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  • 101.
    Wiklund, Hanna
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Lattice Boltzmann simulations of two-phased flow in fibre network systems2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Two-phase flow in microfluidic systems is of great interest for many scientificand engineering problems. Especially in the pulp and paper area, the problems spanfrom fibre-fibre interactions in the consolidation process of papermaking to edgewickingin paper board during the aseptic treatment of liquid packaging.The objective of this thesis is to gain a fundamental understanding of the microfluidicmechanisms that play a significant role in various problems of two-phaseflow in fibre networks. To achieve this objective a new method for the treatment ofwetting boundary conditions in the lattice Boltzmann model has been developed.The model was validated and compared with the previous treatments of wettingboundary conditions, by using two test cases: droplet spreading and capillary intrusion.The new wetting boundary condition was shown to give more accurate resultsfor a wider range of contact angles than previous methods, and capillary intrusioncould be simulated with higher accuracy even at a relatively low resolution.As an application of the developed method, two examples of two-phase flowproblems in fibre networks are taken: the shear resistance of liquid bridges, as relatedto the wet web strength, and liquid penetration into porous structures, as related toedge-wicking in paper board. The shear resistance force was shown to depend verylittle on surface tension and contact angle. Instead, the shear resistance is a dynamicforce and a major contributing factor is the distortion of the flow field caused bythe presence of interfaces. This distortion of the flow field is size-dependent: thesmaller the bridge, the larger the proportion of the distorted flow field and thus alarger shear resistance force per unit width. In other words, multiple small bridgeshave an enhancement effect on shear resistance. The results from the simulations ofliquid penetration into porous structures showed that the discontinuities in the solidsurfacecurvature, as are present in the formof corners on the capillary surfaces, havestrong influences on liquid penetration through their pinning effects and also theirinteractions with local geometry. The microtopography can therefore, accelerate,decelerate and, in some cases, even stop the liquid penetration into random porousmedia.

  • 102.
    Wiklund, Hanna
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Uesaka, Tetsu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Edge-wicking: Micro-fluidics of two-dimensional liquid penetrationinto porous structures2012In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 2, p. 403-408Article in journal (Refereed)
    Abstract [en]

    We have performed free-energy-based two-dimensional lattice Boltzmann simulations of the penetration of liquid into the edge of a porous material. The purpose was to gain further insight into possible mechanisms involved in the penetration of liquid into the unsealed edges of paper and paper board. In order to identify the fundamental mechanisms we have focused on a model structure that consists of a network of interconnected capillaries. Two different mechanisms were identified: pinning at corners of solid surfaces and increased pressure in dead-end pores. These mechanisms significantly decelerate or even stop the liquid penetration into the porous structures.

  • 103.
    Wiklund, Hanna
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Uesaka, Tetsu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Simulations of shearing of capillary bridges2012In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 136, no 9, p. Art. no. 094703-Article in journal (Refereed)
    Abstract [en]

    Capillary bridges are considered as the major source of interaction forces acting in wet particulate systems. We study the dynamic shear resistance by using a lattice Boltzmann numerical scheme for a binary fluid. The shear resistance force showed very little dependence on surface tension and contact angle. Instead, the shear resistance is a dynamic phenomenon and a major contributing factor is the distortion of the flow field caused by the presence of interfaces. This distortion of the flow field is geometry-dependent: in smaller diameter bridges the proportion of this distorted flow field becomes larger and it makes a major contribution to the shear resistance force. In other words multiple bridges have an enhancement effect on shear resistance.

  • 104.
    Zasadowski, Dariusz
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    REMOVAL OF LIPOPHILIC EXTRACTIVES AND MANGANESE IONS FROM SPRUCE TMP WATER BY FLOTATION2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Dissolved and Colloidal substances (DisCo) and metals are released from wood during thermomechanical pulp (TMP) production. The mechanical treatment causes that these components have a tendency to accumulate in process waters, as the water circulation systems in integrated paper mills are being closed. Disturbances such as pitch depositions on the paper machine (pitch problems), specks in the paper, decreased wet and dry strength, interference with cationic process chemicals, and impaired sheet brightness and friction properties appear in the presence of DisCo substances. The presence of transition metal ions such as manganese results in higher consumption of bleaching chemicals (hydrogen peroxide) and lowers the optical quality of the final product, and addition of complexing agents, such as EDTA or DTPA, to prevent this is needed. The never ending trends to decrease water consumption and increase process efficiency in pulp and paper production stress that it is very important both to know the effects of wood substances on pulping and papermaking and to be able to remove them in an efficient way.

    Carried out investigations presented in this thesis show that the lipophilic extractives can be removed from TMP press water to high extent. A 90% decrease in turbidity and a 91% removal of lipophilic extractives from TMP press water can be obtained by addition of a cationic surfactant as foaming agent during flotation. Additionally, fibres located in TMP press water are not removed with the foam fraction but purified. A retained concentration of hydrophilic extractives in the process water indicates that the flotation is selective. Moreover, by introduction of a new recoverable surface active complexing agent, a chelating surfactant, manganese ions in the form of chelates can be successfully removed from the pulp fibres and separated from the process water in the same flotation process.

    iii

    The findings presented above indicate new possibilities for internal water cleaning and decreased emissions to water if flotation technology is applied in an integrated mechanical pulp mill.

  • 105.
    Zasadowski, Dariusz
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Hedenström, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Edlund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Removal of lipophilic extractives and manganese ions from spruce TMP waters in a customized flotation cell2012In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, no 2, p. 2376-2392Article in journal (Refereed)
    Abstract [en]

    The influence of a chelating surfactant, different foaming agents, cationic polyelectrolytes, pH value, and temperature on the purification efficiency of process waters from a mechanical pulp mill has been studied by flotation in a 1 L customized unit. Turbidity measurements and gas chromatography (GC) were carried out to determine the removal and characteristics of dissolved and colloidal substances (DisCo). The manganese ion content in the process waters before flotation and the metal chelate removal capacity by flotation were determined by Inductively Coupled Plasma (ICP) and Atomic Absorption Spectrometry (AAS) measurements. It was found that a 99% removal of complex bound manganese ions and a 94% decrease in turbidity of the TMP water produced at the laboratory can be achieved in a single-stage flotation with a chelating surfactant and a foaming agent. Furthermore, a 91% decrease in turbidity, the removal of up to 96% of resin and fatty acids, and 93% of triglycerides from TMP water can be obtained after application of a foaming agent.

  • 106.
    Zasadowski, Dariusz
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Hedenström, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Edlund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Use of a Voith flotation cell for removal of lipophilic extractives and Mn ions from spruce thermomechanical pulping process waters2012In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, no 3, p. 2784-2126Article in journal (Refereed)
    Abstract [en]

    The effects of a chelating surfactant and different foaming agents on the efficiency of cleaning process waters from a thermomechanical pulp (TMP) mill were studied in a Voith flotation cell. Turbidity measurements and gas chromatography were used to determine the removal extent and characteristics of dissolved and colloidal substances (DisCo). The metal ion content in the process waters before flotation and the metal chelate removal after flotation were determined using inductively coupled plasma-optical emission spectrometry (ICP-OES). FiberLab (TM) equipment was used to characterize changes in the size of fibers present in the process waters. The results indicate that a decrease in turbidity of up to 91% and the removal of 80% of lipophilic extractives in the TMP water could be obtained using a single-stage flotation unit. Furthermore, the foam fraction was within 5% of the initial volume, and 100% of the Mn2+/chelating surfactant complex added to the TMP water was removed.

  • 107.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Simple Fabrication of Gold Nanobelts and Patterns2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 1, p. Art. no. e30469-Article in journal (Refereed)
    Abstract [en]

    Gold nanobelts are of interest in several areas; however, there are only few methods available to produce these belts. We report here on a simple evaporation induced self-assembly (EISA) method to produce porous gold nanobelts with dimensions that scale across nanometer (thickness ~80 nm) and micrometer (width ~20 μm), to decimeter (length ~0.15 m). The gold nanobelts are well packed on the beaker wall and can be easily made to float on the surface of the solution for depositing onto other substrates. Microscopy showed that gold nanobelts had a different structure on the two sides of the belt; the density of gold nanowires on one side was greater than on the other side. Electrical measurements showed that these nanobelts were sensitive to compressive or tensile forces, indicating a potential use as a strain sensor. The patterned nanobelts were further used as a template to grow ZnO nanowires for potential use in applications such as piezo-electronics. © 2012 Zhang et al.

  • 108.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Size and concentration controlled growth of porous gold nanofilm2012In: Physica status solidi. A, Applied research, ISSN 0031-8965, E-ISSN 1521-396X, Vol. 209, no 3, p. 519-523Article in journal (Refereed)
    Abstract [en]

    At an air/water interface, diffusion-limited aggregation (DLA) of gold nanoparticles can form porous gold thin films. This porous film roughly consists of a network of irregular nanowires. For this air–water system, external parameters like temperature are well studied, while the influence of internal parameters, e.g., the size and concentration of the nanoparticles, have not been studied in detail. Here, we report on the growth of porous gold nanofilms for different nanoparticle sizes and concentrations to get a relationship between the morphology of the films and the internal parameters. The gold nanoparticles were synthesized by reducing HAuCl4 using sodium citrate. Transmission electron microscopy (TEM) characterization

    showed a linear relation between the formed gold nanowires and the concentration of HAuCl4 if the concentration of sodium citrate is unchanged. A linear dependency was also found between the wire diameter and the gold nanoparticle concen- tration, and between the wire diameter and volume fraction of the nanoparticles. The electrical resistance of the films was measured, showing a linear relation between resistance and the inverse of the cross-sectional area of the nanowires. This study shows the relation between the morphology and resistance of the grown porous films and the controllable internal parameters that will be useful in further exploration of this thin-film growth method.

  • 109.
    Zhang, Renyun
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Carbon nanomaterials as drug carriers: Real time drug release investigation2012In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 32, no 5, p. 1247-1252Article in journal (Refereed)
    Abstract [en]

    The use of carbon nanomaterials in biomedical applications and the cytotoxicity of these materials have been areas of great interest during the last decade. In vitro drug load and release, as well as in vivo animal tests, have been carried out using carbon nanomaterials. However, no comparison studies on the drug load and the release of different carbon nanomaterials have been reported. Here, we report on a real time investigation of the drug release of carbon black (CB) nanoparticles, carbon nanotubes (CNTs) and graphene oxide (GO), using rhodamine B (RB) as a model of drug. The binding of RB to the nanomaterials were characterized by FTIR and UV-vis. The mass loading capacities of these nanomaterials were also studied, showing that GO had the highest capacity. The real time drug release experiment indicated different accumulative release modes of these nanomaterials at different pH values, due to their different binding modes with RB, which is also discussed as being the reason for the mechanism differences. Moreover, the comparison of the drug release capacity of CNT-RB and f-CNT-RB (functionalized-CNT-RB) indicated an influence of hydrogen bonds in both drug loading and release, as the hydrogen bonds increased the loading capacity of the carbon nanotube after acid treatment and changed the drug release mechanism at pH 7.4. Thus, here we identified the drug release modes of the different carbon nanomaterials. The results of the influence of functional groups and hydrogen bonds point also out a potential way of controlling the drug release behavior of carbon nanomaterials by surface modification. © 2012 Elsevier B.V. All rights reserved.

  • 110.
    Zimmerman, Jenny K. M.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    LOCAL ENGAGEMENT - A PREREQUISITE FOR SUCCESSFUL REINTRODUCTION2012Conference paper (Refereed)
  • 111.
    Zimmerman, Jenny K. M.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Noble Crayfish (Astacus astacus) in a Changing World: Implications for Management2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The noble crayfish (Astacus astacus) is critically endangered in Sweden. This is mainly due to the crayfish plague (Aphanomyces astaci), a lethal disease that, among other things, can be spread through the stocking of fish from contaminated water or contaminated fishing gear. The largest single propagation path is the illegal introduction of infected signal crayfish (Pacifastacus leniusculus). A conservation measure for crayfish is to re-introduce it to where it has a chance to survive, though a sustainable, locally regulated fishing can also serve as an indirect protection for the species. When the local inhabitants are allowed to keep their fishing culture and when fishing is acceptable, the incentive for illegal stocking of signal crayfish is low. However, it is important to avoid overfishing because the recovery, especially in the northern regions, can take several years. Therefore, it is important to know how crayfish respond long-term to fishing and environmental factors.

    Crayfish populations became extinct in the River Ljungan for unknown reasons in 1999. The water flow of the river has been used for activities such as fishing, timber transport and hydroelectric power since the 1500s, and the noble crayfish has been part of the fauna since the last century. The River Ljungan was known as one of Sweden's best fishing areas for crayfish and fishing became an important part of the local tradition. When the crayfish populations became extinct, a reintroduction program was a natural step, and crayfish are nowadays re-established in the river.

    From 1963 to 1990 the Swedish Board of Fisheries collected data from crayfish fishing in the River Ljungan to determine the economic damage to fishery owners caused by the construction of a power plant. After each season the fishermen reported the catch. In this thesis, the data was used to investigate which factors influence the long-term size of the crayfish catch and how the crayfish catches were affected by the power plant building. After re-introduction of the crayfish to the River Ljungan, the local fishermen monitored the population development in a simple, standardized way. To examine the validity of their measurements and to investigate the body growth of the individuals, a capture-recapture technique with a permanent marking of the crayfish was used.

    The crayfish catches were primarily impacted by the previous years' catch size, and a large catch the previous year resulted in a reduced catch the following year. A mild winter climate (NAO-index > -0.7) six years before the catch implied a large catch, whereas a high water flow during the autumn or spring (>95m3s-1) two years before the catch, implied a poor catch. Major habitat changes in the form of greatly reduced water flow (~90%) were negative for crayfish catches. The standardized method of fishing used by the local fishermen to monitor the development of the crayfish population was precise enough to detect population trends and this method can therefore be recommended to monitor future re-introductions of crayfish. Although the River Ljungan is located at the northern edge of the species' range, noble crayfish in the river presently have a body growth rate that is close to the maximum measured for crayfish (8 mm/moult for females and 10 mm/moult for males).

    Based on the results, the most important advice for sustainable fisheries in Ljungan and other northern rivers is to:

    • Monitor the population trends, NAO-index and water flow in May and October. 
    • Use the results from the monitoring to determine the number of allowed fishing days and traps.
    • Collect data about the catch size and efforts from legal fishing and use it to evaluate the sustainability of the fishing.
    • Enhance the buildup of the harvestable cohort by

    -saving reproductive females

    -introduce a size limit of 10 cm

    -provide proper shelters for the non-harvestable cohort.

  • 112.
    Zimmerman, Jenny K. M.
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Palo, R Thomas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Time series analysis of climate-related factors and their impact on a red-listed noble crayfish population in northern Sweden2012In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 57, no 5, p. 1031-1041Article in journal (Refereed)
    Abstract [en]

    1. Global climate change is predicted to raise water temperatures and alter flow regimes in northern river systems. Climate-related factors might have profound impacts on survival, reproduction and distribution of freshwater species such as red-listed noble crayfish (Astacus astacus) in its northern limit of distribution.2. In this study, noble crayfish capture data over 27 years from the River Ljungan, Sweden, were examined. Time series of catch per unit effort (CPUE) were analysed in relation to the North Atlantic Oscillation (NAO) index, regional weather factors and water flow. CPUE was assumed to reflect differences in population size. Two models were constructed to explore the relative impact of different climate factors and density dependence on variability of catch sizes.3. The most parsimonious model for CPUE time series, explaining 72% of the variance in CPUE, included density-dependent population dynamics of the crayfish and climate or weather factors. The specific effect from density dependence in the model was 37%, while climate/weather factors contributed with 35% of the variation. The most important climate/weather factors are variations in NAO index and water flow. Temperature did not improve the model fit to capture data.4. The best model was evaluated using independent data sets that gave correlations between model predictions and data ranging from 0.44 to 0.53. The density dependence shows a time lag of 1 year, while climate variables show time lags from 2 to 6 years in relation to CPUE, indicating effects on different cohorts of the crayfish population.5. Both density dependence and climatic factors play a significant role in population fluctuations of noble crayfish. A 6-year time lag for NAO index is puzzling but indicates that some as yet unidentified factors related to NAO might act on the juvenile stages of the population. Water flow shows a 2-year lag to the CPUE, and high flow in the river may affect adult survival. The reasons for fluctuation of crayfish catches in response to climate need to be identified, and fishing quotas should consider the different cohort sizes because of variation in environment. Reintroduction programmes for crayfish need to consider effects of climate change when designing management strategies.

  • 113.
    Zimmerman, Jenny K. M.
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Palo, R Thomas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    WHERE SHOULD YOU PUT THE CRAYFISH - DOES THE ACTUAL REINTRODUCTION SITE MATTER?2012Conference paper (Refereed)
  • 114.
    Öberg, Lisa
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Kullman, Leif
    Institutionen för ekologi, miljö och geovetenskap, Umeå universitet.
    Contrasting short-term performance of mountain birch (Betula pubescens ssp. czerepanovii) treeline along a latitudinal continentality-maritimity gradient in the southern Swedish Scandes2012In: Fennia, ISSN 0015-0010, Vol. 190, no 1, p. 19-40Article in journal (Refereed)
    Abstract [en]

    Positional treeline shift is a fundamental aspect and indicator of high-mountain vegetation response to climate change. This study analyses treeline performance during the period 2005/2007 -2010/2011 in the Swedish Scandes. Focus is on mountain birch (Betula pubescens ssp. czerepanovii) along a regional climatic maritimity-continentality gradient. Treeline upshift by 3.0 yr-1 in the maritime part differed significantly from retreat by 0.4 m yr-1 in the continental part of the transect. This discrepancy is discussed in terms of differential warming-induced snow cover phenology patterns and their influence on soil moisture conditions. In the continental area, earlier and more complete melting of prior relatively rare late-lying snow patches, even high above the treeline, has progressed to a state when melt water irrigation ceases. As a consequence, soil drought sets back the vigor of existing birches and precludes sexual regeneration and upslope advance of the treeline. In the maritime area, extensive and deep snow packs still exist above the treeline and constrain its position, although some release is taking place in the current warm climate. Thereby, the birch treeline expands upslope as the alpine snow patches shrink, but continue to provide sufficient melt water throughout the summer. Treeline rise appears to have been based primarily on seed regeneration over the past few decades. This is a novelty, since prior (1915-2007) treeline advance was accomplished mainly by in situ shifts in growth form of relict krummholz birches, in some cases millennial-old, prevailing above the treeline. By the snow phenology mechanism, birch can benefit from climate warming in the maritime region, which contrasts with the situation in the continental region. This discrepancy should be accounted for in projective models. In a hypothetical case of sustained warming, the subalpine birch forest belt may expand less extensively than often assumed, although advance may continue for some time in snow rich maritime areas.

  • 115.
    Öberg, Lisa
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Kullman, Leif
    Umeå University, Department of Ecology and Environmental Science, SE 90187 Umeå.
    Recent Glacier Recession – a New Source of Postglacial Treeline and Climate History in the Swedish Scandes2012In: Landscape Online, ISSN 1865-1542, E-ISSN 1865-1542, Vol. 26, p. 1-38Article in journal (Refereed)
    Abstract [en]

    Climate warming during the past century has imposed recession of glaciers and perennial snow/ice patches along the entire Swedish Scandes. On the newly exposed forefields, subfossil wood remnants are being outwashed from beneath ice and snow bodies. In Scandinavia, this kind of detrital wood is a previously unused source of postglacial vegetation and climate history. The present study reports radiocarbon dates of a set of 78 wood samples, retrieved from three main sites, high above modern treelines and stretching along the Swedish Scandes. In accord with previous studies, pine (Pinus sylvestris) colonized early emerging nunataks already during the Late Glacial. Around 9600-9500 cal. yr BP a first massive wave of tree establishment, birch and pine, took place in "empty" glacier cirques. Both species grew 400-600 m above their present-ay treeline position and the summer temperatures may have been 3.5 °C warmer than present. In respons to Neoglacial cooling, treelines of both birch and pine descended until their final disappearance from the record 4400 and 5900 cal. yr BP, respectively. During the entire interval 9600 to 4400 cal. yr BP, birch prospered in a 100-150 broad belt above the uppermost pines. The recent emergence of tree remnants in the current habitats relates to the contemporary episode of climate warming, possibly unprecedented for several past millennia. It is inferred, by an anology with the past, that in a future scenario with summers 3.5 ° warmer than present, the birch treeline may rise by 600 m or so.

  • 116.
    Öhlund, Thomas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Coated Surfaces for Inkjet-Printed Conductors2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, a number of commercially available paper substrates of various types are characterized and their characteristics related to the performance of inkjet-printed conductors using silver nanoparticle ink. The evaluated performance variables are electrical conductivity as well as the minimum achievable conductor width and the edge raggedness. It is shown that quick absorption of the ink carrier is beneficial for achieving well defined conductor geometry and high conductivity. Surface roughness with topography variations of sufficiently large amplitude and frequency is detrimental to print definition and conductivity. Porosity is another important factor, where the characteristic pore size is much more important than the total pore volume. A nearly ideal porous coating has large total pore volume but small characteristic pore size, preferably smaller than individual nanoparticles in the ink. Apparent surface energy is important for non-absorbing substrates but of limited importance for coatings with a high absorption rate.Additionally, a concept for improving the geometric definition of inkjet-printed conductors on nonporous films has been demonstrated. By coating the films with polymer–based coatings to provide a means of ink solvent removal, minimum conductor width were reduced a factor 2 or more.Intimately connected to the end performance of printed conductors is a well adapted sintering methodology. A comparative evaluation of a number of selective sintering methods has been performed on paper substrates with different heat tolerance. Pulsed high-power white light was found to be a good compromise between conductivity performance, reliability and production adaptability.The purpose of the work conducted in this thesis is to increase the knowledge base in how surface characteristics of papers and flexible films affect performance of printed nanoparticle structures. This would improve selection, adaption of, or manufacturing of such substrates to suit printed high conductivity patterns such as printed antennas for packaging.

  • 117.
    Öhlund, Thomas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Andersson, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Effect of Paper Properties on Electrical Conductivity and Pattern Definition for Silver Nanoparticle Inkjet Ink2012In: Proceedings of LOPE-C 2012, 2012, p. 115-119Conference paper (Refereed)
    Abstract [en]

    In this work, electrical conductivity and print pattern definition isstudied for silver nanoparticle ink, printed on ten commerciallyavailable paper substrates. Interrelations and correlations betweenelectrical conductivity, print pattern definition and a set ofmeasured paper properties are analyzed with a multivariatestatistical method. The papers are characterized in terms ofabsorption rate, porosity, apparent surface energy, surfaceroughness and surface material content. The statistical analysisshows that electrical conductivity and print pattern definition arecorrelated. Conductivity and print definition are correlatedpositively with absorption rate and negatively with surfaceroughness. A model based on projection to latent structures (PLS) isbuilt from the measurement data, showing adequate values of modelfit and predictive ability. This suggests that the chosen propertiesand methods for surface characterization are relevant in estimatingoverall performance of inkjet-printed conductors on paper.Additionally, a qualitative examination of the nanoparticle layercharacteristic is conducted with SEM cross section microscopy.Some of the properties and mechanisms of importance to theconductivity of the printed conductors are highlighted, of whichsome are crucial for achieving conductivity. Physical characteristicsof a suitable paper surface should ideally include large absorptioncapability for the ink carrier, but most importantly, a characteristicpore size and surface roughness amplitude that are both smallcompared to the dry ink layer thickness. If these criteria are met,paper media can be a low cost, comparably high performancealternative for metal nanoparticle inks in printed electronics applications.

  • 118.
    Öhlund, Thomas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Örtegren, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Forsberg, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Paper Surfaces for Metal Nanoparticle Inkjet Printing2012In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 259, p. 731-739Article in journal (Refereed)
    Abstract [en]

    The widespread usage of paper and board offer largely unexploited possibilities for printed electronics applications. Reliability and performance of printed devices on comparatively rough and inhomogenous surfaces of paper does however pose challenges.Silver nanoparticle ink has been deposited on ten various paper substrates by inkjet printing. The papers are commercially available, and selected over a range of different types and construction. A smooth nonporous polyimide film was included as a nonporous reference substrate. The substrates have been characterized in terms of porosity, absorption rate, apparent surface energy, surface roughness and material content. The electrical conductivity of the resulting printed films have been measured after drying at 60°C and again after additional sintering at 110°C. A qualitative analysis of the conductivity differences on the different substrates based on surface characterization and SEM examination is presented. Measurable parameters of importance to the final conductivity are pointed out, some of which are crucial to achieve conductivity. When certain criteria of the surfaces are met, paper media can be used as low cost, but comparably high performance substrates for metal nanoparticle inks in printed electronics applications.

  • 119.
    Örtegren, Jonas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Alfthan, Elisabeth
    Hägglund, Jan-Erik
    Paper for high speed inkjet: a study on dimensional stability and print quality2012In: Conference proceedings International Paper Physics Conference, Innventia AB, 2012, p. 129-130Conference paper (Other academic)
    Abstract [en]

    Inkjet printing technology has developed in recent years, and inkjet machines for print production are now on the market. Inkjet printing at high speed puts new demands on the paper. In this work, pilot papers with known content were produced in a pilot paper machine. Inkjet printing was carried out with waterbased inkjet ink and dimensional stability and print quality were evaluated.

  • 120.
    Örtegren, Jonas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Öhlund, Thomas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Niga, Petru
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Makeen, Khalid
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Print quality issues concerning inkjet printing of colour and electronics on paper2012In: PTS Symposium: Paper and Imaging 2012, Munich, Germany, 2012, p. 251-263Conference paper (Other academic)
    Abstract [en]

    The market value of the digital printing technologies electrophotography and inkjet is expected to grow during this decade. The introduction of multicolour high speed inkjet machines in recent years has again turned print quality into an important issue. In addition, the combination of digital printing and traditional printing technologies for variable data print production requires paper and ink which gives good and comparable print quality using different printing technologies. Printed electronics, most commonly utilizing the printing technologies screen, gravure, flexography or inkjet, is forecasted a bright future. The interest in paper as print media for printed electronics and flexible electronics has recently increased, mainly due to the widespread usage of paper, the low cost of paper, and due to the fact that paper is produced mainly from natural renewable resources. The requirements on the print concern here not primarily the visual impression, but rather the functionality, for example the conductivity of printed tracks.

    We have studied the effect of surface treatment of paper on inkjet print quality; we have looked more closely at the effect of different paper surface parameters, and shown that these parameters can have a large impact on both chroma and detail reproduction when printing with pigmented inkjet inks. Combination of inkjet with traditional printing technologies can give good print quality when carefully combining printing technology, ink and print media. Moreover, some knowledge concerning printing of colour may be transferred to the field of printed electronics, although the prerequisites on the print products are quite different. We have studied how the surface properties of coated paper affects the electrical conductivity and the print quality of inkjet printed electronics. In addition, coating of paper surfaces by laboratory methods and evaluation of functionality has been performed. The work is a base for our ongoing research on adding of functionalities to paper and packaging in a flexible and cost efficient way by utilization of printing technologies and novel materials.

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