| 1. |
- Acciaro, Roberta, et al.
(author)
-
Investigation of the formation, structure and release characteristics of self-assembled composite films of cellulose nanofibrils and temperature responsive microgels
- 2011
-
In: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 7:4, s. 1369-1377
-
Journal article (peer-reviewed)abstract
- The possibility of forming self-organized films using charge-stabilized dispersions of cellulose I nanofibrils and microgel beads of poly-(N-isopropylacrylamide-co-acrylic acid) copolymer is presented. The build-up behavior and the properties of the layer-by-layer (LbL)-constructed films were studied using quartz crystal microbalance with dissipation (QCM-D) and ellipsometry. The morphology of the formed films was also characterized using atomic force microscopy (AFM) imaging. The applied methods clearly demonstrated the successful LbL-assembly of the monodisperse microgels and nanofibrils. The in situ QCM-D measurements also revealed that contrary to the polyelectrolyte bound microgel particles, the nanofibrils-bound gel beads preserve their highly swollen state and do not suffer a partial collapse due to the lack of interdigitation of the oppositely charged components. To probe the accessibility of the gel beads in the formed films, the room temperature (similar to 25 degrees C) loading and release of a fluorescent dye (FITC) was also investigated. The incorporation of the cellulose nanofibrils into the multilayer resulted in an open structure that was found easily penetrable for the dye molecules even at constant room temperature, which is in sharp contrast with previously reported systems based on synthetic polyelectrolytes. The amount of dye released from the multilayer films could be fine-tuned with the number of bilayers. Finally, the thermoresponsivity of the films was also shown by triggering the burst release of the loaded dye when the film was collapsed.
|
|
| 2. |
- Andersson Ersman, Peter, et al.
(author)
-
Electrochromic Displays Screen Printed on Transparent Nanocellulose-Based Substrates
- 2023
-
In: Advanced Photonics Research. - : John Wiley & Sons, Ltd. - 2699-9293.
-
Journal article (peer-reviewed)abstract
- 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. |
|
|
| 4. |
|
|
| 5. |
- Aulin, Christian, et al.
(author)
-
Aerogels from nanofibrillated cellulose with tunable oleophobicity
- 2010
-
In: SOFT MATTER. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 6:14, s. 3298-3305
-
Journal article (peer-reviewed)abstract
- The formation of structured porous aerogels of nanofibrillated cellulose (NFC) by freeze-drying has been demonstrated. The aerogels have a high porosity, as shown by FE-SEM and nitrogen adsorption/desorption measurements, and a very low density ( < 0.03 g cm(-3)). The density and surface texture of the aerogels can be tuned by selecting the concentration of the NFC dispersions before freeze-drying. Chemical vapor deposition (CVD) of 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane (PFOTS) was used to uniformly coat the aerogel to tune their wetting properties towards non-polar liquids. An XPS analysis of the chemical composition of the PFOTS-modified aerogels demonstrated the reproducibility of the PFOTS-coating and the high atomic fluorine concentration (ca. 51%) in the surfaces. The modified aerogels formed a robust composite interface with high apparent contact angles (theta* >> 90 degrees) for castor oil (gamma(1v) = 35.8 mN m(-1)) and hexadecane (gamma(1v) = 27.5 mN m(-1)).
|
|
| 6. |
- Aulin, Christian, et al.
(author)
-
Biopolymer Coatings for Paper and Paperboard
- 2011
-
In: Biopolymers. - Chichester : John Wiley & Sons. - 9780470683415 - 9781119994312 ; , s. 255-276
-
Book chapter (other academic/artistic)
|
|
| 7. |
- Aulin, Christian, 1980-, et al.
(author)
-
Buildup of polyelectrolyte multilayers of polyethyleneimine and microfibrillated cellulose studied by in situ dual-polarization interferometry and quartz crystal microbalance with dissipation
- 2008
-
In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 24:6, s. 2509-2518
-
Journal article (peer-reviewed)abstract
- Polyethyleneimine (PEI) and Microfibrillated cellulose (MFC) have been used to buildup polyelectrolyte multilayers (PEM) on silicone oxide and silicone oxynitride surfaces at different pH values and with different electrolyte and polyelectrolyte/colloid concentrations of the components. Consecutive adsorption on these surfaces was studied by in situ dual-polarization interferometry (DPI) and quartz crystal microbalance measurements. The adsorption data obtained from both the techniques showed a steady buildup of multilayers. High pH and electrolyte concentration of the PEI solution was found to be beneficial for achieving a high adsorbed amount of PEI, and hence of MFC, during the buildup of the multilayer. On the other hand, an increase in the electrolyte concentration of the MFC dispersion was found to inhibit the adsorption of MFC onto PEL The adsorbed amount of MFC was independent of the bulk MFC concentration in the investigated concentration range (15-250 mg/L). Atomic force microscopy measurements were used to image a MFC-treated silicone oxynitride chip from DPI measurements. The surface was found to be almost fully covered by randomly oriented microfibrils after the adsorption of only one bilayer of PEI/MFC. The surface roughness expressed as the rms-roughness over 1 ÎŒm2 was calculated to be 4.6 nm (1 bilayer). The adsorbed amount of PEI and MFC and the amount of water entrapped by the individual layers in the multilayer structures were estimated by combining results from the two analytical techniques using the de Feijter formula. These results indicate a total water content of ca. 41% in the PEM.
|
|
| 8. |
|
|
| 9. |
- Aulin, Christian, et al.
(author)
-
Design of highly oleophobic cellulose surfaces from structured silicon templates
- 2009
-
In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 1:11, s. 2443-2452
-
Journal article (peer-reviewed)abstract
- Structured silicon surfaces, possessing hierarchical porous characteristics consisting of micrometer-sized cavities superimposed upon a network of nanometer-sized pillars or wires, have been fabricated by a plasma-etching process. These surfaces have superoleophobic properties, after being coated with fluorinated organic trichlorosilanes, on intrinsically oleophilic surfaces. By comparison with flat silicon surfaces, which are oleophilic, it has been demonstrated that a combination of low surface energy and the structured features of the plasma-etched surface is essential to prevent oil from penetrating the surface cavities and thus induce the observed macroscopic superoleophobic phenomena with very low contact-angle hysteresis and low roll-off angles. The structured silicon surfaces were coated with cellulose nanocrystals using the polyelectrolyte multilayer technique. The cellulose surfaces prepared in this way were then coated with a monolayer of fluorinated trichlorosilanes. These porous cellulose films displayed highly nonwetting properties against a number of liquids with low surface tension, including alkanes such as hexadecane and decane. The wettability and chemical composition of the cellulose/silicon surfaces were characterized with contact-angle goniometry and X-ray photoelectron spectroscopy, respectively. The nano/microtexture features of the cellulose/silicon surfaces were also studied with field-emission scanning electron microscopy. The highly oleophobic structured cellulose surfaces are very interesting model surfaces for the development of biomimetic self-cleaning surfaces in a vast array of products, including green constructions, packaging materials, protection against environmental fouling, sports, and outdoor clothing, and microfluidic systems.
|
|
| 10. |
|
|
| 11. |
- Aulin, Christian, et al.
(author)
-
Enhanced mechanical and gas barrier performance of plasticized cellulose nanofibril films
- 2022
-
In: Nordic Pulp & Paper Research Journal. - : De Gruyter Open Ltd. - 0283-2631 .- 2000-0669. ; 37:1, s. 138-148
-
Journal article (peer-reviewed)abstract
- Cellulose nanofibrils (CNF) are mixed with plasticizers; sorbitol and glycerol, through high-pressure homogenization to prepare multifunctional biohybrid films. The resulting plasticized films obtained after solvent evaporation are strong, flexible and demonstrate superior toughness and optical transparency. The oxygen barrier properties of the biohybrid films outperform commercial packaging materials. The sorbitol-plasticized CNF films possess excellent oxygen barrier properties, 0.34 cm3·μm/m2·day·kPa at 50 % relative humidity, while significantly enhancing the toughness and fracture strength of the films. CNF films plasticized by 20 wt.% of sorbitol and glycerol could before rupture, be strained to about 9 % and 12 %, respectively. The toughness of the plasticized films increased by ca. 300 % compared to the pristine CNF film. Furthermore, the water vapor barrier properties of the biohybrid films were also preserved by the addition of sorbitol. CNF films plasticized with sorbitol was demonstrated to simultaneously enhance fracture toughness, work of fracture, softening behavior while preserving gas barrier properties. Highly favorable thermomechanical characteristics were found with CNF/sorbitol combinations and motivate further work on this material system, for instance as a thermoformable matrix in biocomposite materials. The unique combination of excellent oxygen barrier behavior, formability and optical transparency suggest the potential of these CNF-based films as an alternative in flexible packaging of oxygen sensitive devices like thin-film transistors or organic light-emitting diode displays, gas storage applications and as barrier coatings/laminations in packaging applications, including free-standing films as aluminium-replacement in liquid board and primary packaging, as replacement for polyethylene (PE) in wrapping paper, e. g. sweats and confectionary.
|
|
| 12. |
- Aulin, Christian, et al.
(author)
-
High strength flexible and transparent nanofibrillated cellulose-nanoclay biohybrid films with tunable oxygen and water vapor permeability
- 2012
-
In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 4:20, s. 6622-6628
-
Journal article (peer-reviewed)abstract
- A novel, technically and economically benign procedure to combine vermiculite nanoplatelets with nanocellulose fibre dispersions into functional biohybrid films is presented. Nanocellulose fibres of 20 nm diameters and several micrometers in length are mixed with high aspect ratio exfoliated vermiculite nanoplatelets through high-pressure homogenization. The resulting hybrid films obtained after solvent evaporation are stiff (tensile modulus of 17.3 GPa), strong (strength up to 257 MPa), and transparent. Scanning electron microscopy (SEM) shows that the hybrid films consist of stratified nacre-like layers with a homogenous distribution of nanoplatelets within the nanocellulose matrix. The oxygen barrier properties of the biohybrid films outperform commercial packaging materials and pure nanocellulose films showing an oxygen permeability of 0.07 cm3 μm m-2 d-1 kPa -1 at 50% relative humidity. The oxygen permeability of the hybrid films can be tuned by adjusting the composition of the films. Furthermore, the water vapor barrier properties of the biohybrid films were also significantly improved by the addition of nanoclay. The unique combination of excellent oxygen barrier behavior and optical transparency suggests the potential of these biohybrid materials as an alternative in flexible packaging of oxygen sensitive devices such as thin-film transistors or organic light-emitting diode displays, gas storage applications and as barrier coatings/laminations in large volume packaging applications.
|
|
| 13. |
- Aulin, Christian, et al.
(author)
-
Multilayered Alkyd Resin/Nanocellulose Coatings for Use in Renewable Packaging Solutions with a High Level of Moisture Resistance
- 2013
-
In: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 52:7, s. 2582-2589
-
Journal article (peer-reviewed)abstract
- A surprisingly simple and rapid methodology for large-area, lightweight, and thin laminate coatings with remarkable moisture barrier properties is introduced. Commercially available paperboards are coated with thin layers of nanocellulose. The nanocellulose coating induces a surface smoothening effect on the coated sheets as characterized by environmental scanning electron microscopy and white light interferometry. A moisture-protective layer of renewable alkyd resins is deposited on the nanocellulose precoated sheets using a water-borne dispersion coating process or lithographic printing. Through an auto-oxidation process, the applied alkyd resins are transformed into moisture sealant layers. The moisture barrier properties are characterized in detail by water vapor permeability measurements at different levels of relative humidity. The water vapor barrier properties of the nanocellulose precoated substrates were significantly improved by thin layers of renewable alkyd resins. The effect of the alkyd resin properties, coating technologies, and base paper substrates on the final barrier performance of the sheets were studied. It was found that the nanocellulose coating had a notable effect on the homogeneity and barrier performance of the alkyd resin layers and in particular those alkyd resin layers that were applied by printing. The concept is environmentally friendly, energy-efficient, and economic and is ready for scaling-up via continuous roll-to-roll processes. Large-scale renewable coatings applicable for sustainable packaging solutions are foreseen.
|
|
| 14. |
|
|
| 15. |
- Aulin, Christian, et al.
(author)
-
Nanoscale Cellulose Films with Different Crystallinities and Mesostructures : Their Surface Properties and Interaction with Water
- 2009
-
In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 25:13, s. 7675-7685
-
Journal article (peer-reviewed)abstract
- A systematic study of the degree of molecular ordering and swelling of different nanocellulose model films has been conducted. Crystalline cellulose II surfaces were prepared by spin-coating of the precursor cellulose solutions onto oxidized silicon wafers before regeneration in water or by using the Langmuir-Schaefer (LS) technique. Amorphous cellulose films were also prepared by spin-coating of a precursor cellulose solution onto oxidized silicon wafers. Crystalline cellulose I surfaces were prepared by spin-coating wafers with aqueous suspensions of sulfate-stabilized cellulose nanocrystals and low-charged microfibrillated cellulose (LC-MFC). In addition, a dispersion of high-charged MFC was used for the buildup of polyelectrolyte multilayers with polyetheyleneimine on silica with the aid of the layer-by-layer (LbL) technique. These preparation methods produced smooth thin films on the nanometer scale Suitable for X-ray diffraction and swelling measurements. The surface morphology and thickness of the cellulose films were characterized in detail by atomic force microscopy (AFM) and ellipsometry measurements, respectively. To determine the surface energy of the cellulose surfaces, that Is, their ability to engage in different interactions with different materials, they were characterized through contact angle measurements against water, glycerol, and methylene iodide. Small incidence angle X-ray diffraction revealed that the nanocrystal and MFC films exhibited a cellulose I crystal structure and that the films prepared from N-methylmorpholine-N-oxide (NMMO), LiCl/DMAc solutions, using the LS technique, possessed a cellulose II structure. The degree of crystalline ordering was highest in the nanocrystal films (similar to 87%), whereas the MFC, NMMO, and LS films exhibited a degree of crystallinity of about 60%. The N,N-dimethylacetamide(DMAc)/LiCl film possessed very low crystalline ordering (<15%). It was also established that the films ha different mesostructures, that is, structures around 10 nm, depending on the preparation conditions. The LS and LiCl/DMAc films are smooth without any clear mesostructure, whereas the other films have a clear mesostructure in which the dimensions are dependent oil the size of the nanocrystals, fibrillar cellulose, and electrostatic charge of the MFC. The swelling of the films was studied using a quartz crystal microbalance with dissipation. To understand the swelling properties of the films, it was necessary to consider both the difference in crystalline ordering and the difference in mesostructure of the films.
|
|
| 16. |
- Aulin, Christian, 1980-
(author)
-
Novel oil resistant cellulosic materials
- 2009
-
Doctoral thesis (other academic/artistic)abstract
- The aim of this study has been to prepare and characterise oil resistant cellulosic materials, ranging from model surfaces to papers and aerogels. The cellulosic materials were made oil resistant by chemical and topographic modifications, based on surface energy, surface roughness and barrier approaches. Detailed wetting studies of the prepared cellulosic materials were made using contact angle measurements and standardised penetration tests with different alkanes and oil mixtures. A significant part of the activities were devoted to the development of model cellulosic surfaces with different degrees of crystalline ordering for the wetting studies. Crystalline cellulose I, II and amorphous cellulose surfaces were prepared by spin-coating of cellulose nanocrystal or microfibrillated cellulose (MFC) dispersions, with Langmuir-Schaefer (LS) films or by a layer-by-layer (LbL) deposition technique. The formation of multilayers consisting of polyethyleneimine (PEI)/anionic MFC or cationic MFC/anionic MFC was further studied and optimized in terms of total layer thickness and adsorbed amount by combining Dual Polarization Interferometry (DPI) or Stagnation Point Adsorption Reflectrometry (SPAR) with a Quartz Crystal Microbalance with Dissipation (QCM-D). The smooth cellulosic surfaces prepared had different molecular and mesostructure properties and different surface energies as shown by X-ray diffraction, Atomic Force Microscopy (AFM) imaging, ellipsometry measurements and contact angle measurements. The cellulose model surfaces were found to be ideal for detailed wetting studies, and after the surface has been coated or covalently modified with various amounts of fluorosurfactants, the fluorinated cellulose films were used to follow the spreading mechanisms of different oil mixtures. The viscosity and surface tension of the oil mixtures, as well as the dispersive surface energy of the cellulose surfaces, were found to be essential parameters governing the spreading kinetics. A strong correlation was found between the surface concentration of fluorine, the dispersive surface energy and the measured contact angle of the oil mixtures. Silicon surfaces possessing structural porous characteristics were fabricated by a plasma etching process. The structured silicon surfaces were coated with sulfate-stabilized cellulose I nanocrystals using the LbL technique. These artificial intrinsically oleophilic cellulose surfaces were made highly oleophobic when coated with a thin layer of fluorinated silanes. By comparison with flat cellulose surfaces, which are oleophilic, it is demonstrated that the surface energy and the surface texture are essential factors preventing oil from spreading on the surface and, thus, inducing the observed macroscopic oleophobic properties. The use of the MFC for surface coating on base papers demonstrated very promising characteristics as packaging materials. Environmental-Scanning Electron Microscopy (E-SEM) micrographs indicated that the MFC layer reduced the sheet porosity, i.e. the dense structure formed by the nanofibers resulted in superior oil barrier properties. Attempts were made to link the procedure for preparation of the MFC dispersions to the resulting microstructure of the coatings, and film porosity and the film moisture content to the resulting permeability properties. Finally, MFC aerogels were successfully prepared by freeze-drying. The surface texture of the porous aerogels was carefully controlled by adjusting the concentration of the MFC dispersion used for the freeze-drying. The different scales of roughness of the MFC aerogels were utilised, together with the very low surface energy created by fluorination of the aerogel, to induce highly oleophobic properties.
|
|
| 17. |
- Aulin, Christian, et al.
(author)
-
Oxygen and oil barrier properties of microfibrillated cellulose films and coatings
- 2010
-
In: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 17:3, s. 559-574
-
Journal article (peer-reviewed)abstract
- The preparation of carboxymethylated microfibrillated cellulose (MFC) films by dispersion-casting from aqueous dispersions and by surface coating on base papers is described. The oxygen permeability of MFC films were studied at different relative humidity (RH). At low RH (0%), the MFC films showed very low oxygen permeability as compared with films prepared from plasticized starch, whey protein and arabinoxylan and values in the same range as that of conventional synthetic films, e.g., ethylene vinyl alcohol. At higher RH's, the oxygen permeability increased exponentially, presumably due to the plasticizing and swelling of the carboxymethylated nanofibers by water molecules. The effect of moisture on the barrier and mechanical properties of the films was further studied using water vapor sorption isotherms and by humidity scans in dynamic mechanical analysis. The influences of the degree of nanofibrillation/dispersion on the microstructure and optical properties of the films were evaluated by field-emission scanning electron microscopy (FE-SEM) and light transmittance measurements, respectively. FE-SEM micrographs showed that the MFC films consisted of randomly assembled nanofibers with a thickness of 5-10 nm, although some larger aggregates were also formed. The use of MFC as surface coating on various base papers considerably reduced the air permeability. Environmental scanning electron microscopy (E-SEM) micrographs indicated that the MFC layer reduced sheet porosity, i.e., the dense structure formed by the nanofibers resulted in superior oil barrier properties.
|
|
| 18. |
- Aulin, Christian
(author)
-
Preparation, characterisation and wetting of fluorinated cellulose surfaces
- 2007
-
Licentiate thesis (other academic/artistic)abstract
- This thesis deals with the wetting by oil mixtures of two different model cellulose surfaces. The surfaces studied were a regenerated cellulose (RG) surface prepared by spin-coating, and a film consisting of polyelectrolyte multilayers (PEM) of Poly(ethyleneimine) (PEI) and a carboxymethylated Microfibrillated Cellulose (MFC). After coating or covalently modifying the cellulose surfaces with various amounts of fluorosurfactants, the fluorinated cellulose films were used to follow the spreading mechanisms of the different oil mixtures. The viscosity and surface tension of the oil, as well as the dispersive surface energy of the cellulose surface, are essential parameters governing the spreading kinetics. X-ray Photoelectron Spectroscopy (XPS) and dispersive surface energy measurements were made on the cellulose films treated with fluorosurfactants. A strong correlation between the surface coverage of fluorine, the dispersive surface energy and the measured contact angle of the oil mixtures was found. For example, a dispersive surface energy less than 18 mN/m was required in order for the cellulose surface to be non-wetting (θe > 90º) by castor oil. Significant parts of this work were devoted to the development of cellulose surfaces for the wetting studies. The formation of a PEM consisting of PEI and MFC was studied and the total layer thickness and adsorbed amount were optimized by combining Dual Polarization Interferometry (DPI) with a Quartz Crystal Microbalance with Dissipation (QCM-D). The adsorption behaviour as well as the influence of the charge density, pH and electrolyte concentration of PEI, and electrolyte concentration of the MFC dispersion on the adsorbed amount of MFC were investigated. Results indicate that a combination of a high pH, a fairly high electrolyte concentration for PEI solution together with low or zero electrolyte concentration for the MFC resulted in the largest possible adsorbed amounts of the individual PEI and MFC layers. The structures of the two cellulose surfaces were characterised with atomic force microscopy measurements and a difference in terms of surface structure and roughness were observed. Both surfaces were however very smooth with calculated RMS roughness values in the range of a few nanometers. The adsorption behaviour of water-dispersible fluorosurfactants physically adsorbed at various concentrations onto the two model cellulose surfaces was investigated using DPI. The aggregate structure of an anionic fluorosurfactant, perfluorooctadecanoic acid, dispersed in water was studied by Cryo Transmission Electron Microscopy (Cryo-TEM). The fluorosurfactants had an adsorption and desorption behaviour in water which was dependent on the fluorinated chain length and the aggregation form of the fluorosurfactant. Perfluorooctanoic acid and a commercial cationic fluorosurfactant with a formal composition of CF3 (CF2)nSO2NH(CH2)3-4N(CH3)3+I- was found to desorb from the MFC and RG surfaces upon rinsing with water, whereas perfluorooctadecanoic acid was strongly adsorbed to the surfaces. It is essential for a fluorosurfacatant to be strongly adsorbed to the cellulose surface even after rinsing to yield hydrophobic and lipophobic (oleophobic) properties with a large contact angle for oils and water.
|
|
| 19. |
- Aulin, Christian, et al.
(author)
-
Self-Organized Films from Cellulose I Nanofibrils Using the Layer-by-Layer Technique
- 2010
-
In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 11:4, s. 872-882
-
Journal article (peer-reviewed)abstract
- The possibility of forming self-organized films using only charge-stabilized dispersions of cellulose I nanofibrils with opposite charges is presented, that is, the multilayers were composed solely of anionically and cationically modified microfibrillated cellulose (MFC) with a low degree of substitution. The build-up behavior and the properties of the layer-by-layer (LbL)-constructed films were studied using a quartz crystal microbalance with dissipation (QCM-D) and stagnation point adsorption reflectometry (SPAR). The adsorption behavior of cationic/anionic MFC was compared with that of polyethyleneimine (PEI)/anionic MFC. The water contents of five bilayers of cationic/anionic MFC and PEI/anionic MFC were approximately 70 and 50%, respectively. The MFC surface coverage was studied by atomic force microscopy (AFM) measurements, which clearly showed a more dense fibrillar structure in the five bilayer PEI/anionic MFC than in the five bilayer cationic/anionic MFC. The forces between the cellulose-based multilayers were examined using the AFM colloidal probe technique. The forces on approach were characterized by a combination of electrostatic and steric repulsion. The wet adhesive forces were very long-range and were characterized by multiple adhesive events. Surfaces covered by PEU/anionic MFC multilayers required more energy to be separated than surfaces covered by cationic/anionic MFC multilayers.
|
|
| 20. |
- Aulin, Christian, et al.
(author)
-
Structure and Properties of Layer-by-Layer Films from Combinations of Cellulose Nanofibers, Polyelectrolytes and Colloids
- 2014
-
In: HANDBOOK OF GREEN MATERIALS, VOL 3. - : World Scientific. - 9789814566506 - 9789814566452 ; , s. 57-77
-
Book chapter (peer-reviewed)abstract
- The formation of nanometer-thin films of cellulose nanofibers (CNFs), polyelectrolytes, and/or nanoparticles has opened up new possibilities of manufacturing interactive devices with controlled mechanical properties. By controlling the charge of the CNF and the charge and 3D structure of the polyelectrolytes, it is possible to control the buildup, i.e., the thickness, the adsorbed amount, and the immobilized water of layer-by-layer (LbL) films of these materials. The charge balance between the components is not the only factor controlling the LbL formation. The structure of these adsorbed layers in combination with the properties of the constituent components will in turn control how these layers interact with, for example moist air. The mechanical properties of the LbLs can be tuned by combining the high-modulus CNF with different components. This has been shown by using a microbuckling technique where the mechanical properties of ultra-thin films can be measured. In combination with, for example, moisture-sensitive poly(ethylene imine) (PEI), the Young's modulus of CNF/PEI films can be changed by one order of magnitude when the humidity is increased from 0% RH to 50% RH. The incorporation of high-modulus nanoparticles such as SiO2 particles can also be used to prepare LbLs with a higher modulus. Examples are also given where it is shown that the color of an LbL film can be used as a non-contact moisture sensor since the thickness is related to the amount of adsorbed moisture. By chemical modification of the CNF, it is also possible to tailor the interaction between the CNF and multivalent metal ions, enabling a specific interaction between multivalent for example metal surfaces in water and modified CNF.
|
|
| 21. |
- Aulin, Christian, et al.
(author)
-
Transparent Nanocellulosic Multilayer Thin Films on Polylactic Acid with Tunable Gas Barrier Properties
- 2013
-
In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 5:15, s. 7352-7359
-
Journal article (peer-reviewed)abstract
- The layer-by-layer (LbL) deposition method was used for the build-up of alternating layers of nanofibrillated cellulose (NFC) or carboxymethyl cellulose (CMC) with a branched, cationic polyelectrolyte, polyethyleneimine (PEI) on flexible poly (lactic acid) (PLA) substrates. With this procedure, optically transparent nanocellulosic films with tunable gas barrier properties were formed. 50 layer pairs of PEI/NFC and PEI/CMC deposited on PLA have oxygen permeabilities of 0.34 and 0.71 cm(3).mu m/m(2).day.kPa at 23 degrees C and 50% relative humidity, respectively, which is in the same range as polyvinyl alcohol and ethylene vinyl alcohol. The oxygen permeability of these multilayer nanocomposites outperforms those of pure NFC films prepared by solvent-casting. The nanocellulosic LbL assemblies on PLA substrates was in detailed characterized using a quartz crystal microbalance with dissipation (QCM-D). Atomic force microscopy (AFM) reveals large structural differences between the PEI/NFC and the PEI/CMC assemblies, with the PEI/NFC assembly showing a highly entangled network of nanofibrils, whereas the PEI/CMC surfaces lacked structural features. Scanning electron microscopy images showed a nearly perfect uniformity of the nanocellulosic coatings on PLA, and light transmittance results revealed remarkable transparency of the LbL-coated PLA films. The present work demonstrates the first ever LbL films based on high aspect ratio, water-dispersible nanofibrillated cellulose, and water-soluble carboxymethyl cellulose polymers that can be used as multifunctional films and coatings with tailorable properties, such as gas barriers and transparency. Owing to its flexibility, transparency and high-performance gas barrier properties, these thin film assemblies are promising candidates for several large-scale applications, including flexible electronics and renewable packaging.
|
|
| 22. |
|
|
| 23. |
|
|
| 24. |
- Aulin, Christian, 1980-, et al.
(author)
-
Wetting kinetics of oil mixtures on fluorinated model cellulose surfaces
- 2008
-
In: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 317:2, s. 556-567
-
Journal article (peer-reviewed)abstract
- The wetting of two different model cellulose surfaces has been studied; a regenerated cellulose (RG) surface prepared by spin-coating, and a novel multilayer film of poly(ethyleneimine) and a carboxymethylated microfibrillated cellulose (MFC). The cellulose films were characterized in detail using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). AFM indicates smooth and continuous films on a nanometer scale and the RMS roughness of the RG cellulose and MFC surfaces was determined to be 3 and 6 nm, respectively. The cellulose films were modified by coating with various amounts of an anionic fluorosurfactant, perfluorooctadecanoic acid, or covalently modified with pentadecafluorooctanyl chloride. The fluorinated cellulose films were used to follow the spreading mechanisms of three different oil mixtures. The viscosity and surface tension of the oils were found to be essential parameters governing the spreading kinetics on these surfaces. XPS and dispersive surface energy measurements were made on the cellulose films coated with perfluorooctadecanoic acid. A strong correlation was found between the surface concentration of fluorine, the dispersive surface energy and the contact angle of castor oil on the surface. A dispersive surface energy less than 18 mN/m was required in order for the cellulose surface to be non-wetting (Ξe > 90 °) by castor oil.
|
|
| 25. |
- Brooke, Robert, 1989-, et al.
(author)
-
Nanocellulose based carbon ink and its application in electrochromic displays and supercapacitors
- 2021
-
In: Flexible and Printed Electronics. - : IOP Publishing Ltd. - 2058-8585. ; 6:4
-
Journal article (peer-reviewed)abstract
- Conventional electronics have been highlighted as a very unsustainable technology; hazardous wastes are produced both during their manufacturing but also, due to their limited recyclability, during their end of life cycle (e.g. disposal in landfill). In recent years additive manufacturing processes (i.e. screen printing) have attracted significant interest as a more sustainable approach to electronic manufacturing (printed electronics). Despite the field of printed electronics addressing some of the issues related to the manufacturing of electronics, many components and inks are still considered hazardous to the environment and are difficult to recycle. Here we present the development of a low environmental impact carbon ink based on a non-hazardous solvent and a cellulosic matrix (nanocellulose) and its implementation in electrochromic displays (ECDs) and supercapacitors. As part of the reported work, a different protocol for mixing carbon and cellulose nanofibrils (rotation mixing and high shear force mixing), nanocellulose of different grades and different carbon: nanocellulose ratios were investigated and optimized. The rheology profiles of the different inks showed good shear thinning properties, demonstrating their suitability for screen-printing technology. The printability of the developed inks was excellent and in line with those of reference commercial carbon inks. Despite the lower electrical conductivity (400 S m-1 for the developed carbon ink compared to 1000 S m-1 for the commercial inks), which may be explained by their difference in composition (carbon content, density and carbon derived nature) compared to the commercial carbon, the developed ink functioned adequately as the counter electrode in all screen-printed ECDs and even allowed for improved supercapacitors compared to those utilizing commercial carbon inks. In this sense, the supercapacitors incorporating the developed carbon ink in the current collector layer had an average capacitance = 97.4 mF cm-2 compared to the commercial carbon ink average capacitance = 61.6 mF cm-2. The ink development reported herein provides a step towards more sustainable printed green electronics. © 2021 The Author(s).
|
|
| 26. |
- Brännvall, Elisabet, 1961-, et al.
(author)
-
CNFs from softwood pulp fibers containing hemicellulose and lignin
- 2022
-
In: Cellulose. - : Springer Science and Business Media B.V.. - 0969-0239 .- 1572-882X.
-
Journal article (peer-reviewed)abstract
- The energy demand to produce cellulose nanofibrils, CNFs, is high and additionally the cost of the starting material, the pulp, is substantial as high purity cellulose dissolving pulp is generally used. Pulps aimed for board and paper are produced at higher yield as they contain hemicelluloses and, in the case of unbleached pulp, lignin, and would be a more economical starting material for CNFs. It is of interest to understand how the presence of hemicellulose and lignin affects the fibrillation process and CNF properties. Kraft cooks of softwood were performed as well as kraft cooks with addition of polysulfide to increase the hemicellulose content. Part of the pulps were bleached to remove residual lignin, thus making it possible to compare pulps with and without lignin. Higher amount of hemicellulose had an obstructive effect on the enzymatic pre-treatment whereas lignin had no adverse effect on enzyme accessibility. Increased amount of charged groups improved the accessibility for enzymes. Both hemicellulose and lignin were carboxymethylated when pre-treatment by carboxymethylation was employed. However, carboxymethylation partly dissolved hemicelluloses. The tensile strength of CNF films was independent of the chemical composition of the pulp and the pre-treatment strategy. However, since the enzymatic pre-treatment decreased the cellulose DP more, CNF films from enzymatically pre-treated pulps had generally lower tensile strength. © 2022, The Author(s).
|
|
| 27. |
- Cervin, Nicholas Tchang, et al.
(author)
-
Ultra porous nanocellulose aerogels as separation medium for mixtures of oil/water liquids
- 2012
-
In: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 19:2, s. 401-410
-
Journal article (peer-reviewed)abstract
- A novel type of sponge-like material for the separation of mixed oil and water liquids has been prepared by the vapour deposition of hydrophobic silanes on ultra-porous nanocellulose aerogels. To achieve this, a highly porous (> 99%) nanocellulose aerogel with high structural flexibility and robustness is first formed by freeze-drying an aqueous dispersion of the nanocellulose. The density, pore size distribution and wetting properties of the aerogel can be tuned by selecting the concentration of the nanocellulose dispersion before freeze-drying. The hydrophobic light- weight aerogels are almost instantly filled with the oil phase when selectively absorbing oil from water, with a capacity to absorb up to 45 times their own weight in oil. The oil can also be drained from the aerogel and the aerogel can then be reused for a second absorption cycle.
|
|
| 28. |
|
|
| 29. |
- González-Gil, Rosa, et al.
(author)
-
Sustainable and Printable Nanocellulose-Based Ionogels as Gel Polymer Electrolytes for Supercapacitors
- 2022
-
In: Nanomaterials. - : MDPI. - 2079-4991. ; 12:2
-
Journal article (peer-reviewed)abstract
- A new gel polymer electrolyte (GPE) based supercapacitor with an ionic conductivity up to 0.32–0.94 mS cm−2 has been synthesized from a mixture of an ionic liquid (IL) with nanocellulose (NC). The new NC-ionogel was prepared by combining the IL 1-ethyl-3-methylimidazolium dimethyl phosphate (EMIMP) with carboxymethylated cellulose nanofibers (CNFc) at different ratios (CNFc ratio from 1 to 4). The addition of CNFc improved the ionogel properties to become easily printable onto the electrode surface. The new GPE based supercapacitor cell showed good electrochemical performance with specific capacitance of 160 F g−1 and an equivalent series resistance (ESR) of 10.2 Ω cm−2 at a current density of 1 mA cm−2. The accessibility to the full capacitance of the device is demonstrated after the addition of CNFc in EMIMP compared to the pristine EMIMP (99 F g−1 and 14.7 Ω cm−2). © 2022 by the authors.
|
|
| 30. |
- Karasu, Feyza, et al.
(author)
-
Organic-inorganic hybrid planarization and water vapor barrier coatings on cellulose nanofibrils substrates
- 2018
-
In: Frontiers in Chemistry. - : Frontiers Media SA. - 2296-2646. ; 6
-
Journal article (peer-reviewed)abstract
- Cellulose nanofibrils (CNF) can be produced in the form of thin, transparent andflexible films. However, the permeability of such materials to oxygen and water vaporis very sensitive to moisture, which limits their potential for a variety of packaging andencapsulation applications. Diffusion barrier coatings were thus developed to reducethe access of water molecules to enzymatically pre-treated and carboxymethylated CNFsubstrates. The coatings were based on UV curable organic-inorganic hybrids withepoxy, tetraethylorthosilicate (TEOS) and 3-glycidoxypropyltrimethylenesilane (GPTS)precursors and additional vapor formed SiNx layers. A total of 14 monolayer andmultilayer coatings with various thickness and hybrid composition were produced andanalyzed. The water vapor transmission rate (WVTR) of the bilayer epoxy/CNF film wastwo times lower compared to that of uncoated CNF film. This was partly due to the watervapor permeability of the epoxy, a factor of two times lower than CNF. The epoxy coatingimproved the transparency of CNF, however it did not properly wet to the CNF surfacesand the interfacial adhesion was low. In contrast hybrid epoxy-silica coatings led to highadhesion levels owing to the formation of covalent interactions through condensationreactions with the OH-terminated CNF surface. The barrier and optical performance ofhybrid coated CNF substrates was similar to that of CNF coated with pure epoxy. Inaddition, the hybrid coatings provided an excellent planarization effect, with roughnessclose to 1 nm, one to two orders of magnitude lower than that of the CNF substrates.The WVTR and oxygen transmission rate values of the hybrid coated CNF laminateswere in the range 5–10 g/m2/day (at 38◦C and 50% RH) and 3–6 cm3/m2/day/bar (at23◦C and 70% RH), respectively, which matches food and pharmaceutical packagingrequirements. The permeability to water vapor of the hybrid coatings wasmoreover foundto decrease with increasing the TEOS/GPTS ratio up to 30 wt% and then increase athigher ratio, and to be much lower for thinner coatings due to further UV-induced silanolcondensation and faster evaporation of byproducts. The addition of a single 150 nmthickSiNx layer on the hybrid coated CNF improved its water vapor barrier performance bymore than 680 times, with WVTR below the 0.02 g/m2/day detection limit.
|
|
| 31. |
- Koppolu, Rajesh, et al.
(author)
-
Tailoring the performance of nanocellulose-based multilayer-barrier paperboard using biodegradable-thermoplastics, pigments, and plasticizers
- 2023
-
In: Cellulose. - : Springer Science and Business Media B.V.. - 0969-0239 .- 1572-882X. ; 30:11, s. 6945-
-
Journal article (peer-reviewed)abstract
- In this work a multilayer barrier paperboard was produced in a roll-to-roll process by slot-die coating of nanocellulose (microfibrillated cellulose or carboxymethylated cellulose nanofibrils) followed by extrusion coating of biodegradable thermoplastics (polylactic acid, polybutylene adipate terephthalate and polybutylene succinate). Hyperplaty kaolin pigments were blended in different ratios into nanocellulose to tailor the barrier properties of the multilayer structure and to study their influence on adhesion to the thermoplastic top layer. Influence of a plasticizer (glycerol) on flexibility and barrier performance of the multilayer structure was also examined. Water vapor permeance for the multilayer paperboard was below that of control single-layer thermoplastic materials, and oxygen permeance of the coated structure was similar or lower than that of pure nanocellulose films. Glycerol as a plasticizer further lowered the oxygen permeance and kaolin addition improved the adhesion at the nanocellulose/thermoplastic interface. The results provide insight into the role played by nanocelluloses, thermoplastics, pigments, and plasticizers on the barrier properties when these elements are processed together into multilayer structures, and paves the way for industrial production of sustainable packaging.
|
|
| 32. |
- Lindström, Tom, et al.
(author)
-
Market and technical challenges and opportunities in the area of innovative new materials and composites based on nanocellulosics
- 2014
-
In: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 29:4, s. 345-351
-
Journal article (peer-reviewed)abstract
- This communication is a review over the major market and technical challenges and opportunities for nanocellulosic materials on a large scale but in low-to-medium-end markets. Basically, the potential use of nanocellulose as a wet-end strength additive in papermaking has been known for decades, but not come into operation because of the high-energy costs of producing these materials. Cost performance compared to starch derivatives is one challenge, and the other is to design suitable dewatering/retention aid systems. Other paper applications are as a surface-sizing agent and as a barrier coating material. Major challenges are associated with the high viscosity of nanocellulosic materials and how to apply the nanocellulose in order to obtain good surface coverage. There are several opportunities in the nanocomposite markets. The packaging sector together with the automotive sector and the building sector constitute large potential markets. Challenges are related to the mixing of hydrophobic and hydrophilic materials so that a good dispersion of nanocellulose is obtained. Scaling up of nanocellulose production processes and procedures for nanocomposite manufacturing in order to obtain price-performance in the various applications remains, as expected, the largest challenge.
|
|
| 33. |
- Lindström, Tom, et al.
(author)
-
The emergence of practical nanocellulose applications for a more sustainable paper/board industry
- 2014
-
In: IPPTA: Quarterly Journal of Indian Pulp and Paper Technical Association. - 0379-5462. ; 26:1, s. 53-61
-
Journal article (peer-reviewed)abstract
- There has been extensive research and development activities in the field of nanofibrillated cellulose (NFC) materials during recent years, although microfibrillated cellulose was developed already during the late 1970s at ITT-Rayonier in USA. A major impediment for the large-scale use of NFC has been the high-energy use (excess of 30000 kWh/ton NFC in energy consumption). This problem has now been alleviated by a series of different pre-treatment procedures of the fibres prior to the subsequent mechanical cell wall delamination. The focus in practical papermaking applications of NFC is in the reinforcement of paper/board materials (dry strength wet-end additive) and in barrier coating applications. The driving forces in these applications are resource and energy efficiency in papermaking and the vision of substituting fossil-based films with nanocellulose barriers. Nanocellulose has excellent oil, fat and oxygen barrier properties in the dry state, but the oxygen barrier properties deteriorate at high relative humidities and the approaches to alleviate the moisture sensitivity will be discussed. Today, there are many companies in the process of commercializing NFC and several of them have pilot plants/pre-commercial operations and are planning for up scaling. A pilot plant for the nominal production of 100 kg/day (dry based NFC) was also taken into operation at Innventia AB in 2010. The current contribution will highlight critical issues in the production of NFC and discuss various applications and hurdles to be overcome in order to make NFC production for paper/board based end-use applications viable.
|
|
| 34. |
- Martinez-Crespiera, Sandra, et al.
(author)
-
Use of Nanocellulose to Produce Water-Based Conductive Inks with Ag NPs for Printed Electronics
- 2022
-
In: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 23:6
-
Journal article (peer-reviewed)abstract
- The need for more sustainable printed electronics has emerged in the past years. Due to this, the use of nanocellulose (NC) extracted from cellulose has recently been demonstrated to provide interesting materials such as functional inks and transparent flexible films due to its properties. Its high specific surface area together with the high content of reactive hydroxyl groups provide a highly tailorable surface chemistry with applications in ink formulations as a stabilizing, capping, binding and templating agent. Moreover, NC mechanical, physical and thermal properties (high strength, low porosity and high thermal stability, respectively) provide an excellent alternative for the currently used plastic films. In this work, we present a process for the production of water-based conductive inks that uses NC both as a template for silver nanoparticles (Ag NPs) formation and as an ink additive for ink formulation. The new inks present an electrical conductivity up to 2 × 106 S/m, which is in the range of current commercially available conductive inks. Finally, the new Ag NP/NC-based conductive inks have been tested to fabricate NFC antennas by screen-printing onto NC-coated paper, demonstrating to be operative.
|
|
| 35. |
- Ojamäe, Lars, 1964-, et al.
(author)
-
IR and quantum-chemical studies of carboxylic acid and glycine adsorption on rutile TiO2 nanoparticles
- 2006
-
In: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 296:1, s. 71-78
-
Journal article (peer-reviewed)abstract
- Nanocrystalline TiO2 powders of the rutile polymorph, synthesized by a sol–gel method, were treated with water solutions containing, respectively, formic, acetic, and citric acid and glycine in order to study the adsorption properties of these organic species. The samples were characterized by FTIR, Raman, powder XRD, and TEM. It was found that HCOOH, CH3COOH and HOC(COOH)(CH2COOH)2—but not NH2CH2COOH—adsorbed onto TiO2. The adsorption of HCOOH, CH3COOH and NH2CH2COOH onto the (110) surface of rutile was also studied by quantum-chemical periodic density functional theory (DFT) calculations. The organic molecules were from the computations found to adsorb strongly to the surfaces in a bridge-coordinating mode, where the two oxygens of the deprotonated carboxylic acid bind to two surface titanium ions. Surface relaxation is found to influence adsorption geometries and energies significantly. The results from DFT calculations and ab initio molecular-dynamics simulations of formic acid adsorption onto TiO2 are compared and match well with the experimental IR measurements, supporting the bridge-binding geometry of carboxylic-acid adsorption on the TiO2 nanoparticles.
|
|
| 36. |
- Redlinger-Pohn, Jakob D., et al.
(author)
-
Mechanisms of Cellulose Fiber Comminution to Nanocellulose by Hyper Inertia Flows
- 2022
-
In: ACS Sustainable Chemistry and Engineering. - : American Chemical Society. - 2168-0485. ; 10:2, s. 703-719
-
Journal article (peer-reviewed)abstract
- Nanocelluloses are seen as the basis of high-performance materials from renewable sources, enabling a bio-based sustainable future. Unsurprisingly, research has initially been focused on the design of new material concepts and less on new and adapted fabrication processes that would allow large-scale industrial production and widespread societal impact. In fact, even the processing routes for making nanocelluloses and the understanding on how the mechanical action fibrillates plant raw materials, albeit chemically or enzymatically pre-treated, are only rudimentary and have not evolved significantly during the past three decades. To address the challenge of designing cellulose comminution processes for a reliable and predictable production of nanocelluloses, we engineered a study setup, referred to as Hyper Inertia Microfluidizer, to observe and quantify phenomena at high speeds and acceleration into microchannels, which is the underlying flow in homogenization. We study two different channel geometries, one with acceleration into a straight channel and one with acceleration into a 90° bend, which resembles the commercial equipment for microfluidization. With the purpose of intensification of the nanocellulose production process, we focused on an efficient first pass fragmentation. Fibers are strained by the extensional flow upon acceleration into the microchannels, leading to buckling deformation and, at a higher velocity, fragmentation. The treatment induces sites of structural damage along and at the end of the fiber, which become a source for nanocellulose. Irrespectively on the treatment channel, these nanocelluloses are fibril-agglomerates, which are further reduced to smaller sizes. In a theoretical analysis, we identify fibril delamination as failure mode from bending by turbulent fluctuations in the flow as a comminution mechanism at the nanocellulose scale. Thus, we argue that intensification of the fibrillation can be achieved by an initial efficient fragmentation of the cellulose in smaller fragments, leading to a larger number of damaged sites for the nanocellulose production. Refinement of these nanocelluloses to fibrils is then achieved by an increase in critical bending events, i.e., decreasing the turbulent length scale and increasing the residence time of fibrils in the turbulent flow. © 2022 The Authors.
|
|
| 37. |
- Rosén, Tomas, 1985-, et al.
(author)
-
Cross-Sections of Nanocellulose from Wood Analyzed by Quantized Polydispersity of Elementary Microfibrils
- 2020
-
In: ACS Nano. - : American Chemical Society. - 1936-0851 .- 1936-086X. ; 14:12, s. 16743-16754
-
Journal article (peer-reviewed)abstract
- Bio-based nanocellulose has been shown to possess impressive mechanical properties and simplicity for chemical modifications. The chemical properties are largely influenced by the surface area and functionality of the nanoscale materials. However, finding the typical cross-sections of nanocellulose, such as cellulose nanofibers (CNFs), has been a long-standing puzzle, where subtle changes in extraction methods seem to yield different shapes and dimensions. Here, we extracted CNFs from wood with two different oxidation methods and variations in degree of oxidation and high-pressure homogenization. The cross-sections of CNFs were characterized by small-angle X-ray scattering and wide-angle X-ray diffraction in dispersed and freeze-dried states, respectively, where the results were analyzed by assuming that the cross-sectional distribution was quantized with an 18-chain elementary microfibril, the building block of the cell wall. We find that the results agree well with a pseudosquare unit having a size of about 2.4 nm regardless of sample, while the aggregate level strongly depends on the extraction conditions. Furthermore, we find that aggregates have a preferred cohesion of phase boundaries parallel to the (110)-plane of the cellulose fibril, leading to a ribbon shape on average.
|
|
| 38. |
- Salomonsson, Anette, et al.
(author)
-
Nanocrystalline Ruthenium oxide and Ruthenium in sensing applications -an experimental and theoretical study
- 2006
-
In: Journal of Nanoparticle Research. - : Springer Science and Business Media LLC. - 1388-0764 .- 1572-896X. ; 8:6, s. 899-910
-
Journal article (peer-reviewed)abstract
- In this project, we have explored RuO2 and Ru nanoparticles (∼ ∼10 and ∼ ∼5 nm, respectively, estimated from XRD data) to be used as gate material in field effect sensor devices. The particles were synthesized by wet chemical procedure. The capacitance versus voltage characteristics of the studied capacitance shifts to a lower voltage while exposed to reducing gases. The main objectives are to improve the selectivity of the FET sensors by tailoring the dimension and surface chemistry of the nanoparticles and to improve the high temperature stability. The sensors were characterized using capacitance versus voltage measurements, at different frequencies, 500 Hz to 1 MHz, and temperatures at 100–400°C. The sensor response patterns have been found to depend on operating temperature. X-ray photoelectron spectroscopy (XPS) analyses were performed to investigate the oxidation state due to gas exposure. Quantum-chemical computations suggest that heterolytic dissociative adsorption is favored and preliminary computations regarding water formation from adsorbed hydrogen and oxygen was also performed.
|
|
| 39. |
- Salomonsson, Anette, et al.
(author)
-
Nanoparticles for long-term stable, more selective MISiCFET gas sensors
- 2005
-
In: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 107:2, s. 831-838
-
Journal article (peer-reviewed)abstract
- Synthesis of metal-oxide nanoparticles and utilization of these particles as gate materials for field-effect sensor devices is reported. Improved selectivity to specific gases is expected by modulating the size of the oxide nanoparticles or impregnating them with catalytic metals. Another objective is to improve the long-term thermal stability of the sensors, since the metal loaded nanoparticles may prevent thermally induced restructuring of the gate layer, which is often a problematic issue for the catalytic metal layers. Because of its reasonably high electrical conductivity, which is especially important for the capacitive gas sensors, ruthenium dioxide has been identified to be one of the potential candidates as gate material for the field-effect sensor devices. Interestingly, this material has been found to change its resistivity in different gaseous ambients. When used as a gate material, sensitivity to reducing gases has been observed for the RuO2/SiO2/4H-SiC capacitors. Changes in the resistivity of the films due to various gas exposures have also been recorded. Morphological studies of nanoparticles (SiO2 and Al2O3), loaded or impregnated with catalytic metals (e.g. Pt), have been performed.
|
|
| 40. |
- Salomonsson, Anette, et al.
(author)
-
Ruthenium dioxide & Ru Nanoparticles for MISiCFET gas sensors
- 2005
-
In: Nanotech 2005 (NSTI) Anaheim, USA, 8-12 May. ; , s. 269–272-
-
Conference paper (peer-reviewed)abstract
- Catalytically active nanoparticles used as gate material on SiC-FET gas sensors. The goal is to improve the selsectivity and senstitivty.The sensors are sensitive towards oxidising and reducing gases (H2, NH3, C3H6).
|
|
| 41. |
|
|
| 42. |
- Srinivasa, Prashanth, et al.
(author)
-
Experimental characterisation of nanofibrillated cellulose foams
- 2015
-
In: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 22:6, s. 3739-3753
-
Journal article (peer-reviewed)abstract
- There is a growing interest in applications for nanofibrillated cellulose based materials owing to their exceptional mechanical properties. Nanofibrillated cellulose (NFC) foam is one such derivative which has potential applications in a wide array of fields. Here, we characterise the mechanical properties of two particular high porosity NFC foams (98.13 and 98.96 %) prepared by a freeze drying process. We evaluate their behaviour in uni-axial and bi-axial compression with cyclic loading. The secondary loading cycles reveal complete irreversible damage of the microstructure, with the secondary loading path being characterised by near zero plateau stress. In force controlled tests, negligible hysteresis corroborates the idea that there is no energy dissipation owing to near complete microstructural damage. Furthermore, we observe no indications of preferential orientation of the microstructure in these tests. The stress responses in mutually perpendicular directions are seen to be identical, within statistical considerations. We then utilise the “pseudo-elastic” model developed and adopt it to the case of highly compressible Ogden strain energy formulation with a modified neo-Hookean for the unloading, with a view of fitting a continuum hyperelastic model to the experimental data. The material parameters obtained from uni-axial data are seen to be insufficient to describe the more general bi-axial deformation. The parameters obtained from the bi-axial test describe uni-axial deformation up to stretches of ~0.5 but overestimate the stress levels beyond that point.
|
|
| 43. |
- Sudheshwar, A., et al.
(author)
-
Assessing sustainability hotspots in the production of paper-based printed electronics
- 2023
-
In: Flexible and Printed Electronics. - : Institute of Physics. - 2058-8585. ; 8:1
-
Journal article (peer-reviewed)abstract
- Novel printed electronics are projected to grow and be manufactured in the future in large volumes. In many applications, printed electronics are envisaged as sustainable alternatives to conventional (PCB-based) electronics. One such application is in the semi-quantitative drug detection and point-of-care device called ‘GREENSENSE’ that uses paper-based printed electronics. This paper analyses the carbon footprint of GREENSENSE in order to identify and suggest means of mitigating disproportionately high environmental impacts, labeled ‘sustainability hotspots’, from materials and processes used during production which would be relevant in high-volume applications. Firstly, a life cycle model traces the flow of raw materials (such as paper, CNCs, and nanosilver) through the three ‘umbrella’ processes (circuit printing, component mounting, and biofunctionalization) manufacturing different electronic components (the substrate, conductive inks, energy sources, display, etc) that are further assembled into GREENSENSE. Based on the life cycle model, life cycle inventories are modeled that map out the network of material and energy flow throughout the production of GREENSENSE. Finally, from the environmental impact and sustainability hotspot analysis, both crystalline nanocellulose and nanosilver were found to create material hotspots and they should be replaced in favor of lower-impact materials. Process hotspots are created by manual, lab-, and pilot-scale processes with unoptimized material consumption, energy use, and waste generation; automated and industrial-scale manufacturing can mitigate such process hotspots. © 2023 The Author(s).
|
|
| 44. |
- Verney, Julien, et al.
(author)
-
Combined lower body endurance and upper body resistance training improves performance and health parameters in healthy active elderly
- 2006
-
In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 97:3, s. 288-297
-
Journal article (other academic/artistic)abstract
- We investigated the effects of combined lower body (LB) endurance and upper body (UB) resistance training on endurance, strength, blood lipid profile and body composition in active older men. Ten healthy still active men (73+/-4 years, V(O2) peak: 36 (31-41) ml min-1 kg-1) were tested before and after 14 weeks of combined training (3 times week-1). Training consisted of 3x12 min of high intensity interval training on a bicycle for endurance interspersed by 3x12 min of UB resistance exercises. V(O2) peak during leg cycling and arm cranking, isokinetic torque of knee extensor and shoulder abductor and the cross-sectional area (CSA) of several muscles from UB and LB were measured. Sagittal abdominal diameter (SAD) and abdominal fat area were measured on MRI scans. Total body composition was assessed by hydrostatic weighing (HW) and dual-energy X-ray absorptiometry (DEXA). Blood lipid profile was assessed before and after training. By the end of the training period, V(O2) peak (l min-1) increased significantly by 9 and 16% in leg cycling and arm cranking tests, respectively. Maximal isokinetic torque increased both for the knee extensor and shoulder abductor muscle groups. CSA increased significantly in deltoid muscle. Percentage of body fat decreased by 1.3% (P<0.05) and abdominal fat and SAD decreased by 12 and 6%, respectively (P<0.01). There was also a significant decrease in total cholesterol and low-density lipoprotein. Thus, combined LB endurance and UB resistance training can improve endurance, strength, body composition and blood lipid profile even in healthy active elderly.
|
|
| 45. |
- Verney, Julien, et al.
(author)
-
Effects of combined lower body endurance and upper body resistance training on the satellite cell pool in elderly subjects
- 2008
-
In: Muscle and Nerve. - : Wiley. - 0148-639X .- 1097-4598. ; 38:3, s. 1147-1154
-
Journal article (peer-reviewed)abstract
- To distinguish the respective potential of endurance and resistance training to increase the satellite cell pool, we investigated the effects of 14 weeks of concurrent lower body endurance and upper body resistance training (3 sessions/week) on vastus lateralis (VLat) and deltoid (Del) muscles of 10 active elderly men. NCAM+ satellite cells and myonuclear number were assessed in VLat and Del. After 14 weeks of training the NCAM+ satellite cell pool increased similarly (+38%) in both muscles, mainly in type II muscle fibers (P < 0.05). There was no significant change in myonuclear number or myonuclear domain in either muscle. Combining resistance training in the upper limbs with endurance training in the lower limbs is an efficient strategy to enhance the satellite cell pool in upper and lower body muscles in elderly subjects. Our results provide a practical reference for the determination of optimal exercise protocols to improve muscle function and regeneration in the elderly.
|
|
