Browsing by Author "Rojas Gaona, Orlando"

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  • 3D printing and properties of cellulose nanofibrils-reinforced quince seed mucilage bio-inks
    (2021-12-01) Bani Asadi, Hossein; Teixeira Polez, Roberta; Kimiaei, Erfan; Madani, Zahraalsadat; Rojas Gaona, Orlando; Österberg, Monika; Seppälä, Jukka
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Plant-based hydrogels have attracted great attention in biomedical fields since they are biocompatible and based on natural, sustainable, cost-effective, and widely accessible sources. Here, we introduced new viscoelastic bio-inks composed of quince seed mucilage and cellulose nanofibrils (QSM/CNF) easily extruded into 3D lattice structures through direct ink writing in ambient conditions. The QSM/CNF inks enabled precise control on printing fidelity where CNF endowed objects with shape stability after freeze-drying and with suitable porosity, water uptake capacity, and mechanical strength. The compressive and elastic moduli of samples produced at the highest CNF content were both increased by ~100% (from 5.1 ± 0.2 kPa and 32 ± 1 kPa to 10.7 ± 0.5 and 64 ± 2 kPa, respectively). These values ideally matched those reported for soft tissues; accordingly, the cell compatibility of the printed samples was evaluated against HepG2 cells (human liver cancer). The results confirmed the 3D hydrogels as being non-cytotoxic and suitable to support attachment, survival, and proliferation of the cells. All in all, the newly developed inks allowed sustainable 3D bio-hydrogels fitting the requirements as scaffolds for soft tissue engineering.
  • Ascorbic acid-loaded polyvinyl alcohol/cellulose nanofibril hydrogels as precursors for 3D printed materials
    (2021-11) Bani Asadi, Hossein; Madani, Zahraalsadat; Ajdary, Rubina; Rojas Gaona, Orlando; Seppälä, Jukka
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We proposed a simple method to process hydrogels containing polyvinyl alcohol and cellulose nanofibrils (PVA/CNF) to prepare volumetric architectures by direct ink writing (DIW). The presence of CNF in the aqueous PVA suspensions conferred rheology profiles that were suitable for extrusion and solidification in pre-designed shapes. The viscoelastic behavior of the hybrid inks enabled precise control on processability and shape retention, for instance, as demonstrated in multilayered lattice structures of high fidelity. After lyophilization, the obtained 3D-printed hydrogels presented a very high porosity, with open and interconnected pores, allowing a high-water uptake capacity (up to 1600%). The mechanical strength of the composite 3D-printed materials matched those of soft tissues, opening opportunities for skin applications. As such, drug-loaded samples revealed a controlled and efficient delivery of an antioxidant (ascorbic acid) in PBS buffer media at 23 °C (~80% for 8 h). Altogether, PVA/CNF hydrogels were introduced as suitable precursors of 3D-lattice geometries with excellent physical and mechanical characteristics.
  • Biological activity of multicomponent bio-hydrogels loaded with tragacanth gum
    (2022-08-31) Teixeira Polez, Roberta; Morits, Maria; Jonkergouw, Christopher; Phiri, Josphat; Valle-Delgado, Juan José; Seppälä, Jukka; Linder, Markus B.; Maloney, Thaddeus; Rojas Gaona, Orlando; Österberg, Monika
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Producing hydrogels capable of mimicking the biomechanics of soft tissue remains a challenge. We explore the potential of plant-based hydrogels as polysaccharide tragacanth gum and antioxidant lignin nanoparticles in bioactive multicomponent hydrogels for tissue engineering. These natural components are combined with TEMPO-oxidized cellulose nanofibrils, a material with known shear thinning behavior. Hydrogels presented tragacanth gum (TG) concentration-dependent rheological properties suitable for extrusion 3D printing. TG enhanced the swelling capacity up to 645% and the degradation rate up to 1.3%/day for hydrogels containing 75% of TG. Young's moduli of the hydrogels varied from 5.0 to 11.6 kPa and were comparable to soft tissues like skin and muscle. In vitro cell viability assays revealed that the scaffolds were non-toxic and promoted proliferation of hepatocellular carcinoma HepG2 cells. Therefore, the plant-based hydrogels designed in this work have a significant potential for tissue engineering.
  • Cogrinding Wood Fibers and Tannins: Surfactant Effects on the Interactions and Properties of Functional Films for Sustainable Packaging Materials
    (2020-05-11) L. Missio, André; Dufau Mattos, Bruno; Gomide Otoni, Caio; Gentil, Marina; Coldebella, Rodrigo; Khakalo, Alexey; A. Gatto, Darci; Rojas Gaona, Orlando
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We report on the combination of cellulose nanofibrils (CNFs) and condensed tannins from Acacia mearnsii for the development of hybrid, functional films. The tannins are fractionated and concentrated in polyphenolics that are used for functional components in the hybrid materials. Cogrinding of wood fibers with the tannins in aqueous media allows simultaneous fiber deconstruction and in situ binding of tannins on the freshly exposed cellulosic surfaces. Hence, a tightly bound bicomponent system is produced, which is otherwise not possible if typical adsorption protocols are followed, mainly due to the extensive hydration typical of CNFs. A nonionic surfactant is used to tailor the cellulose-tannin interactions. The proposed strategy not only enables the incorporation of tannins with CNFs but also endows a high and prolonged antioxidant effect of films formed by filtration. Compared to tannin-free films, those carrying tannins are considerably more hydrophobic. In addition, they show selective absorption of ultraviolet light while maintaining optical transparency in the visible range. The proposed simple protocol for incorporating tannins and surfactants with CNFs is suitable to produce functional materials. This is possible by understanding associated interfacial phenomena in the context of sustainable materials within the concept of the circular bioeconomy.
  • Deconstruction and Reassembly of Renewable Polymers and Biocolloids into Next Generation Structured Materials
    (2021-11-24) Tardy, Blaise; Dufau Mattos, Bruno; Gomide Otoni, Caio; Beaumont, Marco; Majoinen, Johanna; Kämäräinen, Tero; Rojas Gaona, Orlando
     A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    This review considers the most recent developments in supramolecular and supraparticle structures obtained from natural, renewable biopolymers as well as their disassembly and reassembly into engineered materials. We introduce the main interactions that control bottom-up synthesis and top-down design at different length scales, highlighting the promise of natural biopolymers and associated building blocks. The latter have become main actors in the recent surge of the scientific and patent literature related to the subject. Such developments make prominent use of multicomponent and hierarchical polymeric assemblies and structures that contain polysaccharides (cellulose, chitin, and others), polyphenols (lignins, tannins), and proteins (soy, whey, silk, and other proteins). We offer a comprehensive discussion about the interactions that exist in their native architectures (including multicomponent and composite forms), the chemical modification of polysaccharides and their deconstruction into high axial aspect nanofibers and nanorods. We reflect on the availability and suitability of the latter types of building blocks to enable superstructures and colloidal associations. As far as processing, we describe the most relevant transitions, from the solution to the gel state and the routes that can be used to arrive to consolidated materials with prescribed properties. We highlight the implementation of supramolecular and superstructures in different technological fields that exploit the synergies exhibited by renewable polymers and biocolloids integrated in structured materials.
  • Direct Ink Writing of Biocompatible Nanocellulose and Chitosan Hydrogels for Implant Mesh Matrices
    (2022-04-13) Ajdary, Rubina; Reyes Torres, Guillermo; Kuula, Jani; Raussi-Lehto, Eija; Mikkola, Tomi S.; Kankuri, Esko; Rojas Gaona, Orlando
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Direct ink writing via single or multihead extrusion is used to synthesize layer-by-layer (LbL) meshes comprising renewable polysaccharides. The best mechanical performance (683 ± 63 MPa modulus and 2.5 ± 0.4 MPa tensile strength) is observed for 3D printed structures with full infill density, given the role of electrostatic complexation between the oppositely charged components (chitosan and cellulose nanofibrils). The LbL structures develop an unexpectedly high wet stability that undergoes gradual weight loss at neutral and slightly acidic pH. The excellent biocompatibility and noncytotoxicity toward human monocyte/macrophages and controllable shrinkage upon solvent exchange make the cellular meshes appropriate for use as biomedical implants.
  • Effect of Anisotropy of Cellulose Nanocrystal Suspensions on Stratification, Domain Structure Formation, and Structural Colors
    (2018-05-12) Klockars, Konrad; Tardy, Blaise; Borghei, Maryam; Tripathi, Anurodh; Garcia Greca, Luiz; Rojas Gaona, Orlando
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Outstanding optical and mechanical properties can be obtained from hierarchical assemblies of nanoparticles. Herein, the formation of helically ordered, chiral nematic films obtained from aqueous suspensions of cellulose nanocrystals (CNCs) were studied as a function of the initial suspension state. Specifically, nanoparticle organization and the structural colors displayed by the resultant dry films were investigated as a function of the anisotropic volume fraction (AVF), which depended on the initial CNC concentration and equilibration time. The development of structural color and the extent of macroscopic stratification were studied by optical and scanning electron microscopy as well as UV–vis spectroscopy. Overall, suspensions above the critical threshold required for formation of liquid crystals resulted in CNC films assembled with longer ranged order, more homogeneous pitches along the cross sections, and narrower specific absorption bands. This effect was more pronounced for the suspensions that were closer to equilibrium prior to drying. Thus, we show that high AVF and more extensive phase separation in CNC suspensions resulted in large, long-range ordered chiral nematic domains in dried films. Additionally, the average CNC aspect ratio and size distribution in the two separated phases were measured and correlated to the formation of structured domains in the dried assemblies.
  • Form-stable phase change materials from mesoporous balsa after selective removal of lignin
    (2020-10-15) Meng, Yang; Majoinen, Johanna; Zhao, Bin; Rojas Gaona, Orlando
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We produce balsa-based structures by selective removal of lignin. The changes that occur in the main components of balsa upon delignification, including tracheids, closed pits and tylosis vessels, allow the development of mesopores and a substantial increase in fluid permeability. Such system is ideally suited as a support of phase change materials, PCM. Vacuum-assisted impregnation with polyethylene glycol (PEG, a PCM), results in a form-stable PCM system (FPCM). The FPCM displays a high encapsulating capacity (83.5%) at temperatures above the melting PEG transition, with a latent heat of 134 J/g and low supercooling (12 °C). The results are rationalized by the affinity between the unidirectional mesoporous structure and the polymer, involving capillary forces and hydrogen bonding. The leakage-proof FPCM outperforms available systems (based on PEG or other PCMs) supported on minerals or other wood species. Compared to the latter group, the results obtained with balsa relate with its morphology and the effect of residual hemicelluloses in hierarchically-aligned cellulose nano- and microfibrils. The FPCMs resist compressive loads and performs stably for at least 200 cycles of heating and cooling. An insignificant loss in latent heat is observed compared to that of pure PEG. The phase transition temperature fluctuation and non-leaking characteristics under load make the balsa-based FPCM a superior alternative for passive heating/cooling, especially for uses at high ambient temperatures. The reversible thermoregulatory capacity, low cost, high efficiency, renewability, and operability of the balsa-supported FPCM, indicate an excellent option for thermal energy storage and conversion devices.
  • Gas evolution in self-extinguishing and insulative nanopolysaccharide-based hybrid foams
    (2024-12-15) Abidnejad, Roozbeh; Robertson, Daria; Khakalo, Alexey; Gholami Haghighi Fard, Morteza; Seppälä, Ari; Pasquier, Eva; Tardy, Blaise; Dufau Mattos, Bruno; Rojas Gaona, Orlando
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Lightweight, energy-efficient materials in building construction typically include polymeric and composite foams. However, these materials pose significant fire hazards due to their high combustibility and toxic gas emissions, including carbon monoxide and hydrogen cyanide. This study delves into the latter aspects by comparing hybrid systems based on nanofiber-reinforced silica-based Pickering foams with a synthetic reference (polyurethane foams). The extent and dynamics of fire retardancy and toxic gas evolution were assessed, and the results revealed the benefits of combining the thermal insulation of silica with the structural strength of biobased nanofibers, the latter of which included anionic and phosphorylated cellulose as well as chitin nanofibers. We demonstrate that the nanofiber-reinforced silica-based Pickering foams are thermal insulative and provide both fire safety and energy efficiency. The results set the basis for the practical design of hybrid foams to advance environmental sustainability goals by reducing energy consumption in built environments.
  • High-resolution 3D printing of xanthan gum/nanocellulose bio-inks
    (2022-06-01) Baniasadi, Hossein; Kimiaei, Erfan; Teixeira Polez, Roberta; Ajdary, Rubina; Rojas Gaona, Orlando; Österberg, Monika; Seppälä, Jukka
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The current study provides a comprehensive rheology study and a survey on direct ink writing of xanthan gum/cellulose nanocrystal (XG/CNC) bio-inks for developing 3D geometries that mimic soft tissue engineering scaffolds' physical and mechanical properties. The presence of CNC was found to be a critical prerequisite for the printability of XG bio-inks; accordingly, the hybrid XG/CNC bio-inks revealed the excellent viscoelastic properties that enabled precise control of hydrogel shaping and printing of lattice structures composed of up to eleven layers with high fidelity and fair resolution without any deformation after printing. The lyophilized 3D scaffolds presented a porous structure with open and interconnected pores and a porosity higher than 70%, vital features for tissue engineering scaffolds. Moreover, they showed a relatively high swelling of approximately 11 g/g, facilitating oxygen and nutrient exchange. Furthermore, the elastic and compressive moduli of the scaffolds that enhanced significantly upon increasing CNC content were in the range of a few kPa, similar to soft tissues. Finally, no significant cell cytotoxicity was observed against human liver cancer cells (HepG2), highlighting the potential of these developed 3D printed scaffolds for soft tissue engineering applications.
  • Impact of incubation conditions and post-treatment on the properties of bacterial cellulose membranes for pressure-driven filtration
    (2021-01-01) Lehtonen, Janika; Chen, Xiao; Beaumont, Marco; Hassinen, Jukka; Orelma, Hannes; Dumée, Ludovic F.; Tardy, Blaise; Rojas Gaona, Orlando
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Bacterial cellulose (BC) has shown potential as a separation material. Herein, the performance of BC in pressure-driven separation is investigated as a function of incubation conditions and post-culture treatment. The pure water flux of never-dried BC (NDBC), was found to be 9 to 16 times higher than that for dried BC (DBC), in a pressure range of 0.25 to 2.5 bar. The difference in pressure response of NDBC and DBC was observed both in cross-flow filtration and capillary flow porometry experiments. DBC and NDBC were permeable to polymers with a hydrodynamic radius of ∼60 nm while protein retention was possible by introducing anionic surface charges on BC. The results of this work are expected to expand the development of BC-based filtration membranes, for instance towards the processing of biological fluids.
  • Inverse Thermoreversible Mechanical Stiffening and Birefringence in a Methylcellulose/Cellulose Nanocrystal Hydrogel
    (2018-07-09) Hynninen, Ville; Hietala, Sami; McKee, Jason R.; Murtomäki, Lasse; Rojas Gaona, Orlando; Ikkala, Olli; Nonappa, Nonappa
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We show that composite hydrogels comprising methyl cellulose (MC) and cellulose nanocrystal (CNC) colloidal rods display a reversible and enhanced rheological storage modulus and optical birefringence upon heating, i.e., inverse thermoreversibility. Dynamic rheology, quantitative polarized optical microscopy, isothermal titration calorimetry (ITC), circular dichroism (CD), and scanning and transmission electron microscopy (SEM and TEM) were used for characterization. The concentration of CNCs in aqueous media was varied up to 3.5 wt % (i.e, keeping the concentration below the critical aq concentration) while maintaining the MC aq concentration at 1.0 wt %. At 20 °C, MC/CNC underwent gelation upon passing the CNC concentration of 1.5 wt %. At this point, the storage modulus (G′) reached a plateau, and the birefringence underwent a stepwise increase, thus suggesting a percolative phenomenon. The storage modulus (G′) of the composite gels was an order of magnitude higher at 60 °C compared to that at 20 °C. ITC results suggested that, at 60 °C, the CNC rods were entropically driven to interact with MC chains, which according to recent studies collapse at this temperature into ring-like, colloidal-scale persistent fibrils with hollow cross-sections. Consequently, the tendency of the MC to form more persistent aggregates promotes the interactions between the CNC chiral aggregates towards enhanced storage modulus and birefringence. At room temperature, ITC shows enthalpic binding between CNCs and MC with the latter comprising aqueous, molecularly dispersed polymer chains that lead to looser and less birefringent material. TEM, SEM, and CD indicate CNC chiral fragments within a MC/CNC composite gel. Thus, MC/CNC hybrid networks offer materials with tunable rheological properties and access to liquid crystalline properties at low CNC concentrations.
  • Lignin beyond the status quo: Recent and emerging composite applications
    (2024-01-21) Fazeli, Mahyar; Mukherjee, Sritama; Baniasadi, Hossein; Abidnejad, Roozbeh; Mujtaba, Muhammad; Lipponen, Juha; Seppälä, Jukka; Rojas Gaona, Orlando
     A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    The demand for biodegradable materials across various industries has recently surged due to environmental concerns and the need for the adoption of renewable materials. In this context, lignin has emerged as a promising alternative, garnering significant attention as a biogenic resource that endows functional properties. This is primarily ascribed to its remarkable origin and structure that explains lignin's capacity to bind other molecules, reinforce composites, act as an antioxidant, and endow antimicrobial effects. This review summarizes recent advances in lignin-based composites, with particular emphasis on innovative methods for modifying lignin into micro and nanostructures and evaluating their functional contribution. Indeed, lignin-based composites can be tailored for superior physicomechanical characteristics, biodegradability, and surface properties, thereby making them suitable for applications beyond typical, for instance, in ecofriendly adhesives and advanced barrier technologies. Herein, we provide a comprehensive overview of the latest progress in the field of lignin utilization in emerging composite materials.
  • Lignin Nano- and Microparticles as Template for Nanostructured Materials: Formation of Hollow Metal-Phenolic Capsules
    (2018) Tardy, Blaise; Richardson, Joseph J.; Guo, Junling; Lehtonen, Janika; Ago, Mariko; Rojas Gaona, Orlando
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Hollow polymeric, submicrometer-scaled capsules show promise in applications ranging from water remediation to drug delivery, and the preferred method for their synthesis includes templating from sacrificial particles. Such particles are typically non-renewable and the process of selective dissolution used to produce the capsules often requires harsh and/or toxic solvents. Thus, there is a critical need to develop inexpensive, sustainable templates that can be dismantled under mild conditions. Lignins have recently been introduced as renewable precursors for the synthesis of solid particles and can favorably substitute solid particles based on petrochemical (such as latex) or mineral (such as silica) precursors. Conveniently, widely available by-product streams of biomass processing can be used for the supramolecular assembly required for lignin particle formation. Herein, we introduce two common lignin sources (kraft and alkali lignins) as renewable and easily degradable particulate templates for the preparation of hollow polymeric capsules. The polymeric nanocoating, or wall of the capsules, was synthesized from renewable tannins, which self-assemble around the lignin particle template in the presence of metal ions, thereby coordinating into metal-phenolic networks (MPNs). The lignin template particles were easily degraded with aqueous or organic solvents under ambient conditions. Thus, the nanocoating assembly and template disassembly processes can be considered to be fully “green”. Finally, the synthesized hollow capsules were successfully utilized for water clean-up through the degradation of an organic dye, exemplifying a cost-effective and facile route for using environmentally friendly nanomaterials for environmental remediation.
  • Lignin nanoparticles as co-stabilizers and modifiers of nanocellulose-based Pickering emulsions and foams
    (2023-09) Agustin, Melissa B.; Nematollahi, Neda; Bhattarai, Mamata; Oliaei, Erfan; Lehtonen, Mari; Rojas Gaona, Orlando; Mikkonen, Kirsi S.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Nanocellulose is very hydrophilic, preventing interactions with the oil phase in Pickering emulsions. This limitation is herein addressed by incorporating lignin nanoparticles (LNPs) as co-stabilizers of nanocellulose-based Pickering emulsions. LNP addition decreases the oil droplet size and slows creaming at pH 5 and 8 and with increasing LNP content. Emulsification at pH 3 and LNP cationization lead to droplet flocculation and rapid creaming. LNP application for emulsification, prior or simultaneously with nanocellulose, favors stability given the improved interactions with the oil phase. The Pickering emulsions can be freeze–dried, enabling the recovery of a solid macroporous foam that can act as adsorbent for pharmaceutical pollutants. Overall, the properties of nanocellulose-based Pickering emulsions and foams can be tailored by LNP addition. This strategy offers a unique, green approach to stabilize biphasic systems using bio-based nanomaterials without tedious and costly modification procedures.
  • Lignin-first integrated hydrothermal treatment (HTT) and synthesis of low-cost biorefinery particles
    (2020-01-21) Vergara Lourencon, Tainise; Garcia Greca, Luiz; Tarasov, Dmitry; Borrega, Marc; Tamminen, Tarja; Rojas Gaona, Orlando; Balakshin, Mikhail
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Hydrothermal treatments (HTT) are used in the biorefineries to effectively valorize carbohydrate fractions and their products. However, lignin is often marginalized as a secondary component. Herein, we propose a new biorefinery approach focused on lignin valorization. We demonstrate that high-value lignins can be extracted using a simple, green, and affordable process consisting of an optimized HTT followed by lignin extraction with aqueous acetone under ambient conditions. Significantly, the chemical structure and molecular mass of the lignin can be tailored by the selection of the process variables while maintaining a high yield, in the range of ∼60-90%. For example, the average molecular mass (Mw) of the isolated lignins is in the range between 2.5 and 5 kDa, while the amount of β-O-4 linkages is 4-28 per 100 Ar. The extracted lignins are further used to generate micro- and nanoparticles by using an aerosol flow system. The introduced lignin profiling affords control of particle properties, including average size and distribution, surface energy, and wettability. Overall, the suggested approach allows customization of lignin products while achieving a 58% reduction in the lignin particles production costs compared to the lowest prime figures reported so far.
  • Mesoporous carbon soft-templated from lignin nanofiber networks: Microphase separation boosts supercapacitance in conductive electrodes
    (2016) Ago, Mariko; Borghei, Maryam; Haataja, Johannes S.; Rojas Gaona, Orlando
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Flexible electrodes with supercapacitance were developed from highly mesoporous carbon fibers synthesized from lignin. Polyvinyl alcohol (PVA) facilitated the electrospinning of aqueous solutions of lignin and was used as a sacrificial polymer. Most importantly, PVA produced phase-separated domains for extreme surface area (>2000 m2 g-1) and mesoporous volume (0.7 cm3 g-1). An optimized sequential thermal treatment that initially included stabilization at 250 °C, allowed the formation of flexible, freestanding carbon networks upon PVA evolution to the gas phase and carbonization of the as-spun lignin-based fibers. Their main morphological and chemical characteristics were assessed by field emission scanning microscopy, transmission electron tomography reconstructions and Raman spectroscopy. The carbon fiber networks were used directly as electrodes with electrochemical double layer capacitance as determined by cyclic voltammetry and galvanostatic charge/discharge methods. Excellent electrochemical performance was demonstrated from the measured high rate capability and long-term cycling stability. The determined specific capacitance (∼205 F g-1 in 0.5 M Na2SO4 electrolyte) is one of the highest recorded for electrodes obtained from biopolymer precursors. Moreover, the electrical conductivity of the carbon fiber network (386 S m-1) was significantly higher, by two-orders of magnitude, than that obtained from the precursor (non-fibrous, powder) sample (2.47 S m-1). The remarkable performance of the synthesized electrodes is ascribed to the robust network morphology and mesoporosity obtained by soft-templating from the phase-separated sacrificial polymer. This is a demonstration of lignin valorization for novel application in advanced materials.
  • Partitioning of the milk fat globule membrane between buttermilk and butter serum is determined by the thermal behaviour of the fat globules
    (2021-01) Hokkanen, Sanna P.; Partanen, Riitta; Jukkola, Annamari; Frey, Alexander D.; Rojas Gaona, Orlando
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Isolation of the industrially interesting milk fat globule membrane (MFGM) components from dairy streams is challenging, and a full exploitation of their benefits can be gained by better understanding of the behaviour of the fat globule membrane fraction during milk fat processing. In this study, microfiltration of the cream before churning and the comprehensive compositional analysis of the process streams revealed new insights on MFGM partitioning during the phase inversion in butter making. After removal of the smallest fat globules by microfiltration, a reduced phospholipid content was reflected in the buttermilk, but not in the butter serum. Regardless of the cream washing, buttermilk and butter serum lipids were different in PL-to-fat ratio, phospholipid composition, degree of unsaturation and melting behaviour. We suggest that partitioning of the MFGM fraction between butter and buttermilk is a direct result of the physico-chemical properties of the fat globules, partly related to the globule size.
  • Selective Laser Sintering of Lignin-Based Composites
    (2021-02-22) Ajdary, Rubina; Kretzschmar, Niklas; Bani Asadi, Hossein; Trifol Guzman, Jon; Seppälä, Jukka; Partanen, Jouni; Rojas Gaona, Orlando
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Lignin is introduced as a suitable component for selective laser sintering (SLS) of polyamide (PA12) to reduce costs while maintaining or improving processability and performance. Alkali lignin (sourced as a polydisperse, amorphous powder) was used at a volume concentration of up to 60 vol % for three-dimensional (3D) printing of complex, layered structures. The latter were obtained as high axial aspect objects, produced in flat, flipped (90°), and vertical directions, which were further examined to elucidate the effect of lignin as a suitable component in SLS. The composite withstood heating during SLS, and sintered PA/lignin showed 30% less degradation at elevated temperatures compared to pure PA. The morphological, wetting, mechanical, and thermal characteristics associated with the 3D-printed structures were compared. For instance, the strength and wettability were highly dependent on processing orientation. Compared to objects produced from neat PA, those that included lignin presented a higher porosity (∼10%) with a simultaneous increase in stiffness (increased Young modulus, by ∼16%, and reduced tensile strength, by ∼7%). Owing to differences in surface roughness and composition, an important difference in the water contact angle (CA) of the samples printed in the flipped and flat orientations was observed (55 and 126°, respectively). Overall, SLS is shown as a developmental step toward lignin valorization in composites while allowing reduced cost, scalability, and facile processing.
  • Spinning of Cellulose Nanofibrils into Filaments: A Review
    (2017) Lundahl, Meri; Klar, Ville; Wang, Ling; Ago, Mariko; Rojas Gaona, Orlando
     A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    Spinning of cellulose nanofibrils (CNF) offers promising opportunities to develop renewable fibers and filaments with strong, aligned structure. This review introduces recent findings on the relationship between the properties of CNF hydrogels, the spinning conditions and the performance of filaments obtained by dry- and wet-spinning. For example, the filament Young’s modulus correlates with CNF structural factors, such as slenderness and crystallinity. Furthermore, high shear rates and extensional flow strengthen the filament, mainly by improving structural uniformity and partly by effectively orienting the fibrils. However, other less obvious factors, such as those associated with coagulation and drying, play critical roles in filament performance. These and other details related to this timely application of CNF are presented here for the benefit of researchers and users of fibers and filaments for composites, textiles and others.