materials and nanocomposites, as well as medical and life-science devices, to the natural polymer cellulose. The nanodimensions of the structural elements result in a high surface area and hence the powerful interaction of these celluloses with surrounding species. This Review assembles the current knowledge on the isolation of microfibrillated cellulose from wood and its application in nanocomposites; the prepn. of nanocryst. cellulose and its use as a reinforcing agent; and the biofabrication of bacterial nanocellulose, as well as its evaluation as a biomaterial for medical implants.
- 10Abitbol, T.; Rivkin, A.; Cao, Y.; Nevo, Y.; Abraham, E.; Ben-Shalom, T.; Lapidot, S.; Shoseyov, O. Nanocellulose, a Tiny Fiber with Huge Applications. Curr. Opin. Biotechnol. 2016, 39, 76– 88, DOI: 10.1016/j.copbio.2016.01.00210Nanocellulose, a tiny fiber with huge applicationsAbitbol, Tiffany; Rivkin, Amit; Cao, Yifeng; Nevo, Yuval; Abraham, Eldho; Ben-Shalom, Tal; Lapidot, Shaul; Shoseyov, OdedCurrent Opinion in Biotechnology (2016), 39 (), 76-88CODEN: CUOBE3; ISSN:0958-1669. (Elsevier B.V.)Nanocellulose is of increasing interest for a range of applications relevant to the fields of material science and biomedical engineering due to its renewable nature, anisotropic shape, excellent mech. properties, good biocompatibility, tailorable surface chem., and interesting optical properties. We discuss the main areas of nanocellulose research: photonics, films and foams, surface modifications, nanocomposites, and medical devices. These tiny nanocellulose fibers have huge potential in many applications, from flexible optoelectronics to scaffolds for tissue regeneration. We hope to impart the readers with some of the excitement that currently surrounds nanocellulose research, which arises from the green nature of the particles, their fascinating phys. and chem. properties, and the diversity of applications that can be impacted by this material.
- 11Kontturi, E.; Laaksonen, P.; Linder, M. B.; Nonappa; Gröschel, A. H.; Rojas, O. J.; Ikkala, O. Advanced Materials through Assembly of Nanocelluloses. Adv. Mater. 2018, 30, 1703779, DOI: 10.1002/adma.201703779There is no corresponding record for this reference.
- 12Iwamoto, S.; Isogai, A.; Iwata, T. Structure and Mechanical Properties of Wet-Spun Fibers Made from Natural Cellulose Nanofibers. Biomacromolecules 2011, 12, 831– 836, DOI: 10.1021/bm101510r12Structure and mechanical properties of wet-spun fibers made from natural cellulose nanofibersIwamoto, Shinichiro; Isogai, Akira; Iwata, TadahisaBiomacromolecules (2011), 12 (3), 831-836CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)Cellulose nanofibers were prepd. by TEMPO-mediated oxidn. of wood pulp and tunicate cellulose. The cellulose nanofiber suspension in water was spun into an acetone coagulation bath. The spinning rate was varied from 0.1 to 100 m/min to align the nanofibers to the spun fibers. The fibers spun from the wood nanofibers had a hollow structure at spinning rates of >10 m/min, whereas the fibers spun from tunicate nanofibers were porous. Wide-angle X-ray diffraction anal. revealed that the wood and tunicate nanofibers were aligned to the fiber direction of the spun fibers at higher spinning rates. The wood spun fibers at 100 m/min had a Young's modulus of 23.6 GPa, tensile strength of 321 MPa, and elongation at break of 2.2%. The Young's modulus of the wood spun fibers increased with an increase in the spinning rate because of the nanofiber orientation effect.
- 13Walther, A.; Timonen, J. V. I.; Díez, I.; Laukkanen, A.; Ikkala, O. Multifunctional High-Performance Biofi Bers Based on Wet-Extrusion of Renewable Native Cellulose Nanofi Brils. Adv. Mater. 2011, 23, 2924– 2928, DOI: 10.1002/adma.20110058013Multifunctional High-Performance Biofibers Based on Wet-Extrusion of Renewable Native Cellulose NanofibrilsWalther, Andreas; Timonen, Jaakko V. I.; Diez, Isabel; Laukkanen, Antti; Ikkala, OlliAdvanced Materials (Weinheim, Germany) (2011), 23 (26), 2924-2928CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)The authors have developed a straightforward room-temp. process for functional macroscopic fibers and nonwovens based on native cellulose nanofibrils by simple wet extrusion, coagulation, and drying. The resulting NFC macrofibers demonstrate excellent mech. properties combining stiffness (22.5 GPa) and strength (275 MPa) with toughness (work of fracture 7.9 MJ m-3). The authors foresee that the properties can even be increased by a further alignment of the constituent NFC nanofibrils by post drawing processes. The authors have shown how to achieve transparent macrofibers and to control the water sorption by hydrophobization of the surface. The versatility of the wet-extrusion allows entrapping and immobilization of a multitude of functional mols. and payloads, either hydrophobic or hydrophilic, polymers, or even inorg. nanoparticles. The authors demonstrate these processes for model compds. (dyes), for the generation of biobased conducting fibers and externally actuable magnetic inorg./org. hybrid macrofibers. This combination of mech. strength and high degree of functionality render the materials a versatile platform for applications in materials and bio/life sciences. Considering the simplicity of the route and the sustainable character of nanocellulose, which is globally available in large quantities from plants (wood), the developed process is directly suitable for industrial-scale prodn. towards mech. robust, versatile, and renewable fiber materials with few recycling problems.
- 14Lundahl, M. J.; Cunha, A. G.; Rojo, E.; Papageorgiou, A. C.; Rautkari, L.; Arboleda, J. C.; Rojas, O. J. Strength and Water Interactions of Cellulose I Filaments Wet-Spun from Cellulose Nanofibril Hydrogels. Sci. Rep. 2016, 6, 30695, DOI: 10.1038/srep3069514Strength and Water Interactions of Cellulose I Filaments Wet-Spun from Cellulose Nanofibril HydrogelsLundahl, Meri J.; Cunha, A. Gisela; Rojo, Ester; Papageorgiou, Anastassios C.; Rautkari, Lauri; Arboleda, Julio C.; Rojas, Orlando J.Scientific Reports (2016), 6 (), 30695CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)Hydrogels comprising cellulose nanofibrils (CNF) were used in the synthesis of continuous filaments via wet-spinning. Hydrogel viscosity and spinnability, as well as orientation and strength of the spun filaments, were found to be strongly affected by the osmotic pressure as detd. by CNF surface charge and solid fraction in the spinning dope. The tensile strength, Young's modulus and degree of orientation (wide-angle X-ray scattering, WAXS) of filaments produced without drawing were 297 MPa, 21 GPa and 83%, resp., which are remarkable values. A thorough investigation of the interactions with water using dynamic vapor sorption (DVS) expts. revealed the role of sorption sites in the stability of the filaments in wet conditions. DVS anal. during cycles of relative humidity (RH) between 0 and 95% revealed major differences in water uptake by the filaments spun from hydrogels of different charge d. (CNF and TEMPO-oxidized CNF). It is concluded that the mech. performance of filaments in the presence of water deteriorates drastically by the same factors that facilitate fibril alignment and, consequently, enhance dry strength. For the most oriented filaments, the max. water vapor sorption at 95% RH was 39% based on dry wt.
- 15Ankerfors, M. Microfibrillated Cellulose: Energy-Efficient Preparation Techniques and Applications in Paper. PhD Thesis, KTH Royal Institute of Technology, 2015.There is no corresponding record for this reference.
- 16Asaadi, S.; Hummel, M.; Hellsten, S.; Härkäsalmi, T.; Ma, Y.; Michud, A.; Sixta, H. Renewable High-Performance Fibers from the Chemical Recycling of Cotton Waste Utilizing an Ionic Liquid. ChemSusChem 2019, 9, 3250, DOI: 10.1002/cssc.201600680There is no corresponding record for this reference.
- 17Lundahl, 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, 8– 19, DOI: 10.1021/acs.iecr.6b0401017Spinning of Cellulose Nanofibrils into Filaments: A ReviewLundahl, Meri J.; Klar, Ville; Wang, Ling; Ago, Mariko; Rojas, Orlando J.Industrial & Engineering Chemistry Research (2017), 56 (1), 8-19CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)Spinning of cellulose nanofibrils (CNF) offers promising opportunities to develop renewable fibers and filaments with strong, aligned structure. This review introduces recent findings on the relationship between the properties of CNF hydrogels, the spinning conditions and the performance of filaments obtained by dry- and wet-spinning. For example, the filament Young's modulus correlates with CNF structural factors, such as slenderness and crystallinity. Furthermore, high shear rates and extensional flow strengthen the filament, mainly by improving structural uniformity and partly by effectively orienting the fibrils. However, other less obvious factors, such as those assocd. with coagulation and drying, play crit. roles in filament performance. These and other details related to this timely application of CNF are presented here for the benefit of researchers and users of fibers and filaments for composites, textiles and others.
- 18Håkansson, 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, DOI: 10.1038/ncomms501818Hydrodynamic alignment and assembly of nanofibrils resulting in strong cellulose filamentsHakansson Karl M O; Lundell Fredrik; Kvick Mathias; Prahl Wittberg Lisa; Fall Andreas B; Wagberg Lars; Yu Shun; Roth Stephan V; Santoro Gonzalo; Krywka Christina; Soderberg L DanielNature communications (2014), 5 (), 4018 ISSN:.Cellulose nanofibrils can be obtained from trees and have considerable potential as a building block for biobased materials. In order to achieve good properties of these materials, the nanostructure must be controlled. Here we present a process combining hydrodynamic alignment with a dispersion-gel transition that produces homogeneous and smooth filaments from a low-concentration dispersion of cellulose nanofibrils in water. The preferential fibril orientation along the filament direction can be controlled by the process parameters. The specific ultimate strength is considerably higher than previously reported filaments made of cellulose nanofibrils. The strength is even in line with the strongest cellulose pulp fibres extracted from wood with the same degree of fibril alignment. Successful nanoscale alignment before gelation demands a proper separation of the timescales involved. Somewhat surprisingly, the device must not be too small if this is to be achieved.
- 19Mittal, N.; Ansari, F.; Gowda, 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, 6378– 6388, DOI: 10.1021/acsnano.8b0108419Multiscale control of nanocellulose assembly: transferring remarkable nanoscale fibril mechanics to macroscale fibersMittal, Nitesh; Ansari, Farhan; Gowda. V, Krishne; Brouzet, Christophe; Chen, Pan; Larsson, Per Tomas; Roth, Stephan V.; Lundell, Fredrik; Waagberg, Lars; Kotov, Nicholas A.; Soederberg, L. DanielACS Nano (2018), 12 (7), 6378-6388CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Nanoscale building blocks of many materials exhibit extraordinary mech. properties due to their defect-free mol. structure. Translation of these high mech. properties to macroscopic materials represents a difficult materials engineering challenge due to the necessity to organize these building blocks into multiscale patterns and mitigate defects emerging at larger scales. Cellulose nanofibrils (CNFs), the most abundant structural element in living systems, has impressively high strength and stiffness, but natural or artificial cellulose composites are 3-15 times weaker than the CNFs. Here, we report the flow-assisted organization of CNFs into macroscale fibers with nearly perfect unidirectional alignment. Efficient stress transfer from macroscale to individual CNF due to crosslinking and high degree of order enables their Young's modulus to reach up to 86 GPa and a tensile strength of 1.57 GPa, exceeding the mech. properties of known natural or synthetic biopolymeric materials. The specific strength of our CNF fibers engineered at multiscale also exceeds that of metals, alloys, and glass fibers, enhancing the potential of sustainable lightwt. high-performance materials with multiscale self-organization.
- 20Mittal, N.; Jansson, R.; Widhe, M.; Benselfelt, T.; Håkansson, K. M. O.; Lundell, F.; Hedhammar, M.; Söderberg, L. D. Ultrastrong and Bioactive Nanostructured Bio-Based Composites. ACS Nano 2017, 11, 5148– 5159, DOI: 10.1021/acsnano.7b0230520Ultrastrong and Bioactive Nanostructured Bio-Based CompositesMittal, Nitesh; Jansson, Ronnie; Widhe, Mona; Benselfelt, Tobias; Haakansson, Karl M. O.; Lundell, Fredrik; Hedhammar, My; Soederberg, L. DanielACS Nano (2017), 11 (5), 5148-5159CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Nature's design of functional materials relies on smart combinations of simple components to achieve desired properties. Silk and cellulose are two clever examples from nature-spider silk being tough due to high extensibility, whereas cellulose possesses unparalleled strength and stiffness among natural materials. Unfortunately, silk proteins cannot be obtained in large quantities from spiders, and recombinant prodn. processes are so far rather expensive. We have therefore combined small amts. of functionalized recombinant spider silk proteins with the most abundant structural component on Earth (cellulose nanofibrils (CNFs)) to fabricate isotropic as well as anisotropic hierarchical structures. Our approach for the fabrication of bio-based anisotropic fibers results in previously unreached but highly desirable mech. performance with a stiffness of ∼55 GPa, strength at break of ∼1015 MPa, and toughness of ∼55 MJ m-3. We also show that addn. of small amts. of silk fusion proteins to CNF results in materials with advanced biofunctionalities, which cannot be anticipated for the wood-based CNF alone. These findings suggest that bio-based materials provide abundant opportunities to design composites with high strength and functionalities and bring down our dependence on fossil-based resources.
- 21Wang, L.; Ago, M.; Borghei, M.; Ishaq, A.; Papageorgiou, A. C.; Lundahl, M.; Rojas, O. J. Conductive Carbon Microfibers Derived from Wet-Spun Lignin/Nanocellulose Hydrogels. ACS Sustainable Chem. Eng. 2019, 7, 6013– 6022, DOI: 10.1021/acssuschemeng.8b0608121Conductive Carbon Microfibers Derived from Wet-Spun Lignin/Nanocellulose HydrogelsWang, Ling; Ago, Mariko; Borghei, Maryam; Ishaq, Amal; Papageorgiou, Anastassios C.; Lundahl, Meri; Rojas, Orlando J.ACS Sustainable Chemistry & Engineering (2019), 7 (6), 6013-6022CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)We introduce an eco-friendly process to dramatically simplify carbon microfiber fabrication from biobased materials. The microfibers are first produced by wet-spinning in aq. calcium chloride soln., which provides rapid coagulation of the hydrogel precursors comprising wood-derived lignin and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCNF). The thermomech. performance of the obtained lignin/TOCNF filaments is investigated as a function of cellulose nanofibril orientation (wide angle X-ray scattering (WAXS)), morphol., SEM, and d. Following direct carbonization of the filaments at 900 °C, carbon microfibers (CMFs) are obtained with remarkably high yield, up to 41%, at lignin loadings of 70 wt % in the precursor microfibers (compared to 23% yield for those produced in the absence of lignin). Without any thermal stabilization or graphitization steps, the morphol., strength, and flexibility of the CMFs are retained to a large degree compared to those of the resp. precursors. The elec. cond. of the CMFs reach values as high as 103 S cm-1, making them suitable for microelectrodes, fiber-shaped supercapacitors, and wearable electronics. Overall, the cellulose nanofibrils act as structural elements for fast, inexpensive, and environmentally sound wet-spinning while lignin endows CMFs with high carbon yield and elec. cond.
- 22Mertaniemi, H.; Escobedo-Lucea, C.; Sanz-Garcia, A.; Gandía, C.; Mäkitie, A.; Partanen, J.; Ikkala, O.; Yliperttula, M. Human Stem Cell Decorated Nanocellulose Threads for Biomedical Applications. Biomaterials 2016, 82, 208– 220, DOI: 10.1016/j.biomaterials.2015.12.02022Human stem cell decorated nanocellulose threads for biomedical applicationsMertaniemi, Henrikki; Escobedo-Lucea, Carmen; Sanz-Garcia, Andres; Gandia, Carolina; Makitie, Antti; Partanen, Jouni; Ikkala, Olli; Yliperttula, MarjoBiomaterials (2016), 82 (), 208-220CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)Upon surgery, local inflammatory reactions and postoperative infections cause complications, morbidity, and mortality. Delivery of human adipose mesenchymal stem cells (hASC) into the wounds is an efficient and safe means to reduce inflammation and promote wound healing. However, administration of stem cells by injection often results in low cell retention, and the cells deposit in other organs, reducing the efficiency of the therapy. Thus, it is essential to improve cell delivery to the target area using carriers to which the cells have a high affinity. Moreover, the application of hASC in surgery has typically relied on animal-origin components, which may induce immune reactions or even transmit infections due to pathogens. To solve these issues, we first show that native cellulose nanofibers (nanofibrillated cellulose, NFC) extd. from plants allow prepn. of glutaraldehyde cross-linked threads (NFC-X) with high mech. strength even under the wet cell culture or surgery conditions, characteristically challenging for cellulosic materials. Secondly, using a xenogeneic free protocol for isolation and maintenance of hASC, we demonstrate that cells adhere, migrate and proliferate on the NFC-X, even without surface modifiers. Cross-linked threads were not found to induce toxicity on the cells and, importantly, hASC attached on NFC-X maintained their undifferentiated state and preserved their bioactivity. After intradermal suturing with the hASC decorated NFC-X threads in an ex vivo expt., cells remained attached to the multifilament sutures without displaying morphol. changes or reducing their metabolic activity. Finally, as NFC-X optionally allows facile surface tailoring if needed, we anticipate that stem-cell-decorated NFC-X opens a versatile generic platform as a surgical bionanomaterial for fighting postoperative inflammation and chronic wound healing problems.
- 23Peng, F.; Zhang, L.; Wang, H.; Lv, P.; Yu, H. Sulfonated Carbon Nanotubes as a Strong Protonic Acid Catalyst. Carbon 2005, 43, 2405– 2408, DOI: 10.1016/j.carbon.2005.04.00423Sulfonated carbon nanotubes as a strong protonic acid catalystPeng, Feng; Zhang, Lei; Wang, Hongjuan; Lu, Ping; Yu, HaoCarbon (2005), 43 (11), 2405-2408CODEN: CRBNAH; ISSN:0008-6223. (Elsevier Ltd.)Sulfonated carbon nanotubes with a high d. of sulfonic acid groups were prepd. by reacting concd. sulfuric acid with multiwall carbon nanotubes at 250°. The carbon nanotubes are not oxidized, but are sulfonated, although concd. H2SO4 is a strongly oxidizing agent at high temps. SEM-EDS images reveal that the morphol. and structure of the carbon nanotubes did not change after sulfonation. It is suggested that the surface of the carbon nanotubes can be functionalized by -SO3H or -SO2NH2 groups, and the latter have good thermal stability at temps ≤500 K. A novel strong protonic acid catalyst is formed with high catalytic activity in esterification with a potential to replace unrecyclable and difficult to sep. "liq. acid" catalysts.
- 24Bristow, J. A.; Kolseth, P. Paper Structure and Properties; Dekker: New York, 1986.There is no corresponding record for this reference.
- 25Wang, M.; Yu, D.-G.; Li, X.; Williams, G. R. The Development and Bio-Applications of Multifluid Electrospinning. Mater. Highlights 2020, 1, DOI: 10.2991/mathi.k.200521.001There is no corresponding record for this reference.
Supporting Information
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsanm.0c02192.
SEM image of a nonsputtered core–shell CNF–CNT filament (PDF)
Terms & Conditions
Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.