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  • 1.
    Antlauf, Mathis
    et al.
    Department of Physics, Umeå University, SE-90187 Umeå, Sweden.
    Boulanger, Nicolas
    Department of Physics, Umeå̊ University, SE-90187 Umeå, Sweden.
    Berglund, Linn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Andersson, Ove
    Department of Physics, Umeå University, SE-90187 Umeå, Sweden.
    Thermal Conductivity of Cellulose Fibers in Different Size Scales and Densities2021In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 22, no 9, p. 3800-3809Article in journal (Refereed)
    Abstract [en]

    Considering the growing use of cellulose in various applications, knowledge and understanding of its physical properties become increasingly important. Thermal conductivity is a key property, but its variation with porosity and density is unknown, and it is not known if such a variation is affected by fiber size and temperature. Here, we determine the relationships by measurements of the thermal conductivity of cellulose fibers (CFs) and cellulose nanofibers (CNFs) derived from commercial birch pulp as a function of pressure and temperature. The results show that the thermal conductivity varies relatively weakly with density (ρsample = 1340–1560 kg m–3) and that its temperature dependence is independent of density, porosity, and fiber size for temperatures in the range 80–380 K. The universal temperature and density dependencies of the thermal conductivity of a random network of CNFs are described by a third-order polynomial function (SI-units): κCNF = (0.0787 + 2.73 × 10–3·T – 7.6749 × 10–6·T2 + 8.4637 × 10–9·T3)·(ρsample0)2, where ρ0 = 1340 kg m–3 and κCF = 1.065·κCNF. Despite a relatively high degree of crystallinity, both CF and CNF samples show amorphous-like thermal conductivity, that is, it increases with increasing temperature. This appears to be due to the nano-sized elementary fibrils of cellulose, which explains that the thermal conductivity of CNFs and CFs shows identical behavior and differs by only ca. 6%. The nano-sized fibrils effectively limit the phonon mean free path to a few nanometers for heat conduction across fibers, and it is only significantly longer for highly directed heat conduction along fibers. This feature of cellulose makes it easier to apply in applications that require low thermal conductivity combined with high strength; the weak density dependence of the thermal conductivity is a particularly useful property when the material is subjected to high loads. The results for thermal conductivity also suggest that the crystalline structures of cellulose remain stable up to at least 0.7 GPa.

  • 2.
    Baş, Yağmur
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Berglund, Linn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Niittylä, Totte
    Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 87 Umeå, Sweden.
    Zattarin, Elisa
    Laboratory of Molecular Materials, Division of Biophysics and Biotechnology, Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping, Sweden.
    Aili, Daniel
    Laboratory of Molecular Materials, Division of Biophysics and Biotechnology, Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping, Sweden.
    Sotra, Zeljana
    Center for Disaster Medicine and Traumatology, Department of Biomedical and Clinical Sciences, Linköping University, SE-581 85 Linköping, Sweden.
    Rinklake, Ivana
    Center for Disaster Medicine and Traumatology, Department of Biomedical and Clinical Sciences, Linköping University, SE-581 85 Linköping, Sweden.
    Junker, Johan
    Center for Disaster Medicine and Traumatology, Department of Biomedical and Clinical Sciences, Linköping University, SE-581 85 Linköping, Sweden.
    Rakar, Jonathan
    Center for Disaster Medicine and Traumatology, Department of Biomedical and Clinical Sciences, Linköping University, SE-581 85 Linköping, Sweden.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Mechanical & Industrial Engineering (MIE), University of Toronto, Toronto, Ontario M5S 3G8, Canada.
    Preparation and Characterization of Softwood and Hardwood Nanofibril Hydrogels: Toward Wound Dressing Applications2023In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602Article in journal (Refereed)
    Abstract [en]

    Hydrogels of cellulose nanofibrils (CNFs) are promising wound dressing candidates due to their biocompatibility, high water absorption, and transparency. Herein, two different commercially available wood species, softwood and hardwood, were subjected to TEMPO-mediated oxidation to proceed with delignification and oxidation in a one-pot process, and thereafter, nanofibrils were isolated using a high-pressure microfluidizer. Furthermore, transparent nanofibril hydrogel networks were prepared by vacuum filtration. Nanofibril properties and network performance correlated with oxidation were investigated and compared with commercially available TEMPO-oxidized pulp nanofibrils and their networks. Softwood nanofibril hydrogel networks exhibited the best mechanical properties, and in vitro toxicological risk assessment showed no detrimental effect for any of the studied hydrogels on human fibroblast or keratinocyte cells. This study demonstrates a straightforward processing route for direct oxidation of different wood species to obtain nanofibril hydrogels for potential use as wound dressings, with softwood having the most potential.

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  • 3.
    Berglund, Linn
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Squinca, Paula
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Embrapa Instrumentation, Rua XV de Novembro 1452, 13561-206 São Carlos, São Paulo, Brazil.
    Baş, Yağmur
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Zattarin, Elisa
    Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, SE-581 83 Linköping, Sweden.
    Aili, Daniel
    Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, SE-581 83 Linköping, Sweden.
    Rakar, Jonathan
    Center for Disaster Medicine and Traumatology, Department of Biomedical and Clinical Sciences, Linköping University, SE-581 85 Linköping, Sweden.
    Junker, Johan
    Center for Disaster Medicine and Traumatology, Department of Biomedical and Clinical Sciences, Linköping University, SE-581 85 Linköping, Sweden.
    Starkenberg, Annika
    Center for Disaster Medicine and Traumatology, Department of Biomedical and Clinical Sciences, Linköping University, SE-581 85 Linköping, Sweden.
    Diamanti, Mattia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Sivlér, Petter
    S2Medical AB, SE-58273 Linköping, Sweden.
    Skog, Mårten
    S2Medical AB, SE-58273 Linköping, Sweden.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Mechanical & Industrial Engineering, University of Toronto, ON M5S 3G8 Toronto, Canada; Wallenberg Wood Science Center (WWSC), Luleå̊ University of Technology, SE 97187 Luleå, Sweden.
    Self-Assembly of Nanocellulose Hydrogels Mimicking Bacterial Cellulose for Wound Dressing Applications2023In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 24, no 5, p. 2264-2277Article in journal (Refereed)
    Abstract [en]

    The self-assembly of nanocellulose in the form of cellulose nanofibers (CNFs) can be accomplished via hydrogen-bonding assistance into completely bio-based hydrogels. This study aimed to use the intrinsic properties of CNFs, such as their ability to form strong networks and high absorption capacity and exploit them in the sustainable development of effective wound dressing materials. First, TEMPO-oxidized CNFs were separated directly from wood (W-CNFs) and compared with CNFs separated from wood pulp (P-CNFs). Second, two approaches were evaluated for hydrogel self-assembly from W-CNFs, where water was removed from the suspensions via evaporation through suspension casting (SC) or vacuum-assisted filtration (VF). Third, the W-CNF-VF hydrogel was compared to commercial bacterial cellulose (BC). The study demonstrates that the self-assembly via VF of nanocellulose hydrogels from wood was the most promising material as wound dressing and displayed comparable properties to that of BC and strength to that of soft tissue.

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  • 4.
    Eyholzer, Christian
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Wood Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland.
    Borges de Couraça, A.
    Laboratoire de Technologie des Composites et Polymères (LTC), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
    Duc, F.
    Laboratoire de Technologie des Composites et Polymères (LTC), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
    Bourban, P.E.
    Laboratoire de Technologie des Composites et Polymères (LTC), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
    Tingaut, P.
    Wood Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland.
    Zimmerman, T.
    Wood Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland.
    Månsson, J.A.E.
    Laboratoire de Technologie des Composites et Polymères (LTC), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Biocomposite hydrogels with carboxymethylated, nanofibrillated cellulose powder for replacement of the nucleus pulposus2011In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 12, no 5, p. 1419-1427Article in journal (Refereed)
    Abstract [en]

    Biocomposite hydrogels with carboxymethylated, nanofibrillated cellulose (c-NFC) powder were prepared by UV polymerization of N-vinyl-2-pyrrolidone with Tween 20 trimethacrylate as a crosslinking agent for replacement of the native, human nucleus pulposus (NP) in intervertebral discs. The swelling ratios and the moduli of elasticity in compression of neat and biocomposite hydrogels were evaluated in dependence of c-NFC concentration (ranging from 0 to 1.6% v/v) and degree of substitution (DS, ranging from 0 to 0.23). The viscoelastic properties in shear and the material relaxation behavior in compression were measured for neat and biocomposite hydrogels containing 0.4% v/v of fibrils (DS ranging from 0 to 0.23) and their morphologies were characterized by cryo-scanning electron microscopy (cryo-SEM). The obtained results show that the biocomposite hydrogels can successfully mimic the mechanical and swelling behavior of the NP. In addition, the presence of the c-NFC show lower strain values after cyclic compression tests and consequently create improved material relaxation properties, compared to neat hydrogels. Among the tested samples, the biocomposite hydrogel containing 0.4% v/v of c-NFC with a DS of 0.17 shows the closest behavior to native NP. Further investigation should focus on evaluation and improvement of the long-term relaxation behavior.

  • 5.
    Geng, Shiyu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Yao, Kun
    Division of Glycoscience, Department of Chemistry, KTH Royal Institute of Technology.
    Zhou, Qi
    Division of Glycoscience, Department of Chemistry, KTH Royal Institute of Technology.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Fibre and Particle Engineering, University of Oulu.
    High-strength, High-toughness Aligned Polymer-based Nanocomposite Reinforced with Ultra-low Weight Fraction of Functionalized Nanocellulose2018In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 19, no 10, p. 4075-4083Article in journal (Refereed)
    Abstract [en]

    Multifunctional lightweight, flexible, yet strong polymer-based nanocomposites are highly desired for specific applications. However, the control of orientation and dispersion of reinforcing nanoparticles and the optimization of the interfacial interaction still pose substantial challenges in nanocellulose-reinforced polymer composites. In this study, poly(ethylene glycol)-grafted nanocellulose fibers (TOCNF-g-PEG) has demonstrated much better dispersion in a poly(lactic acid) (PLA) matrix as compared to unmodified nanocellulose fibers. Through a uniaxial drawing method, aligned PLA/nanocellulose nanocomposites with high strength, high toughness, and unique optical behavior are obtained. With the incorporation of only 0.1 wt% of TOCNF-g-PEG in PLA, the ultimate strength of the nanocomposite reaches 343 MPa, which is significantly higher than that of other aligned PLA-based nanocomposites reported previously. Compared with the aligned nanocomposite reinforced with unmodified nanocellulose, the ultimate strength and toughness are enhanced by 39% and 70%, respectively. Moreover, the aligned nanocomposite film is highly transparent and possesses an anisotropic light scattering effect, revealing its significant potential for optical applications.

  • 6.
    Goetz, Lee
    et al.
    Institute of Paper Science and Technology, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta.
    Folston, Marcus
    Institute of Paper Science and Technology, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta.
    Mathew, Aji P.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ragauskas, Arthur J.
    Institute of Paper Science and Technology, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta.
    Poly(methyl vinyl ether-co-maleic acid)-Polyethylene glycol nanocomposites cross-linked in situ with cellulose nanowhiskers2010In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 11, no 10, p. 2660-2666Article in journal (Refereed)
    Abstract [en]

    Nanocomposites were developed by cross-linking cellulose nanowhiskers with poly(methyl vinyl ether-co-maleic acid) and polyethylene glycol. Nuclear magnetic resonance (NMR) studies showed cross-linking occurs between the matrix and cellulose nanowhiskers via an esterification reaction. Proton NMR T 2 relaxation experiments provided information on the mobility of the polymer chains within the matrix, which can be related to the structure of the cross-linked nanocomposite. The nanocomposite was found to consist of mobile chain portions between cross-linked junction points and immobilized chain segments near or at those junction points, whose relative fraction increased upon further incorporation of cellulose nanowhiskers. Atomic force microscopy images showed a homogeneous dispersion of nanowhiskers in the matrix even at high nanowhisker content, which can be attributed to cross-linking of the nanowhiskers in the matrix. Relative humidity conditions were found to affect the mechanical properties of the composites negatively while the nanowhiskers content had a positive effect. It is expected that the cross-links between the matrix and the cellulose nanowhiskers trap the nanowhiskers in the cross-linked network, preventing nanowhisker aggregation subsequently producing cellulose nanocomposites with unique mechanical behaviors. The results show that in situ cross-linking of cellulose nanowhiskers with a matrix polymer is a promising route to obtain nanocomposites with well dispersed nanowhiskers, tailored nanostructure, and mechanical performance

  • 7.
    Kvien, Ingvild
    et al.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Tanem, Björn Steinar
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Oksman, Kristiina
    Characterization of cellulose whiskers and their nanocomposites by atomic force and electron microscopy2005In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 6, no 6, p. 3160-3165Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to compare and explore electron microscopy and atomic force microscopy (AFM) for structure determination of cellulose whiskers and their nanocomposite with poly(lactic acid). From conventional bright-field transmission electron microscopy (TEM) it was possible to identify individual whiskers, which enabled determination of their sizes and shape. AFM overestimated the width of the whiskers due to the tip-broadening effect. Field emission scanning electron microscopy (FESEM) allowed for a quick examination giving an overview of the sample; however, the resolution was considered insufficient for detailed information. Ultramicrotomy of nanocomposite films at cryogenic temperatures enabled detailed inspection of the cellulose whiskers in the poly(lactic acid) matrix by AFM. FESEM applied on fractured surfaces allowed insight into the morphology of the nanocomposite, although rather restricted due to the metal coating and limited resolution. Detailed information was obtained from TEM; however, this technique required staining and suffered in general from limited contrast and beam sensitivity of the material

  • 8.
    Lindh, Jonas
    et al.
    Nanotechnology and Functional Materials, Department of Engineering Sciences, Box 534, Uppsala University.
    Carlsson, Daniel O.
    Nanotechnology and Functional Materials, Department of Engineering Sciences, Box 534, Uppsala University.
    Strømme, Maria
    Nanotechnology and Functional Materials, Department of Engineering Sciences, Box 534, Uppsala University.
    Mihranyan, Albert
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Convenient one-pot formation of 2,3-dialdehyde cellulose beads via periodate oxidation of cellulose in water2014In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 15, no 5, p. 1928-1932Article in journal (Refereed)
  • 9. Mathew, Aji P.
    Morphological investigation of nanocomposites from sorbitol plasticized starch and tunicin whiskers2002In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 3, no 3, p. 609-617Article in journal (Refereed)
    Abstract [en]

    Nanocomposites were prepared from waxy maize starch plasticized with sorbitol as the matrix and a stable aqueous suspension of tunicin whiskers-an animal cellulose-as the reinforcing phase. The composites were conditioned at different relative humidity levels. The conditioned films were characterized using scanning electron microscopy, differential scanning calorimetry, water uptake experiments, and wide-angle X-ray scattering studies. Contrarily to our previous report concerning tunicin whisker filled glycerol plasticized starch nanocomposites (Macromolecules 2000, 33, 8344), the present system exhibited a single glass-rubber transition, and no evidence of transcrystallization of amylopectin on cellulose whisker surfaces and resultant antiplasticizing effects were observed. It was found that the glass-rubber transition temperature of the plasticized amylopectin matrix first increases up a whiskers content around 10-15 wt % and then decreases. A significant increase in crystallinity was observed in the composites by increasing either moisture content or whiskers content

  • 10. Mathew, Aji P.
    et al.
    Dufresne, Alain
    Université Joseph Fourier.
    Plasticized waxy maize starch: effect of polyols and relative humidity on material properties2002In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 3, no 5, p. 1101-1108Article in journal (Refereed)
    Abstract [en]

    The plasticizing effect of different polyols such as glycerol, xylitol, sorbitol, and maltitol on waxy maize starch was investigated. The concentration of plasticizer was fixed at 33 wt % (dry basis of starch). The structure and mechanical performance of resulting films conditioned at different relative humidity levels were studied in detail. The effect of the plasticizer on the glass-rubber transition temperature (Tg) and crystallinity was characterized using differential scanning calorimetry. It was found that Tg decreases with increasing moisture content and decreasing molecular weight of the plasticizer. The water resistance of starch increased steadily with the molecular weight of the plasticizer and was directly proportional to the ratio of the end to total hydroxyl groups. As the molecular weight of the plasticizer increased, the brittleness of the dry system increased. However, the use of high molecular plasticizer allowed good mechanical properties of the moist material to be obtained in terms of both stiffness and elongation at break.

  • 11. Mathew, Aji P.
    et al.
    Laborie, Marie
    Washington State University.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Cross-Linked Chitosan/Chitin crystal nanocomposites with improved permeation selectivity and pH stability2009In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 10, no 6, p. 1627-1632Article in journal (Refereed)
    Abstract [en]

    This study is aimed at developing and characterizing cross-linked bionanocomposites for membrane applications using chitosan as the matrix, chitin nanocrystals as the functional phase, and gluteraldehyde as the cross-linker. The nanocomposites' chemistry and morphology were examined by estimation of gel content, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and atomic force microscopy (AFM), whereby the occurrence of cross-linking and nanoscale dispersion of chitin in the matrix was confirmed. Besides, cross-linking and chitin whiskers content were both found to impact the water uptake mechanism. Cross-linking provided dimensional stability in acidic medium and significantly decreased the equilibrium water uptake. Incorporation of chitin nanocrystals provided increased permeation selectivity to chitosan in neutral and acidic medium.

  • 12.
    Naseri, Narges
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Materials and Environmental Chemistry, Stockholm University, SE-10691 Stockholm, Sweden.
    Deepa, B.
    Department of Chemistry, Bishop Moore College, Mavelikara 690101, Kerala India.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Materials and Environmental Chemistry, Stockholm University, SE-10691 Stockholm, Sweden.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Girandon, Lenart
    Educell ltd., Prevale 9, 1236 Trzin, Slovenia.
    Nanocellulose-Based Interpenetrating Polymer Network (IPN) Hydrogels for Cartilage Applications2016In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 17, no 11, p. 3714-3723Article in journal (Refereed)
    Abstract [en]

    Double cross-linked interpenetrating polymer network (IPN) hydrogels of sodium alginate and gelatin (SA/G) reinforced with 50 wt % cellulose nanocrystals (CNC) have been prepared via the freeze-drying process. The IPNs were designed to incorporate CNC with carboxyl surface groups as a part of the network contribute to the structural integrity and mechanical stability of the hydrogel. Structural morphology studies of the hydrogels showed a three-dimensional (3D) network of interconnected pores with diameters in the range of 10-192 μm and hierarchical pores with a nanostructured pore wall roughness, which has potential benefits for cell adhesion. Significant improvements in the tensile strength and strain were achieved in 98% RH at 37 °C for CNC cross-linked IPNs. The high porosity of the scaffolds (>93%), high phosphate buffered saline (PBS) uptake, and cytocompatibility toward mesenchymal stem cells (MSCs) are confirmed and considered beneficial for use as a substitute for cartilage.

  • 13.
    Squinca, Paula
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Embrapa Instrumentation, Rua XV de Novembro 1452, 13561-206 São Carlos, SP, Brazil; Graduate Program of Chemical Engineering, Federal University of São Carlos, Rod. Washington Luís-km 235, 13565-905 São Carlos, SP, Brazil.
    Berglund, Linn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hanna, Kristina
    Center for Disaster Medicine and Traumatology, Department of Biomedical and Clinical Sciences, Linköping University, SE-581 85 Linköping, Sweden.
    Rakar, Jonathan
    Center for Disaster Medicine and Traumatology, Department of Biomedical and Clinical Sciences, Linköping University, SE-581 85 Linköping, Sweden.
    Junker, Johan
    Center for Disaster Medicine and Traumatology, Department of Biomedical and Clinical Sciences, Linköping University, SE-581 85 Linköping, Sweden.
    Khalaf, Hazem
    Cardiovascular Research Centre, School of Medical Sciences, Örebro University, SE-703 62 Örebro, Sweden.
    Farinas, Cristiane S.
    Embrapa Instrumentation, Rua XV de Novembro 1452, 13561-206 São Carlos, SP, Brazil; Graduate Program of Chemical Engineering, Federal University of São Carlos, Rod. Washington Luís-km 235, 13565-905 São Carlos, SP, Brazil.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Mechanical & Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario M5S 3G8, Canada.
    Multifunctional Ginger Nanofiber Hydrogels with Tunable Absorption: The Potential for Advanced Wound Dressing Applications2021In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 22, no 8, p. 3202-3215Article in journal (Refereed)
    Abstract [en]

    In this study, ginger residue from juice production was evaluated as a raw material resource for preparation of nanofiber hydrogels with multifunctional properties for advanced wound dressing applications. Alkali treatment was applied to adjust the chemical composition of ginger fibers followed by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation prior to nanofiber isolation. The effect of alkali treatment on hydrogel properties assembled through vacuum filtration without addition of any chemical cross-linker was evaluated. An outstanding absorption ability of 6200% combined with excellent mechanical properties, tensile strength of 2.1 ± 0.2 MPa, elastic modulus of 15.3 ± 0.3 MPa, and elongation at break of 25.1%, was achieved without alkali treatment. Furthermore, the absorption capacity was tunable by applying alkali treatment at different concentrations and by adjusting the hydrogel grammage. Cytocompatibility evaluation of the hydrogels showed no significant effect on human fibroblast proliferation in vitro. Ginger essential oil was used to functionalize the hydrogels by providing antimicrobial activity, furthering their potential as a multifunctional wound dressing. 

  • 14.
    Tanpichai, Supachok
    et al.
    Materials Science Centre, School of Materials, University of Manchester.
    Quero, Franck
    Materials Science Centre, School of Materials, University of Manchester.
    Nogi, Masaya
    cInstitute of Scientific and Industrial Research, Osaka University.
    Yano, Hiroyuki
    Research Institute for the Sustainable Humanosphere, Kyoto University.
    Young, Robert J.
    Materials Science Centre, School of Materials, University of Manchester.
    Lindström, Tom
    Innventia AB.
    Sampson, William W.
    Materials Science Centre, School of Materials, University of Manchester.
    Eichhorn, Stephen J.
    Materials Science Centre, School of Materials, University of Manchester.
    Effective young's modulus of bacterial and microfibrillated cellulose fibrils in fibrous networks2012In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 13, no 5, p. 1340-1349Article in journal (Refereed)
    Abstract [en]

    The deformation micromechanics of bacterial cellulose (BC) and microfibrillated cellulose (MFC) networks have been investigated using Raman spectroscopy. The Raman spectra of both BC and MFC networks exhibit a band initially located at ∼1095 cm-1. We have used the intensity of this band as a function of rotation angle of the specimens to study the cellulose fibril orientation in BC and MFC networks. We have also used the change in this peak's wavenumber position with applied tensile deformation to probe the stress-transfer behavior of these cellulosic materials. The intensity of this Raman band did not change significantly with rotation angle, indicating an in-plane 2D network of fibrils with uniform random orientation; conversely, a highly oriented flax fiber exhibited a marked change in intensity with rotation angle. Experimental data and theoretical analysis shows that the Raman band shift rate arising from deformation of networks under tension is dependent on the angles between the axis of fibrils, the strain axis, the incident laser polarization direction, and the back scattered polarization configurations. From this analysis, the effective moduli of single fibrils of BC and MFC in the networks were estimated to be in the ranges of 79-88 and 29-36 GPa, respectively. It is shown also that for the model to fit the data it is necessary to use a negative Poisson's ratio for MFC networks and BC networks. Discussion of this in-plane "auxetic" behavior is given.

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