Vegar Ottesen

• Ravlo, Erlend; Sousa, Mirta; Andresen, Lise Lima; Holberg-Petersen, Mona; Klundby, Ingvild & Aas, Per Arne [Show all 14 contributors for this article] (2023). A fast, low-cost, robust and high-throughput method for viral nucleic acid isolation based on NAxtra magnetic nanoparticles. Scientific Reports. 13(1), p. 1–7. doi: 10.1038/s41598-023-38743-0. Full text in Research Archive Show summary

  The year of 2020 was profoundly marked by a global pandemic caused by a strain of coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiological agent of coronavirus disease 2019 (COVID-19). To control disease spread, a key strategy adopted by many countries was the regular testing of individuals for infection. This led to the rapid development of diagnostic testing technologies. In Norway, within a week, our group developed a test kit to quickly isolate viral RNA and safely detect SARS-CoV-2 infection with sensitivity comparable to available kits. Herein, the procedure employed for the detection of SARS-CoV-2 in swab samples from patients using the NTNU-COVID-19 test kit is described in detail. This procedure, based on NAxtra magnetic nanoparticles and an optimized nucleic acid extraction procedure, is robust, reliable, and straightforward, providing high-quality nucleic acids within 14 min. The NAxtra protocol is adaptable and was further validated for extraction of DNA and RNA from other types of viruses. A comparison of the protocol on different liquid handling systems is also presented. Due to the simplicity and low cost of this method, implementation of this technology to diagnose virus infections on a clinical setting would benefit health care systems, promoting sustainability.

• Torstensen, Jonathan Økland; Ottesen, Vegar; Rodríguez-Fabià, Sandra; Syverud, Kristin; Johansson, Lars & Lervik, Anders (2022). The influence of temperature on cellulose swelling at constant water density. Scientific Reports. 12(1). doi: 10.1038/s41598-022-22092-5. Full text in Research Archive Show summary

  We have in this paper investigated how water sorbs to cellulose. We found that both cellulose nanofibril (CNF) and cellulose nanocrystal (CNC) films swell similarly, as they are both mainly composed of cellulose. CNF/CNC films subjected to water at 0.018 kg/m3 at 25 °C and 39 °C, showed a decrease in swelling from ~ 8 to 2%. This deswelling increased the tensile index of CNF-films by ~ 13%. By molecular modeling of fibril swelling, we found that water sorbed to cellulose exhibits a decreased diffusion constant compared to bulk water. We quantified this change and showed that diffusion of sorbed water displays less dependency on swelling temperature compared to bulk water diffusion. To our knowledge, this has not previously been demonstrated by molecular modeling. The difference between bulk water diffusion (DWW) and diffusion of water sorbed to cellulose (DCC) increased from DWW − DCC ~ 3 × 10–5 cm/s2 at 25 °C to DWW − DCC ~ 8.3 × 10–5 cm/s2 at 100 °C. Moreover, water molecules spent less successive time sorbed to a fibril at higher temperatures.

• Joseph, Prajin; Ottesen, Vegar; Tanase-Opedal, Mihaela & Moe, Størker T. (2022). Morphology of lignin structures on fiber surfaces after organosolv pretreatment. Biopolymers. ISSN 0006-3525. 113(9). doi: 10.1002/bip.23520. Full text in Research Archive Show summary

  The redeposition of lignin to the fiber surface after organosolv pretreatment was studied using two different reactor types. Results from the conventional autoclave reactor suggest that redeposition occurs during the cooling down stage. Redeposited particles appeared to be spherical in shape. The size and population density of the particles depends on the concentration of organosolv lignin in the cooking liquor, which is consistent with the hypothesis that reprecipitation of lignin occurs when the system is cooled down. The use of a displacement reactor showed that displacing the spent cooking liquor with fresh cooking liquor helps in reducing the redeposition and the inclusion of a washing stage with fresh cooking liquor reduced the reprecipitation of lignin, particularly on the outer fiber surfaces. Redeposition of lignin was still observed on regions that were less accessible to washing liquid, such as fiber lumens, suggesting that complete prevention of redeposition was not achieved.

• Ottesen, Vegar & Syverud, Kristin (2020). Swelling of individual cellulose nanofibrils in water, role of crystallinity: an AFM study. Cellulose. ISSN 0969-0239. 28, p. 1–11. doi: 10.1007/s10570-020-03517-8. Full text in Research Archive Show summary

  Atomic force microscopy (AFM) can be used to quantitatively study nanomaterials in different media, e.g. vacuum, air, or submerged in a liquid. A technique was developed to study swelling of individual cellulose nanofibrils (CNFs) using AFM. As a case study, CNFs with different degrees of crystallinity (DoC) were examined for swellability going from dry to wet (submerged in de-ionized water). Swelling was found to depend on DoC, but no significant correlation between fibril diameter and swellability was seen. Upon introduction of de-ionized water high DoC samples (65±2%) were found to have a diameter increase of 34% on average, whereas low DoC (44±2%) were found to have a diameter increase of 44% on average. A tested control, consisting of platinum nanowires on silisium, did not swell.

• Bhujbal, Swapnil Vilas; Dekov, Maren; Ottesen, Vegar; Dunker, Karen; Lale, Rahmi & Sletmoen, Marit (2020). Effect of design geometry, exposure energy, cytophilic molecules, cell type and load in fabrication of single-cell arrays using micro-contact printing. Scientific Reports. 10. doi: 10.1038/s41598-020-72080-w. Full text in Research Archive Show summary

  In this study a range of factors influencing the fabrication of single-cell arrays (SCAs) are identified and investigated. Micro-contact printing was used to introduce spots coated with polyethyleneimine or Matrigel on glass surfaces pre-coated with polyethylene glycol. Unmodified E. coli, Synechococcus sp., Chlamydomonas reinhardtii as well as diverse mammalian cells including HUVEC, AAV293, U87, OHS, PC3, SW480, HepG2 and AY-27 were successfully immobilised onto the chemically coated spots. The developed SCAs show high cell viability and probability for capturing single-cells. A discrepancy between the size and shape of the squares described in the design file and the actual structures obtained in the final PDMS structure is characterised and quantified. The discrepancy is found to be depending on the exposure energy used in the photolithography process as well as the size of the squares and their separation distance as detailed in the design file. In addition to these factors, the effect of the cell density loaded onto the patterned surfaces is also characterised. The systematic characterisation of key parameters that need to be optimised prior to the fabrication of SCAs is essential in order to increase the efficiency and reproducibility of future fabrication of SCAs for single-cell studies.

• Dai, Zhongde; Ottesen, Vegar; Deng, Jing; Helberg, Ragne M Lilleby & Deng, Liyuan (2019). A Brief Review of Nanocellulose Based Hybrid Membranes for CO2 Separation. Fibers. 7:40(5), p. 1–18. doi: 10.3390/FIB7050040. Full text in Research Archive Show summary

  Due to the high specific surface area, high mechanical strength and broad possibility of surface modification, nanocellulose has obtained much attention as a new class of bio-based nanomaterials with promising potential in a wide variety of applications. Recently, a considerable amount of research has been aimed to the fabrication of nanocellulose based hybrid membranes for water treatment. However, nanocellulose based hybrid gas separation membrane is still a new research area. Herein, we force on recent advancements in the fabrication methods and separation performances of nanocellulose-based hybrid membranes for CO2 separation, the transport mechanisms involved, along with the challenges in the utilization of nanocellulose in membranes. Finally, some perspectives on future R&D of nanocellulose-based membranes for CO2 separation are proposed.

• Ottesen, Vegar; Larsson, Per Tomas; Chinga-Carrasco, Gary; Syverud, Kristin & Gregersen, Øyvind Weiby (2019). Mechanical properties of cellulose nanofibril films: effects of crystallinity and its modification by treatment with liquid anhydrous ammonia. Cellulose. ISSN 0969-0239. 26(11), p. 6615–6627. doi: 10.1007/s10570-019-02546-2. Full text in Research Archive Show summary

  The influence of cellulose crystallinity on mechanical properties of cellulose nano-fibrils (CNF) was investigated. Degree of crystallinity (DoC) was modified using liquid anhydrous ammonia. Such treatment changes crystal allomorph from cellulose I to cellulose III, a change which was reversed by subsequent boiling in water. DoC was measured using solid state nuclear magnetic resonance (NMR). Crystalline index (CI) was also measured using wide angle x-ray scattering (WAXS). Cotton linters were used as the raw material. The cotton linter was ammonia treated prior to fibrillation. Reduced DoC is seen to associate with an increased yield point and decreased Young modulus. Young modulus is here defined as the maximal slope of the stress-strain curves. The association between DoC and Young modulus or DoC and yield point are both statistically significant. We cannot conclude there has been an effect on strainability. While mechanical properties were affected, we found no indication that ammonia treatment affected degree of fibrillation. CNF was also studied in air and liquid using atomic force microscopy (AFM). Swelling of the nanofibers was observed, with a mean diameter increase of 48.9 %

• Ottesen, Vegar; Kumar, Vinay; Toivakka, Martti; Chinga-Carrasco, Gary; Syverud, Kristin & Gregersen, Øyvind Weiby (2017). Viability and properties of roll-to-roll coating of cellulose nanofibrils on recycled paperboard. Nordic Pulp & Paper Research Journal (NPPRJ). ISSN 0283-2631. 32(2), p. 179–188. doi: 10.3183/NPPRJ-2017-32-02-p179-188. Full text in Research Archive Show summary

  Cellulose nanofibrils (CNF) are, due in large part to excellent gas barrier properties, a potential environmentally friendly alternative to inorganic and petrochemical coatings of e.g. paperboard in packaging applications. In the current paper successful roll-to-roll coating of three qualities of CNF is demonstrated on a recycled quality, porous paperboard using a custom-built pilot machine. Single layers of three different thicknesses were applied for each coating. The three CNF qualities used were carboxymethylated CNF (CNF-C), TEMPO- oxidized CNF (CNF-T) and mechanically produced CNF without chemical pre-treatment (CNF-M). All three qualities, which have a range of surface charge, fibril size and fibril size distribution, are shown to produce films that adhere well to the base board. It is revealed that the coating is suspended across surface pores in the base board, as opposed to penetrate into the base board pore structure. Samples were investigated for air and water permeability, gloss, surface roughness and hole density in the coating. Chemically pretreated qualities outperform CNF-M. Addition of 5 wt% carboxy-methyl cellulose (CMC) was shown to reduce hole formation, improve gloss and reduce surface roughness. For thick applications of pre-treated CNF, in particular CNF-C, mechanical strength of the board in and out of the plane increase beyond the un-treated or water treated base board. Possibly a consequence of matter migrating through the base board from the CNF suspension.

• Kumar, Vinay; Ottesen, Vegar; Syverud, Kristin; Gregersen, Øyvind Weiby & Toivakka, Martti (2017). Coatability of cellulose nanofibril suspensions: Role of rheology and water retention. BioResources. 12(4), p. 7656–7679. doi: 10.15376/biores.12.4.7656-7679. Full text in Research Archive Show summary

  Cellulose nanofibril (CNF) suspensions are not easily coatable because of their excessively high viscosity and yield stress, even at low solids concentrations. In addition, CNF suspensions vary widely in their properties depending on the production process used, which can affect their processability. This work reports roll-to-roll coating of three different types of CNF suspensions with a slot-die, and the influence of rheology and water retention on coatability is addressed. The impact of CMC addition on the high and low shear rate rheology, water retention, coatability, and final coating quality of these suspensions is reported. All three CNF suspensions were coated successfully using the slot-die coating process. CMC addition further improved the coatability by positively influencing both the low and high shear rate viscosity and water retention of the CNF suspensions. All CNF coatings significantly improved the air, heptane vapor, grease and oil barrier, while reducing the water vapor transmission rate to some extent.

• Ottesen, Vegar; Syverud, Kristin & Gregersen, Øyvind Weiby (2016). Mixing of cellulose nanofibrils and individual furnish components: Effects on paper properties and structure. Nordic Pulp & Paper Research Journal (NPPRJ). ISSN 0283-2631. 31(3), p. 441–447. doi: 10.3183/NPPRJ-2016-31-03-p441-447. Full text in Research Archive Show summary

  Thermo-mechanical pulp (TMP) handsheets with different fractions of cellulose nano fibrils (CNF) and ground calcium carbonate (GCC) were made. CNF and retention chemicals were added in three different ways; to GCC, to long fibre fraction (LFF) or to complete furnish. The different addition strategies affected dewatering time, tensile strength and permeability, however opacity was not affected. Depending on filler and CNF levels, adding CNF to GCC produced the most beneficial effects on paper properties; CNF had a lower impact on dewatering times and permeability and GCC reduced strength less than for competing strategies. Adding CNF to LFF produced the least beneficial results using the same metrics. Scanning electron microscopy (SEM) analysis of the sheets reveal that sheets produced using the different strategies are structurally different; adding CNF and retention chemicals to GCC appears to have increased GCC clustering, whereas adding CNF and retention chemicals to LFF appears to have increased the fraction of GCC adsorbed on the fiber walls. CNF and retention chemical addition to complete furnish showed GCC clustering and adhering to the fiber walls, of which clustering appeared the most common.

• Arnfinnsdottir, Nina Bjørk; Ottesen, Vegar; Lale, Rahmi & Sletmoen, Marit (2015). The Design of Simple Bacterial Microarrays: Development towards Immobilizing Single Living Bacteria on Predefined Micro-Sized Spots on Patterned Surfaces. PLOS ONE. 10(6). doi: 10.1371/journal.pone.0128162. Full text in Research Archive Show summary

  In this paper we demonstrate a procedure for preparing bacterial arrays that is fast, easy, and applicable in a standard molecular biology laboratory. Microcontact printing is used to deposit chemicals promoting bacterial adherence in predefined positions on glass surfaces coated with polymers known for their resistance to bacterial adhesion. Highly ordered arrays of immobilized bacteria were obtained using microcontact printed islands of polydopamine (PD) on glass surfaces coated with the antiadhesive polymer polyethylene glycol (PEG). On such PEG-coated glass surfaces, bacteria were attached to 97 to 100% of the PD islands, 21 to 62% of which were occupied by a single bacterium. A viability test revealed that 99% of the bacteria were alive following immobilization onto patterned surfaces. Time series imaging of bacteria on such arrays revealed that the attached bacteria both divided and expressed green fluorescent protein, both of which indicates that this method of patterning of bacteria is a suitable method for single-cell analysis.

View all works in NVA

• Ali, Zeeshan; Ravlo, Erlend; Aas, Per Arne; Hagen, Lars; Erlandsen, Sten Even & Ottesen, Vegar [Show all 9 contributors for this article] (2022). Scalable Production of Silica-coated Magnetic Nanobeads and their Applications in Viral Diagnostics. Full text in Research Archive
• Ottesen, Vegar (2021). Nanomaterials Characterization by Electron Microscopy. Full text in Research Archive
• Ottesen, Vegar (2021). Aftenposten Forklart Junior. Kan man slutte å bruke plast? [Internet]. https://www.aftenposten.no/podkast/ap/program/100195. Full text in Research Archive
• Ottesen, Vegar (2021). Superrask forskning - Synergi og samarbeid. Full text in Research Archive
• Ottesen, Vegar (2021). Super nanoteknologi fra naturen. Full text in Research Archive
• Ottesen, Vegar (2021). Nanomaterials Characterization by Atomic Force Microscopy. Full text in Research Archive
• Joseph, Prajin; Ottesen, Vegar; Opedal, Mihaela Tanase & Moe, Størker T. (2021). Organosolv Pretreatment of Nordic Spruce for Biorefinery applications. Full text in Research Archive
• Ottesen, Vegar (2021). Super nanoteknologi fra naturen. Full text in Research Archive
• Ottesen, Vegar (2021). Forsker på skjerm, Ole Vig videregående skole. Full text in Research Archive
• Ottesen, Vegar (2021). Super nanoteknologi fra naturen. Full text in Research Archive
• Ottesen, Vegar (2021). Hva er et virus? Full text in Research Archive
• Ottesen, Vegar (2021). NTNUs koronatest: Utvikling og anvendelse. Full text in Research Archive Show summary

  Foredrag om utvikling av og potensialet til NTNUs korona-tester, etablering av LyBe Scientific og fremtidig horisont for testen.

• Ottesen, Vegar (2020). Nanotechnology - an Introduction. Full text in Research Archive
• Ottesen, Vegar (2020). Polymeric and biopolymeric nanomaterials - an overview. Full text in Research Archive
• Ottesen, Vegar; Larsson, Per Tomas & Syverud, Kristin (2019). AFM study cellulose nano-fibril swelling in water - Relevance of nanofiber crystallinity. Full text in Research Archive
• Ottesen, Vegar (2019). Inn med Planten ut med Plasten. Full text in Research Archive
• Ottesen, Vegar (2019). Plast og nano fra naturen. Full text in Research Archive
• Ottesen, Vegar (2019). Nanocellulose og Plast. Full text in Research Archive
• Ottesen, Vegar (2019). Ut med plasten, inn med planten. Full text in Research Archive
• Ottesen, Vegar (2019). Kjemisk prosessteknologi – for fremtidens miljø og klima. Full text in Research Archive
• Ottesen, Vegar & Thomassen, Ellen Befring (2019). Har NTNU-forsker svar på plastproblemet? [Radio]. NRK P3. Full text in Research Archive
• Ottesen, Vegar (2019). Inn med planten - ut med plasten. Full text in Research Archive
• Ottesen, Vegar (2019). PhD Grand Prix 2019 (Konferansier). Full text in Research Archive
• Ottesen, Vegar; Larsson, Per Tomas & Syverud, Kristin (2019). Swelling of Individual Cellulose Nano-Fibrils: Does Crystallinity affect Swellability? Full text in Research Archive
• Ottesen, Vegar (2018). Nano? Inn! Plast? Ut! Full text in Research Archive
• Ottesen, Vegar (2018). Inn med planten - ut med plasten. Full text in Research Archive
• Ottesen, Vegar (2018). Nanocellulose: Tomorrow’s packaging? Full text in Research Archive
• Ottesen, Vegar (2018). Sparebank1 - Idekonkurranse Plast. [Internet]. Facebook. Full text in Research Archive
• Ottesen, Vegar (2018). nanocellulose som et alternativ til plast. Full text in Research Archive
• Ottesen, Vegar (2018). Inn med planten – ut med plasten! Full text in Research Archive
• Ottesen, Vegar; Larsson, Per Tomas; Chinga-Carrasco, Gary; Syverud, Kristin & Gregersen, Øyvind Weiby (2018). CNF Films: Crystallinity and Ductility. Full text in Research Archive
• Ottesen, Vegar; Haugen, Randi Wenche & Brattebø, Helge (2018). Hva kan erstatte plast? [TV]. NTNU Kveld. Full text in Research Archive
• Ottesen, Vegar (2017). Nanocellulose: Plastics Replacer? Full text in Research Archive
• Ottesen, Vegar (2017). Nanocellulose: It's a Wrap! Full text in Research Archive
• Ottesen, Vegar; Syverud, Kristin & Gregersen, Øyvind Weiby (2017). Nanocellulose - et steg nærmere fremtidens innpakking. Kjemi. ISSN 0023-1983. 4. Full text in Research Archive Show summary

  PLAST som materiale dominerer vår hverdag. Vi finner det i alt fra våre klær, via bygg og transportmidler, til kosmetikk og matinnpakking. Plast har blitt et miljøproblem, men vi er avhengige av produkter som nesten utelukkende er laget av plast – fornybare alternativ kan være nesten umulige å finne. Oljebaserte plastprodukter er altså et betydelig, og voksende, problem. Alternativer trengs, og i enkelte sammenhenger kan potensielle alternativer isoleres fra plantematerialer; nanocellulose er en mulig erstatning for plast og aluminiumslag i flere matinnpakkingsprodukter, som væskekartong. Sammen har en gruppe forskere fra Åbo Akdemi i Finland samt RiSE PFI og NTNU i Trondheim nylig publisert arbeid som demonstrerer en skalerbar teknikk for å legge tynne og hele nanocelluloselag på for eksempel papp. Altså et steg i retning realisering av potensielle alternativ til plast i matinnpakking. Materialets opprinnelsessted? De norske skoger.

• Ottesen, Vegar & Opheim, Aagot (2017). Erstatter plast med planter. [Journal]. Adresseavisen. Full text in Research Archive
• Syverud, Kristin & Ottesen, Vegar (2017). Prosjekt plast. Full text in Research Archive
• Ottesen, Vegar; Roede, Erik Dobloug; Syverud, Kristin & Gregersen, Øyvind Weiby (2017). Focused Ion Beam Tomography as a Means for Characterization of CNF in a Paper Matrix. Full text in Research Archive Show summary

  A method to study Cellulose Nanofibril (CNF) distribution in three dimensions within a paper matrix in-situ was developed. Focused Ion Beam (FIB)/Scanning Electron Microscopy (SEM) tomography was used to investigate the distribution of cellulose nanofibers in three dimensions within a paper structure. Sufficient resolution and material contrast was obtained using both secondary and back-scattered electrons in volumes as large as 10^3 μm^3. Challenges and approaches to achieve this are discussed, both with respect to the microscopy technique and with respect to image processing and volume reconstruction. A range of recorded images and reconstructed 3D volumes show the technique capable of resolving CNF in a paper matrix. Results presented show CNF within the paper matrix forming capsules enclosing filler particles. These capsules are seen to only infrequently be in physical contact with the enclosed particles. Similar separation between CNF and enclosed filler particles was tested and confirmed in CNF films with 10 wt% added ground calcium carbonate.

• Ottesen, Vegar (2017). PhD Grand Prix 2017 - populærvitenskapelig foredrag på 5 minutter VInnerforedrag. Full text in Research Archive
• Ottesen, Vegar (2017). Studio 2 «Vi er Plast Entusiaster!». [Radio]. https://radio.nrk.no/serie/studio-2-p2/MKRV20000317/15-03-20. Full text in Research Archive Show summary

  Interviewed about cellulose nanofibrils as an alternative to plastic materials.

• Ottesen, Vegar; Kumar, Vinay; Toivakka, Martti; Chinga-Carrasco, Gary; Syverud, Kristin & Gregersen, Øyvind Weiby (2016). CNF i papir - Rull-til-rull bestrykning. Full text in Research Archive
• Ottesen, Vegar; Syverud, Kristin & Gregersen, Øyvind Weiby (2016). Effects of Cellulose Nanofibril Premixing Strategies for Paper Making. Full text in Research Archive Show summary

  Effects on paper strength, air permeability and filler distribution from CNF premixing with different paper components have been investigated. As a paper additive Cellulose Nano-fibers (CNF) could improve paper strength, permitting the use of more filler or recycled pulp, thereby cutting costs, while retaining paper strength. Various CNF addition strategies may be pursued, it may be added to the complete furnish, it may be pre-flocculated or added to a specific fraction such as the filler or the long fiber fraction. In the event that CNF is pre-mixed with a specific fraction along with retention chemicals it is expected to coat the surface of said fraction, affecting properties like specific surface area (SSA) and surface chemistry of the fraction in question. This, in turn, can be expected to affect the properties of the fraction and subsequently the properties of the resulting paper. While several of the aforementioned strategies can be seen alluded to in patent literature or explored to some degree in scientific literature a comparison or a study of differences is to our knowledge not published. Aiming to address this we have investigated three different addition strategies, premixing mechanically produced CNF with complete furnish, the filler fraction and the long fiber fraction we have found various differences between papers using the different strategies. Structural differences between the strategies are observable with electron microscopy. Tensile strength properties and air permeability also appear affected by the chosen premixing strategy. Results will be presented at TAPPI NANO 2016

• Ottesen, Vegar; Syverud, Kristin & Gregersen, Øyvind Weiby (2016). Bør nanocellulose bindes til en bestemt komponent I furnish? Full text in Research Archive
• Ottesen, Vegar; Syverud, Kristin & Gregersen, Øyvind Weiby (2016). Effects of Premixing CNF with Specific Furnish Components. Full text in Research Archive
• Ottesen, Vegar; Roede, Erik Dobloug; Syverud, Kristin & Gregersen, Øyvind Weiby (2016). Focused Ion Beam Tomography in the 3D Study of Nanocellulose in Paper. Full text in Research Archive
• Hjorth, Ida; Ottesen, Vegar; Svardal, Lisa Gregusson; Kjærvik, Marit; Bazilchuk, Molly Strimbeck & Schlanbusch, Reidun Dahl [Show all 7 contributors for this article] (2015). En Nanohverdag på Fremmarsj». Teknisk Ukeblad. ISSN 0040-2354. Full text in Research Archive
• Ottesen, Vegar; Patil, Nilesh; Breiby, Dag Werner; Syverud, Kristin & Gregersen, Øyvind Weiby (2015). Investigations of Cellulose Nano-Fibrils Produced by Homogenization of Pulp Converted to Cellulose III from Cellulose Iβ by Treatment with Liquid Ammonia. Full text in Research Archive
• Ottesen, Vegar; Syverud, Kristin & Gregersen, Øyvind Weiby (2015). Nanocellulose in Paper and Packaging -Interaction Effects. Full text in Research Archive
• Arnfinnsdottir, Nina Bjørk; Ottesen, Vegar; Lale, Rahmi & Sletmoen, Marit (2014). Bacterial microarrays obtained by spontaneous adhesion of single bacteria on predefined spots on chemically patterned surfaces. Full text in Research Archive
• Ottesen, Vegar; Syverud, Kristin & Gregersen, Øyvind Weiby (2014). Nanocellulose Properties of Interest for Paper and Packaging. Full text in Research Archive Show summary

  Cellulose Nano-Fibrils (CNF) is a biocompatible nano-material with appealing mechanical and optical properties. The high specific surface area (SSA) of nanofibrils ensure that a large fraction of the polymer chains in each fibril are surface fibrils, meaning numerous surface hydroxyl groups will be available to form bonds between components in the paper, ensuring high density and strength. CNF may be added to conventional paper as a strengthening agent. CNF films may be used as a barrier coating , or CNF sheets may be used in a number of products due to their potential transparency, strength and barrier properties. As a paper additive, CNF as a nanomaterial acts as a material that increase density and form bonds between fibers in the paper, providing a increased strength and stiffness whereas dusting and permeability is reduced.For papers where strength is chiefly limited by inter-fiber bonding strength, increases in excess of 100 % may be achieved by addition of small amounts of CNF. Less, but still significant contributions can be seen for papers whose strength is less dependent on inter-fiber bonding strength. Due to the pore-blocking properties of CNF coupled with Cellulose’s hydrophilic properties, dewatering on the paper machine is a challenge when CNF is used in this fashion. The high density, viz. the low porosity and small pore size (~0.47 nm), of CNF films provide a significant reduction in mass-transport. Applying such a film to a less efficient barrier material, or producing a pure CNF film presents oxygen transfer rates comparable with the best synthetic polymer films produced for this purpose3. Sheets of pure CNF or a CNF composite may transmit over 90 % of incident light with a wavelength of 600 nm. This transparency is due to the high density and small fibril size in sheets of pure CNF or a CNF-based composite, which results in a lower scattering coefficient compared to corresponding conventional fiber based sheets. Transparent sheets such as these may be of interest in packaging applications where the packaged goods, such as foodstuffs or luxury articles, is desired displayed to the end customer. The properties of CNF, whether as a film, a paper additive or a major paper or composite component may be of significant industrial interest due to the unique properties of the material. Acknowledgement: The work is done through NORCEL: The Norwegian Nanocellulose Technology Platform, see www.pfi.no, funded by the Research Council of Norway.

• Ottesen, Vegar (2014). Naturen kan gi oss svar. Aftenposten Viten. ISSN 2464-3033. Full text in Research Archive Show summary

  Bakterier og andre mikrober danner lett biofilmer på overflater de kommer i kontakt med. En biofilm er et belegg av bakterier eller mikrober, og utvikles på grunn av et samspill mellom overflaten og mikro-organismene.Innimellom er det ønskelig å holde noe klinisk fritt for bakterier eller i det minste minimere deres tilstedeværelse. I en operasjonssal er pasientens liv avhengig av sterilt utstyr og i slakterier, restauranter og annen matindustri er kundens trygghet avhengig av at maten tilberedes på trygt og relativt bakteriefritt miljø.

• Ottesen, Vegar; Gregersen, Øyvind Weiby & Syverud, Kristin (2018). Cellulose Nanofibrils as Paper Additive and Coating Material: Properties, Distribution and Interaction Effects. Norges teknisk-naturvitenskapelige universitet. ISSN 9788232630219. Full text in Research Archive Show summary

  Cellulose is well-known as the most common bio-polymer on earth. In the cell wall of most plants, it is organized in nanoscopic structures with interesting properties for a wide range of applications, among them as an additive to paper and board - or as an applied coating. One socioeconomic perspective on these applications of the nanomaterial is associated environmental benefits; cellulose nanofibrils (CNF) as an additive to paper and board can improve tensile properties, enabling not just higher filler levels, but also increased potential fraction of recycled fibers in the product. As a coating, given its excellent oxygen barrier properties, CNF also has potential as a replacement for plastics in certain food packaging applications or, conceivably, aluminum in liquid packaging board. In the current work, we have addressed several questions pertaining to these potential applications and some fundamental questions of interest regarding the properties of CNF as individual fibrils and as fibril aggregates. Central questions in this current work, and brief answers later expounded upon, are; • Do fibril properties like crystallinity affect CNF film ductility? – Reducing crystallinity index (CI) is shown to correlate with an increased yield point and decreased Young’s modulus. • How does CNF behave within the paper or board matrix? – CNF appears to coat the surface of the furnish fraction with which it was added or premixed. – When filler particles are encased in CNF, it appears to form hollow capsules encasing the particles, and not - as one would expect - adhere very tightly. • Can CNF be successfully traced and studied within a paper matrix? – Using high resolution FIB/SEM, this has been demonstrated. – Attained resolution: 13×16×15 nm using back-scattered electron (BSE) and 7×9×15 nm for secondary electron (SE). • Are there benefits associated with premixing CNF with different furnish components? – Some benefit can be seen from premixing CNF with the filler fraction. – The effect depends on filler levels and weight fraction of added CNF. • Can CNF be applied as a barrier coating in a roll-to-roll scenario? – Highly fibrillated CNF, oxidized or not, can be used in a roll-to-roll coating situation. – Rheology plays a role in quality of applied coatings. – The mode of adhesion to the base board appears to be exclusively Physico-chemical, not mechanical. The above list gives an overview, a somewhat more expansive summary follows. Fundamentals: Crystallinity. By treatment with liquid anhydrous ammonia CI of cotton linter was reduced prior to homogenization and fibrillation. Films cast from the resulting CNF suspensions were shown to have a lower Young’s modulus and higher yield point, although crystallinity did not appear to have a significant effect on strain at break. Films of CNF treated with liquid ammonia in the same way shrank, cockled, lost mass and showed a strong increase in strain at break in addition to reduced Young’s modulus and increased yield point. Films treated with ammonia saw very large changes in mechanical properties. We conclude this is due to the cockling and shrinkage of the film itself, and not due to changes in crystallinity. Fundamentals: CNF in a paper matrix. FIB/SEM dual beam system was employed to perform investigations of CNF distribution within the paper matrix. We found the attainable resolution appears adequate to qualitatively trace CNF in volumes as large as 103 μm3 using SE. While BSE delivers reduced contrast and resolution, reduced artefacts due to surface unevenness and other effects made quantitative analysis more easily achieved using this higher-energy signal. Achieved resolutions were approximately 13×16×15 nm using BSE and 7×9×15 nm for SE. Fundamentals: Swelling of individual fibrils. Using atomic force microscopy (AFM) in liquid media (de-ionized water) and air individual fibrils were imaged in air and, later, water. As the same area was imaged the swelling of individual fibrils could be studied in detail. After 30 minute submersion, a mean swelling of 48.9 % was observed, with a standard deviation of 27.8 %. CNF-Capsule Formation. Super-resolution investigation of paper with added CNF shows the CNF appearing to form hollow capsules around filler particles. We hypothesize this is due in part to non-isometric drying. We believe it is conceivable that the surface of these capsules is drying faster, having a lower moisture content at any given time than its interior, leading to a force balance during drying favoring separation over tight conformation to the encased particle. Further investigation into the formation of such complexes by attempting to reproduce the phenomenon was begun in 2017 and continues into 2018. CNF-Premixing Strategies: Effects. We premixed mechanically produced CNF and retention aid with the long fiber fraction (LFF), the filler fraction or added them straight to (otherwise complete) furnish. We found that for high filler levels and high CNF addition levels there is a beneficial effect to dewatering times and tensile strength. Air permeability was affected similarly to dewatering times. Optical properties were not found to differ between the chosen strategies. Scanning electron microscopy (SEM) investigations of paper surfaces appears to suggest that filler particles adhere to the surface of the fraction to which CNF and retention aids were premixed. CNF as a barrier coating: Roll-to-roll application. Three qualities of CNF, TEMPO-oxidized CNF (CNF-T), carboxymethylated CNF (CNF-C) and mechanically produced CNF (CNF-M), all with and without added carboxymethylcellulose (CMC), were applied as a coating to a rough, recycled quality board. Using a single applied coating, an even, smooth surface was achieved with air resistance correlated with CNF quality, coating thickness and CMC addition. We found that lower fibril diameter correlates with improved coating. For the CNF qualities with lowest mean fibril diameter addition of CMC reduced viscosity, and appears to have created a smoother coat. We showed that SEM can be used to quantitatively investigate coating quality and gain insight into the foundation for observed air resistance values.

• Ottesen, Vegar; Sletmoen, Marit & Arnfinnsdottir, Nina Bjørk (2014). Bacterial Microarrays by Microcontact Printing: Development of a Method for Immobilizing Live Bacteria on Microarrays. Norges teknisk-naturvitenskapelige universitet. Full text in Research Archive Show summary

  Traditional microbiological experimental methods generally reveal population-wide statistics and are not capable of revealing variations between individual cells. In an effort to address this, a cheap, quick and easy means of producing micro-arrays with live bacteria immobilized on the array's coordinates has been developed. To achieve this, microcontact printing (µCP) was used to print circular PD ``islands'' onto a surface coated with either PEG or PVA. The bacteria, Pseudomonas putida KT2440 were successfully immobilized on approximately 97% of the printed islands, depending on island diameter. A LIVE/DEAD® BacLight™ assay revealed that over 99% of the immobilized bacteria survive the immobilization on the array. Qualitative analysis suggests the bacteria survive for hours after immobilization, provided nutrients are available. The developed method may, by revising the stamp design and/or choice of elastomer, likely be optimized to immobilize only one bacterium per array coordinate.

View all works in NVA