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  • 1.
    Abitbol, Tiffany
    et al.
    RISE Research Institutes of Sweden. EPFL, Switzerland.
    Kubat, Mikaela
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Brännvall, Elisabet
    RISE Research Institutes of Sweden.
    Kotov, Nikolay
    KTH Royal Institute of Technology, Sweden.
    Johnson, C Magnus
    KTH Royal Institute of Technology, Sweden.
    Nizamov, Rustem
    University of Turku, Finland.
    Nyberg, Mikael
    University of Turku, Finland.
    Miettunen, Kati
    University of Turku, Finland.
    Nordgren, Niklas
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Stevanic Srndovic, Jasna
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Guerreiro, Maria Pita
    RISE Research Institutes of Sweden.
    Isolation of Mixed Compositions of Cellulose Nanocrystals, Microcrystalline Cellulose, and Lignin Nanoparticles from Wood Pulps2023In: ACS Omega, E-ISSN 2470-1343, Vol. 8, no 24, p. 21474-21484Article in journal (Refereed)
    Abstract [en]

    From a circular economy perspective, one-pot strategies for the isolation of cellulose nanomaterials at a high yield and with multifunctional properties are attractive. Here, the effects of lignin content (bleached vs unbleached softwood kraft pulp) and sulfuric acid concentration on the properties of crystalline lignocellulose isolates and their films are explored. Hydrolysis at 58 wt % sulfuric acid resulted in both cellulose nanocrystals (CNCs) and microcrystalline cellulose at a relatively high yield (>55%), whereas hydrolysis at 64 wt % gave CNCs at a lower yield (<20%). CNCs from 58 wt % hydrolysis were more polydisperse and had a higher average aspect ratio (1.5-2×), a lower surface charge (2×), and a higher shear viscosity (100-1000×). Hydrolysis of unbleached pulp additionally yielded spherical nanoparticles (NPs) that were <50 nm in diameter and identified as lignin by nanoscale Fourier transform infrared spectroscopy and IR imaging. Chiral nematic self-organization was observed in films from CNCs isolated at 64 wt % but not from the more heterogeneous CNC qualities produced at 58 wt %. All films degraded to some extent under simulated sunlight trials, but these effects were less pronounced in lignin-NP-containing films, suggesting a protective feature, but the hemicellulose content and CNC crystallinity may be implicated as well. Finally, heterogeneous CNC compositions obtained at a high yield and with improved resource efficiency are suggested for specific nanocellulose uses, for instance, as thickeners or reinforcing fillers, representing a step toward the development of application-tailored CNC grades. © 2023 The Authors. 

  • 2.
    Andersson Ersman, Peter
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Freitag, Kathrin
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Nilsson, Marie
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Åhlin, Jessica
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Brooke, Robert
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Nordgren, Niklas
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Aulin, Christian
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Fall, Andreas
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Nevo, Yuval
    Melodea Ltd, Israel.
    Beni, Valerio
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Electrochromic Displays Screen Printed on Transparent Nanocellulose-Based Substrates2023In: Advanced Photonics Research, ISSN 2699-9293, article id 2200012Article in journal (Refereed)
    Abstract [en]

    Manufacturing of electronic devices via printing techniques is often considered to be an environmentally friendly approach, partially due to the efficient utilization of materials. Traditionally, printed electronic components (e.g., sensors, transistors, and displays) are relying on flexible substrates based on plastic materials; this is especially true in electronic display applications where, most of the times, a transparent carrier is required in order to enable presentation of the display content. However, plastic-based substrates are often ruled out in end user scenarios striving toward sustainability. Paper substrates based on ordinary cellulose fibers can potentially replace plastic substrates, but the opaqueness limits the range of applications where they can be used. Herein, electrochromic displays that are manufactured, via screen printing, directly on state-of-the-art fully transparent substrates based on nanocellulose are presented. Several different nanocellulose-based substrates, based on either nanofibrillated or nanocrystalline cellulose, are manufactured and evaluated as substrates for the manufacturing of electrochromic displays, and the optical and electrical switching performances of the resulting display devices are reported and compared. The reported devices do not require the use of metals and/or transparent conductive oxides, thereby providing a sustainable all-printed electrochromic display technology.

  • 3.
    Badal Tejedor, Maria
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Niklas, Nordgren
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation.
    Schuleit, Michael
    Novartis Pharma AG, Switzerland.
    Millqvist-Fureby, Anna
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation.
    Rutland, Mark W.
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    AFM Colloidal Probe Measurements Implicate Capillary Condensation in Punch-Particle Surface Interactions during Tableting2017In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, no 46, p. 13180-13188Article in journal (Refereed)
    Abstract [en]

    Adhesion of the powders to the punches is a common issue during tableting. This phenomenon is known as sticking and affects the quality of the manufactured tablets. Defective tablets increase the cost of the manufacturing process. Thus, the ability to predict the tableting performance of the formulation blend before the process is scaled-up is important. The adhesive propensity of the powder to the tableting tools is mostly governed by the surface-surface adhesive interactions. Atomic force microscopy (AFM) colloidal probe is a surface characterization technique that allows the measurement of the adhesive interactions between two materials of interest. In this study, AFM steel colloidal probe measurements were performed on ibuprofen, MCC (microcrystalline cellulose), α-lactose monohydrate, and spray-dried lactose particles as an approach to modeling the punch-particle surface interactions during tableting. The excipients (lactose and MCC) showed constant, small, attractive, and adhesive forces toward the steel surface after a repeated number of contacts. In comparison, ibuprofen displayed a much larger attractive and adhesive interaction increasing over time both in magnitude and in jump-in/jump-out separation distance. The type of interaction acting on the excipient-steel interface can be related to a van der Waals force, which is relatively weak and short-ranged. By contrast, the ibuprofen-steel interaction is described by a capillary force profile. Even though ibuprofen is not highly hydrophilic, the relatively smooth surfaces of the crystals allow "contact flooding" upon contact with the steel probe. Capillary forces increase because of the "harvesting" of moisture - due to the fast condensation kinetics - leaving a residual condensate that contributes to increase the interaction force after each consecutive contact. Local asperity contacts on the more hydrophilic surface of the excipients prevent the flooding of the contact zone, and there is no such adhesive effect under the same ambient conditions. The markedly different behavior detected by force measurements clearly shows the sticky and nonsticky propensity of the materials and allows a mechanistic description.

  • 4.
    Badal Tejedor, Maria
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Chemistry and Materials. KTH Royal Institute of Technology, Sweden.
    Niklas, Nordgren
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Chemistry and Materials.
    Schuleit, Michael
    Novartis Pharma AG, Switzerland.
    Pazesh, Samaneh
    Uppsala University, Sweden.
    Alderborn, Göran
    Uppsala University, Sweden.
    Millqvist-Fureby, Anna
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Chemistry and Materials.
    Rutland, Mark W.
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Chemistry and Materials. KTH Royal Institute of Technology, Sweden.
    Determination of interfacial amorphicity in functional powders2017In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, no 4, p. 920-926Article in journal (Refereed)
    Abstract [en]

    The nature of the surfaces of particles of pharmaceutical ingredients, food powders, and polymers is a determining factor for their performance in for example tableting, powder handling, or mixing. Changes on the surface structure of the material will impact the flow properties, dissolution rate, and tabletability of the powder blend. For crystalline materials, surface amorphization is a phenomenon which is known to impact performance. Since it is important to measure and control the level of amorphicity, several characterization techniques are available to determine the bulk amorphous content of a processed material. The possibility of characterizing the degree of amorphicity at the surface, for example by studying the mechanical properties of the particles' surface at the nanoscale, is currently only offered by atomic force microscopy (AFM). The AFM PeakForce QNM technique has been used to measure the variation in energy dissipation (eV) at the surface of the particles which sheds light on the mechanical changes occurring as a result of amorphization or recrystallization events. Two novel approaches for the characterization of amorphicity are presented here. First, since particles are heterogeneous, we present a methodology to present the results of extensive QNM analysis of multiple particles in a coherent and easily interpreted manner, by studying cumulative distributions of dissipation data with respect to a threshold value which can be used to distinguish the crystalline and amorphous states. To exemplify the approach, which is generally applicable to any material, reference materials of purely crystalline α-lactose monohydrate and completely amorphous spray dried lactose particles were compared to a partially amorphized α-lactose monohydrate sample. Dissipation data are compared to evaluations of the lactose samples with conventional AFM and SEM showing significant topographical differences. Finally, the recrystallization of the surface amorphous regions in response to humidity was followed by studying the dissipation response of a well-defined surface region over time, which confirms both that dissipation measurement is a useful measure of surface amorphicity and that significant recrystallization occurs at the surface in response to humidity.

  • 5.
    Badal Tejedor, Maria
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor. KTH Royal Institute of Technology, Sweden.
    Niklas, Nordgren
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Schuleit, Michael
    Novartis Pharma AG, Switzerland.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor. KTH Royal Institute of Technology, Sweden.
    Millqvist-Fureby, Anna
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Tablet mechanics depend on nano and micro scale adhesion, lubrication and structure2015In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 486, no 1-2, p. 315-323Article in journal (Refereed)
    Abstract [en]

    Tablets are the most convenient form for drug administration. However, despite the ease of manufacturing problems such as powder adhesion occur during the production process. This study presents surface and structural characterization of tablets formulated with commonly used excipients (microcrystalline cellulose (MCC), lactose, mannitol, magnesium (Mg) stearate) pressed under different compaction conditions. Tablet surface analyses were performed with scanning electron microscopy (SEM), profilometry and atomic force microscopy (AFM). The mechanical properties of the tablets were evaluated with a tablet hardness test. Local adhesion detected by AFM decreased when Mg stearate was present in the formulation. Moreover, the tablet strength of plastically deformable excipients such as MCC was significantly decreased after addition of Mg stearate. Combined these facts indicate that Mg stearate affects the particle-particle bonding and thus elastic recovery. The MCC excipient also displayed the highest hardness which is characteristic for a highly cohesive material. This is discussed in the view of the relatively high adhesion found between MCC and a hydrophilic probe at the nanoscale using AFM. In contrast, the tablet strength of brittle materials like lactose and mannitol is unaffected by Mg stearate. Thus fracture occurs within the excipient particles and not at particle boundaries, creating new surfaces not previously exposed to Mg stearate. Such uncoated surfaces may well promote adhesive interactions with tools during manufacture.

  • 6.
    Badal Tejedor, Maria
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Pazesh, Samaneh
    Uppsala University, Sweden.
    Niklas, Nordgren
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation.
    Schuleit, Micheal
    Novartis Pharma AG, Switzerland.
    Rutland, Mark W.
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Alderborn, Göran
    Uppsala University, Sweden.
    Millqvist-Fureby, Anna
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation.
    Milling induced amorphisation and recrystallization of α-lactose monohydrate2018In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 537, no 1-2, p. 140-147Article in journal (Refereed)
    Abstract [en]

    Preprocessing of pharmaceutical powders is a common procedure to condition the materials for a better manufacturing performance. However, such operations may induce undesired material properties modifications when conditioning particle size through milling, for example. Modification of both surface and bulk material structure will change the material properties, thus affecting the processability of the powder. Hence it is essential to control the material transformations that occur during milling. Topographical and mechanical changes in surface properties can be a preliminary indication of further material transformations. Therefore a surface evaluation of the α-lactose monohydrate after short and prolonged milling times has been performed. Unprocessed α-lactose monohydrate and spray dried lactose were evaluated in parallel to the milled samples as reference examples of the crystalline and amorphous lactose structure. Morphological differences between unprocessed α-lactose, 1 h and 20 h milled lactose and spray dried lactose were detected from SEM and AFM images. Additionally, AFM was used to simultaneously characterize particle surface amorphicity by measuring energy dissipation. Extensive surface amorphicity was detected after 1 h of milling while prolonged milling times showed only a moderate particle surface amorphisation. Bulk material characterization performed with DSC indicated a partial amorphicity for the 1 h milled lactose and a fully amorphous thermal profile for the 20 h milled lactose. The temperature profiles however, were shifted somewhat in the comparison to the amorphous reference, particularly after extended milling, suggesting a different amorphous state compared to the spray-dried material. Water loss during milling was measured with TGA, showing lower water content for the lactose amorphized through milling compared to spray dried amorphous lactose. The combined results suggest a surface-bulk propagation of the amorphicity during milling in combination with a different amorphous structural conformation to that of the amorphous spray dried lactose. The hardened surface may be due to either surface crystallization of lactose or to formation of a low-water glass transition.

  • 7.
    Fall, Andreas
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Zhao, Wei
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Blademo, Åsa
    RISE Research Institutes of Sweden.
    Bodelsson, Jens
    RISE Research Institutes of Sweden.
    Sugunan, Abhilash
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Nordgren, Niklas
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Abitbol, Tiffany
    RISE Research Institutes of Sweden.
    Carlmark, Anna
    RISE Research Institutes of Sweden.
    Gillgren, Thomas
    RISE Research Institutes of Sweden.
    Hybrid Materials of Nanocellulose and Graphene2019In: International Conference on Nanotechnology for Renewable Materials 2019, TAPPI Press , 2019, Vol. 2, p. 1069-1080Conference paper (Refereed)
  • 8.
    Fallqvist, Björn
    et al.
    KTH Royal Institute of Technology, Sweden.
    Fielden, Matthew L.
    KTH Royal Institute of Technology, Sweden.
    Pettersson, Torbjörn
    KTH Royal Institute of Technology, Sweden.
    Niklas, Nordgren
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Kroon, Martin
    KTH Royal Institute of Technology, Sweden.
    Gad, Annica K. B.
    Karolinska Institute, Sweden.
    Experimental and computational assessment of F-actin influence in regulating cellular stiffness and relaxation behaviour of fibroblasts2016In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 59, p. 168-184Article in journal (Refereed)
    Abstract [en]

    In biomechanics, a complete understanding of the structures and mechanisms that regulate cellular stiffness at a molecular level remain elusive. In this paper, we have elucidated the role of filamentous actin (F-actin) in regulating elastic and viscous properties of the cytoplasm and the nucleus. Specifically, we performed colloidal-probe atomic force microscopy (AFM) on BjhTERT fibroblast cells incubated with Latrunculin B (LatB), which results in depolymerisation of F-actin, or DMSO control. We found that the treatment with LatB not only reduced cellular stiffness, but also greatly increased the relaxation rate for the cytoplasm in the peripheral region and in the vicinity of the nucleus. We thus conclude that F-actin is a major determinant in not only providing elastic stiffness to the cell, but also in regulating its viscous behaviour. To further investigate the interdependence of different cytoskeletal networks and cell shape, we provided a computational model in a finite element framework. The computational model is based on a split strain energy function of separate cellular constituents, here assumed to be cytoskeletal components, for which a composite strain energy function was defined. We found a significant influence of cell geometry on the predicted mechanical response. Importantly, the relaxation behaviour of the cell can be characterised by a material model with two time constants that have previously been found to predict mechanical behaviour of actin and intermediate filament networks. By merely tuning two effective stiffness parameters, the model predicts experimental results in cells with a partly depolymerised actin cytoskeleton as well as in untreated control. This indicates that actin and intermediate filament networks are instrumental in providing elastic stiffness in response to applied forces, as well as governing the relaxation behaviour over shorter and longer time-scales, respectively.

  • 9.
    López-Guajardo, A.
    et al.
    University of Sheffield, UK.
    Zafar, A.
    University of Sheffield, UK.
    Al Hennawi, K.
    University of Sheffield, UK.
    Rossi, V.
    Veneto Institute of Oncology IOV-IRCCS, Italy.
    Alrwaili, A.
    University of Sheffield, UK.
    Medcalf, J. D.
    University of Sheffield, UK.
    Dunning, M.
    University of Sheffield, UK.
    Nordgren, Niklas
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Pettersson, T.
    KTH Royal Institute of Technology, Sweden.
    Estabrook, I. D.
    University of Sheffield, UK; Technische Universität Dresden, Germany.
    Hawkins, R. J.
    University of Sheffield, UK; African Institute for Mathematical Sciences, Ghana.
    Gad, A. K. B.
    University of Sheffield, UK; University of Madeira, Portugal; Karolinska Institute, Sweden.
    Regulation of cellular contractile force, shape and migration of fibroblasts by oncogenes and Histone deacetylase 62023In: Frontiers in Molecular Biosciences, E-ISSN 2296-889X, Vol. 10, article id 1197814Article in journal (Refereed)
    Abstract [en]

    The capacity of cells to adhere to, exert forces upon and migrate through their surrounding environment governs tissue regeneration and cancer metastasis. The role of the physical contractile forces that cells exert in this process, and the underlying molecular mechanisms are not fully understood. We, therefore, aimed to clarify if the extracellular forces that cells exert on their environment and/or the intracellular forces that deform the cell nucleus, and the link between these forces, are defective in transformed and invasive fibroblasts, and to indicate the underlying molecular mechanism of control. Confocal, Epifluorescence and Traction force microscopy, followed by computational analysis, showed an increased maximum contractile force that cells apply on their environment and a decreased intracellular force on the cell nucleus in the invasive fibroblasts, as compared to normal control cells. Loss of HDAC6 activity by tubacin-treatment and siRNA-mediated HDAC6 knockdown also reversed the reduced size and more circular shape and defective migration of the transformed and invasive cells to normal. However, only tubacin-mediated, and not siRNA knockdown reversed the increased force of the invasive cells on their surrounding environment to normal, with no effects on nuclear forces. We observed that the forces on the environment and the nucleus were weakly positively correlated, with the exception of HDAC6 siRNA-treated cells, in which the correlation was weakly negative. The transformed and invasive fibroblasts showed an increased number and smaller cell-matrix adhesions than control, and neither tubacin-treatment, nor HDAC6 knockdown reversed this phenotype to normal, but instead increased it further. This highlights the possibility that the control of contractile force requires separate functions of HDAC6, than the control of cell adhesions, spreading and shape. These data are consistent with the possibility that defective force-transduction from the extracellular environment to the nucleus contributes to metastasis, via a mechanism that depends upon HDAC6. To our knowledge, our findings present the first correlation between the cellular forces that deforms the surrounding environment and the nucleus in fibroblasts, and it expands our understanding of how cells generate contractile forces that contribute to cell invasion and metastasis. Copyright © 2023 López-Guajardo, Zafar, Al Hennawi, Rossi, Alrwaili, Medcalf, Dunning, Nordgren, Pettersson, Estabrook, Hawkins and Gad.

  • 10.
    Majee, Subimal
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Zhao, Wei
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. Uppsala University, Sweden.
    Sugunan, Abhilash
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Gillgren, .T
    BillerudKorsnäs AB, Sweden.
    Larsson, J. A.
    BillerudKorsnäs AB, Sweden.
    Brooke, Robert
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Nordgren, Niklas
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Zhang, Z. -B
    Uppsala University, Sweden.
    Zhang, S. -L
    Uppsala University, Sweden.
    Nilsson, David
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Ahniyaz, Anwar
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Highly Conductive Films by Rapid Photonic Annealing of Inkjet Printable Starch–Graphene Ink2021In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 9, no 5, article id 2101884Article in journal (Refereed)
    Abstract [en]

    A general formulation engineering method is adopted in this study to produce a highly concentrated (≈3 mg mL−1) inkjet printable starch–graphene ink in aqueous media. Photonic annealing of the starch–graphene ink is validated for rapid post-processing of printed films. The experimental results demonstrate the role of starch as dispersing agent for graphene in water and photonic pulse energy in enhancing the electrical properties of the printed graphene patterns, thus leading to an electrical conductivity of ≈2.4 × 104 S m−1. The curing mechanism is discussed based on systematic material studies. The eco-friendly and cost-efficient approach presented in this work is of technical potential for the scalable production and integration of conductive graphene inks for widespread applications in printed and flexible electronics. 

  • 11.
    Niklas, Nordgren
    et al.
    KTH Royal Institute of Technology, Sweden.
    Carlsson, Linn
    KTH Royal Institute of Technology, Sweden.
    Blomberg, Hanna
    KTH Royal Institute of Technology, Sweden.
    Carlmark, Anna
    KTH Royal Institute of Technology, Sweden.
    Malmström, Eva E.
    KTH Royal Institute of Technology, Sweden.
    Rutland, Mark
    RISE, SP – Sveriges Tekniska Forskningsinstitut. KTH Royal Institute of Technology, Sweden.
    Nanobiocomposite adhesion: Role of graft length and temperature in a hybrid biomimetic approach2013In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 14, no 4, p. 1003-1009Article in journal (Refereed)
    Abstract [en]

    Cellulose microspheres bearing poly(ε-caprolactone) grafts of different molecular weights were investigated to evaluate the effect of graft length on the interfacial properties. Surface force and friction measurements were performed using an atomic force microscope in colloidal probe mode. The maximum interaction distance and adhesion is dependent on the temperature and the time in contact via a diffusion controlled mechanism. The effects are highest for the longer grafts, and molecular weight thresholds were found to lie between 21 and 34 kDa at 25 C and between 9 and 21 kDa at 40 C. The interpenetration of the graft into a matrix leads to "hidden length" contributions to adhesion, analogous to those in natural biocomposites. The nanotribology results display Amontonian behavior, and the friction force at zero applied load is higher at the graft-graft interface than for a bare cellulose sphere interacting with the graft. These results clearly demonstrate the benefits of the grafted polymer layer on the adhesion, toughness, and resistance to shear in the design of cellulosic nanobiocomposites.

  • 12.
    Niklas, Nordgren
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Stiernstedt, Johanna
    Brumer, Harry
    Wågberg, Lars
    Gray, Derek G
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    CELL 109-Interactions of cellulose surfaces: Friction, adhesion and polysaccharide adsorption2007In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 233, p. 838-838Article in journal (Refereed)
  • 13.
    Nordqvist, Petra
    et al.
    KTH Royal Institute of Technology, Sweden.
    Niklas, Nordgren
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor. KTH Royal Institute of Technology, Sweden.
    Khabbaz, Farideh
    AkzoNobel, Sweden.
    Malmström, Eva
    KTH Royal Institute of Technology, Sweden.
    Plant proteins as wood adhesives: Bonding performance at the macro- and nanoscale2013In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 44, p. 246-252Article in journal (Refereed)
    Abstract [en]

    Soy protein isolate and wheat gluten were studied to evaluate their wood bonding performance. A multiscale approach was employed, combining tensile shear strength measurements, optical microscopy, and adhesion measurements at the nanoscale using atomic force microscopy. Tensile shear strength measurements were performed on beech wood substrates bonded with either dispersions of soy protein isolate or wheat gluten to investigate bond strength and water resistance. The results reveal a significant difference in bond strength between the plant proteins. Soy protein isolate is superior to wheat gluten, especially regarding water resistance, both under acidic and alkaline conditions. Cross sections of the wood substrates were examined by optical microscopy to study protein penetration and bond line thickness. The results indicate that a proper bond can be obtained using lower amount of soy protein isolate than wheat gluten. Atomic force microscopy in colloidal probe mode was used to investigate nanoscale adhesion between cellulose and solvent cast protein films. The results show that adhesion between the plant proteins and the wood component is important for the bonding performance. Further, it is shown that the results from atomic force microscopy and tensile shear strength measurements display the same trend demonstrating that the bonding properties translates well spanning regimes from the macro- to the nanoscale. The presented multiscale approach is shown to have great potential and may be used in the future to predict properties at different length scales in the design and formulation of new bioadhesives. 

  • 14.
    Olszewska, Anna Maria
    et al.
    Aalto University, Finland.
    Junka, Karoliina
    Aalto University, Finland.
    Niklas, Nordgren
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Laine, Janne
    Aalto University, Finland.
    Rutland, Mark
    RISE, SP – Sveriges Tekniska Forskningsinstitut. KTH Royal Institute of Technology, Sweden.
    Österberg, Monika
    Aalto University, Finland.
    Non-ionic assembly of nanofibrillated cellulose and polyethylene glycol grafted carboxymethyl cellulose and the effect of aqueous lubrication in nanocomposite formation2013In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 9, no 31, p. 7448-7457Article in journal (Refereed)
    Abstract [en]

    A facile route to significantly lower the frictional forces between cellulose nanofibrils (NFC) has been presented. The concept is based on the surface modification of NFC by adsorption of polyethylene glycol grafted carboxymethyl cellulose (CMC-g-PEG) via non-ionic interactions. The adsorption was studied using quartz crystal microbalance with dissipation (QCM-D). The changes in viscoelastic properties of the adsorbed layers, upon changes in pH were evaluated and attributed to the conformation of CMC. Surface forces and frictional properties of NFC films were examined using the AFM colloidal probe technique and were shown to be highly pH dependent. A significant difference in behaviour was observed upon the surface modification of NFC. After adsorption of CMC-g-PEG, repulsive forces were acting over a much longer distance than predicted by DLVO theory. This was ascribed to the CMC-g-PEG chain extension, the effect of which was even more pronounced at higher pH due to the deprotonation of carboxyl groups on CMC. A higher anionic charge resulted in increased water content and swelling of the layer. Additionally, the adsorption of CMC-g-PEG onto NFC films markedly increased the lubrication by the reduction of the friction coefficient by 65% and 88% at pH 4.5 and pH 7.3, respectively.

  • 15.
    Rathje, Li Sophie Zhao
    et al.
    Karolinska Institute, Sweden.
    Niklas, Nordgren
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Pettersson, Torbjörn
    KTH Royal Institute of Technology, Sweden.
    Rönnlund, Daniel
    AlbaNova University Center, Stockholm.
    Widengren, Jerker
    AlbaNova University Center, Stockholm.
    Aspenström, Pontus
    Karolinska Institute, Sweden.
    Gad, Annica K.B.
    Karolinska Institute, Sweden.
    Oncogenes induce a vimentin filament collapse mediated by HDAC6 that is linked to cell stiffness2014In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 111, no 4, p. 1515-1520Article in journal (Refereed)
    Abstract [en]

    Oncogenes deregulate fundamental cellular functions, which can lead to development of tumors, tumor-cell invasion, and metastasis. As the mechanical properties of cells govern cell motility, we hypothesized that oncogenes promote cell invasion by inducing cytoskeletal changes that increase cellular stiffness. We show that the oncogenes simian virus 40 large T antigen, c-Myc, and cyclin E induce spatial reorganization of the vimentin intermediate filament network in cells. At the cellular level, this reorganization manifests as increased width of vimentin fibers and the collapse of the vimentin network. At nanoscale resolution, the organization of vimentin fibers in these oncogene-expressing cells was more entangled, with increased width of the fibers compared with control cells. Expression of these oncogenes also resulted in upregulation of the tubulin deacetylase histone deacetylase 6 (HDAC6) and altered spatial distribution of acetylated microtubules. This oncogene expression also induced increases in cellular stiffness and promoted the invasive capacity of the cells. Importantly, HDAC6 was required and sufficient for the structural collapse of the vimentin filament network, and was required for increased cellular stiffness of the oncogene-expressing cells. Taken together, these data are consistent with the possibility that oncogenes can induce cellular stiffness via an HDAC6-induced reorganization of the vimentin intermediate filament network.

  • 16.
    Shimizu, Michiko
    et al.
    Kyoto Institute of Technology, Japan.
    Alvarez-Asencio, Ruben
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation.
    Niklas, Nordgren
    RISE - Research Institutes of Sweden (2017-2019), Bioscience and Materials, Surface, Process and Formulation.
    Uedono, Akira
    University of Tsukuba, Japan.
    Preparation and characterization of cellulose acetate membranes with TEMPO-oxidized cellulose nanofibrils containing alkyl ammonium carboxylates2020In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 27, no 3, p. 1357-1365Article in journal (Refereed)
    Abstract [en]

    Cellulose acetate (CA) membranes have been widely used for water purification owing to several advantages, e.g., biocompatibility and low fouling rate. However, they suffer from a lower water flux compared to the other polymeric membranes. Therefore, in this study, CA membranes were blended with 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (T-CNFs) containing quaternary alkyl ammonium (QA) carboxylates to improve their water flux. When increasing the alkyl chain length of the QAs, the positron lifetime and intensity of the CA membranes increased and decreased respectively, as revealed via positron annihilation lifetime spectroscopy. This indicated that the CA membranes had larger and fewer pores when using the T-CNFs containing QAs with longer alkyl chains. The pure water flux of these membranes also increased with the alkyl chain lengths of QAs although their rejection rate (Rj) decreased accordingly. However, they revealed a potentiality to be used as ultrafiltration membranes, allowing a 99% Rj for albumin. The tensile strength, strain to failure, and work of fracture of the CA membranes increased when blended with T-CNFs. Force measurements using the AFM colloidal probe technique showed that the adhesion between the membrane constituents depends on their surface chemistry. This indicated that the structural differences observed among the blended membranes may be due to the affinity between CA and T-CNF containing QAs with different alkyl chain lengths. This study demonstrates that the properties of CA membranes can be tailored by the addition of T-CNFs with different surface chemistries.

  • 17.
    Zhao, Wei
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Sugunan, Abhilash
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Gillgren, Thomas
    BillerudKorsnäs AB, Sweden.
    Larsson, Johan
    BillerudKorsnäs AB, Sweden.
    Zhang, Zhi-Bin
    Uppsala University, Sweden.
    Zhang, Shi-Li
    Uppsala University, Sweden.
    Niklas, Nordgren
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Sommertune, Jens
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Ahniyaz, Anwar
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Surfactant-Free Stabilization of Aqueous Graphene Dispersions Using Starch as a Dispersing Agent2021In: ACS Omega, E-ISSN 2470-1343, Vol. 6, no 18, p. 12050-12062Article in journal (Refereed)
    Abstract [en]

    Attention to graphene dispersions in water with the aid of natural polymers is increasing with improved awareness of sustainability. However, the function of biopolymers that can act as dispersing agents in graphene dispersions is not well understood. In particular, the use of starch to disperse pristine graphene materials deserves further investigation. Here, we report the processing conditions of aqueous graphene dispersions using unmodified starch. We have found that the graphene content of the starch-graphene dispersion is dependent on the starch fraction. The starch-graphene sheets are few-layer graphene with a lateral size of 3.2 μm. Furthermore, topographical images of these starch-graphene sheets confirm the adsorption of starch nanoparticles with a height around 5 nm on the graphene surface. The adsorbed starch nanoparticles are ascribed to extend the storage time of the starch-graphene dispersion up to 1 month compared to spontaneous aggregation in a nonstabilized graphene dispersion without starch. Moreover, the ability to retain water by starch is reduced in the presence of graphene, likely due to environmental changes in the hydroxyl groups responsible for starch-water interactions. These findings demonstrate that starch can disperse graphene with a low oxygen content in water. The aqueous starch-graphene dispersion provides tremendous opportunities for environmental-friendly packaging applications. © 2021 American Chemical Society.

  • 18.
    Álvarez-Asencio, Rubén
    et al.
    KTH Royal Institute of Technology, Sweden; IMDEA Nanoscience, Spain.
    Wallqvist, Viveca
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Kjellin, Mikael
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. KTH Royal Institute of Technology, Sweden.
    Camacho, Alejandra
    L’Oréal Research and Innovation, US.
    Niklas, Nordgren
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Luengo, Gustavo S.
    L’Oréal Research and Innovation, France.
    Nanomechanical properties of human skin and introduction of a novel hair indenter2016In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 54, p. 185-193Article in journal (Refereed)
    Abstract [en]

    The mechanical resistance of the stratum corneum, the outermost layer of skin, to deformation has been evaluated at different length scales using Atomic Force Microscopy. Nanomechanical surface mapping was first conducted using a sharp silicon tip and revealed that Young’s modulus of the stratum corneum varied over the surface with a mean value of about 0.4 GPa. Force indentation measurements showed permanent deformation of the skin surface only at high applied loads (above 4 μN). The latter effect was further demonstrated using nanomechanical imaging in which the obtained depth profiles clearly illustrate the effects of increased normal force on the elastic/plastic surface deformation. Force measurements utilizing the single hair fiber probe supported the nanoindentation results of the stratum corneum being highly elastic at the nanoscale, but revealed that the lateral scale of the deformation determines the effective elastic modulus.This result resolves the fact that the reported values in the literature vary greatly and will help to understand the biophysics of the interaction of razor cut hairs that curl back during growth and interact with the skin.

1 - 18 of 18
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