| 1. |
- Ahlinder, Astrid
(författare)
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Degradable copolymers in additive manufacturing: controlled fabrication of pliable scaffolds
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Inom vävnadsregenerering är produktionen av väldefinieradematriser med en porös arkitektur av nedbrytbara polymerer av stortintresse, dessa kan nu skapas genom additiva tillverkningsprocesser. Vidadditiv tillverkning krävs ett smalt munstycke för att skapa detaljrikastrukturer och detta ställer krav på att de reologiska egenskapernaanpassat. Lägre viskositet av smältan gör de lättare att använda, men enhög molmassa krävs för tillverka matriser där de mekaniska egenskapernakan bibehållas under tiden som krävs för vävnadsregenerering. Ytterligareen utmaning uppstår när nedbrytbara polymerer används i smältbaseradadditiva tillverkningsprocesser är att termisk nedbrytning ofta reducerarmolmassan redan under produktionsfasen. För att kunna användanedbrytbara polymerer av medicinsk kvalitet i smältbaserad additivtillverkning och samtidigt minimera den termiska nedbrytningen har, idenna avhandling, reologiska fingeravtryck av nedbrytbara syntetiskapolymerer med medicinsk kvalitet använts för att bestämmaprocessparametrar. Termisk nedbrytning beroende av processparamaterar har analyserats och minimeras i två smältbaserade additivatillverkningsprocesser.En additiv tillverkningsprocess var designad där nedbrytbarapolymerer av hög molmassa kunde användas utan termisk nedbrytning närprocessparametrar hade valts utifrån polymerens egenskaper. Kunskapenom användningen av dessa polymerer inom additiv tillverkning kundeappliceras på en sampolymer som utvecklats inom forskningsgruppen förmjukvävnad, poly(ε-kaprolakton-co-p-dioxanon) för att skapa böjbaramatriser. Genom att använda reologisk analys och polymerkarakteriseringerhölls processparametrar som möjliggjorde additiv tillverkning utantermisk nedbrytning. I tillägg till val av polymer och processparametrar såkan mekaniska egenskaper också styras av den strukturella designen.Poly(ε-kaprolakton) användes som modellmaterial för att reducerastyvheten med hjälp av designen, resultatet visade att det var möjligt medmer än en faktor 10 och mjuka böjbara matriser skapades.
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| 2. |
- Ahlinder, Astrid, et al.
(författare)
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Development of a solid food simulant to evaluate migration of chemicals from paper and board food contact materials to moist food
- 2024
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Ingår i: Food Packaging and Shelf Life. - : Elsevier Ltd. - 2214-2894. ; 45
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Tidskriftsartikel (refereegranskat)abstract
- Food contact materials (FCMs) i.e. materials that food is packaged or handled in, must be safe for their intended use. European FCM legislation uses a risk-based approach, with a cornerstone of FCM’s safety evaluation being measurement of migration of substances from FCMs to food simulants. The standard methods mainly developed for plastic FCMs are not always suitable for less inert and moisture sensitive materials such as paper and board. However, these are becoming increasingly common as FCMs e.g. to replace single-use plastics. In addition, there is a drive to further use recycled materials. To support this development, new methods for assessing the safety of these materials are needed. In the present feasibility study, a hydrogel crosslinked through freeze-thawing of poly(vinyl alcohol) was evaluated as a food simulant for moist foods. The migration of surrogate compounds from a spiked paperboard to the hydrogel was determined and compared to the migration to a real moist food (a slice of apple), the commonly used modified polyphenylene oxide (MPPO) and a water extract. Migration of polar surrogates to the hydrogel correlated well with the migration to the apple slice. However, our results indicate that the hydrogel is less suitable as simulant for non-polar surrogates. Overall, the study demonstrates the potential of this hydrogel-based simulant for improving risk assessment of less inert FCMs.
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| 3. |
- Ahlinder, Astrid, et al.
(författare)
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Medical grade polylactide, copolyesters and polydioxanone : Rheological properties and melt stability
- 2018
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Ingår i: Polymer testing. - : ELSEVIER SCI LTD. - 0142-9418 .- 1873-2348. ; 72, s. 214-222
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Tidskriftsartikel (refereegranskat)abstract
- Rheological measurements have shown that lactide-based copolymers with L-lactide content between 50 and 100 mol% with varying comonomers, as well as polydioxanone (PDX), can be used in additive manufacturing analogously to poly(L-lactide) (PLLA) if their melt behaviour are balanced. The results indicate that copolymers can be melt processed if the temperature is adjusted according to the melting point, and parameters such as the speed are tuned to conteract the elastic response. Small amplitude oscillatory shear (SAOS) rheology, thermal and chemical characterisation allowed us to map the combined effect of temperature and frequency on the behaviour of six degradable polymers and their melt stability. Values of complex viscosity and Tan delta obtained through nine time sweeps by varying temperature and frequency showed that the molecular structure and the number of methylene units influenced the results, copolymers of L-lactide with D-Lactide (PDLLA) or glycolide (PLGA) had an increased elastic response, while copolymers with trimethylene carbonate (PLATMC) or epsilon-caprolactone (PCLA) had a more viscous behaviour than PLLA, with respect to their relative melting points. PDLLA and PLGA require an increased temperature or lower speed when processed, while PLATMC and PCLA can be used at a lower temperature and/or higher speed than PLLA. PDX showed an increased viscosity compared to PLLA but a similar melt behaviour. Negligible chain degradation were observed, apart from PLGA.
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| 4. |
- Ahlinder, Astrid, et al.
(författare)
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Minimise thermo-mechanical batch variations when processing medical grade lactide based copolymers in additive manufacturing
- 2020
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Ingår i: Polymer degradation and stability. - : Elsevier BV. - 0141-3910 .- 1873-2321. ; 181
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Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing is suitable for producing complex geometries; however, variation in thermo-mechanical properties are observed during one batch cycle when degradable aliphatic polyesters of medical grade are used in melt extrusion-based methods. This is one important reason for why additive manufacturing has not yet been fully utilised to produce degradable medical implants. Herein, the internal variation has been minimised during one batch cycle by assessing the effect of different processing parameters when using commercially available medical grade copolymers. To minimise the molar mass, thermal and mechanical variation within one batch cycle, the rheological fingerprint of the commercially available medical grade poly(L-lactide-co-ε-caprolactone) and poly(L-lactide-co-trimethylene carbonate) has been correlated to the process parameters of the ARBURG Plastic Freeforming. An increase in the temperature up to 220°C and the associated increase in pressure are beneficial for the viscoelastic and thermally stable poly(L-lactide-co-ε-caprolactone). In contrast, a temperature below 220°C should be used for the poly(L-lactide-co-trimethylene carbonate) to reduce the variation in strain at break during one batch cycle. The residence time is decreased through the increase of the discharge parameter. An increase in temperature is however required to reduce the viscosity of the polymer and allow the pressure to stay within the machine limitations at higher discharge parameters. The results are highly relevant to the development of additive manufacturing for the production of degradable medical devices with identical properties. In fact, Food and Drug Administration guidelines for additive manufacturing of medical implants specify the need to control changes in material properties during the process.
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| 5. |
- Ahlinder, Astrid, et al.
(författare)
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Nondegradative additive manufacturing of medical grade copolyesters of high molecular weight and with varied elastic response
- 2020
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Ingår i: Journal of Applied Polymer Science. - : WILEY. - 0021-8995 .- 1097-4628. ; 137:15
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Tidskriftsartikel (refereegranskat)abstract
- Although additive manufacturing through melt extrusion has become increasingly popular as a route to design scaffolds with complex geometries the technique if often limited by the reduction in molecular weight and the viscoelastic response when degradable aliphatic polyesters of high molecular weight are used. Here we use a melt extruder and fused filament fabrication printer to produce a reliable nondegradative route for scaffold fabrication of medical grade copolymers of L-lactide, poly(epsilon-caprolactone-co-L-lactide), and poly(L-lactide-co-trimethylene carbonate). We show that degradation is avoided using filament extrusion and fused filament fabrication if the process parameters are deliberately chosen based upon the rheological behavior, mechanical properties, and polymer composition. Structural, mechanical, and thermal properties were assessed throughout the process to obtain comprehension of the relationship between the rheological properties and the behavior of the medical grade copolymers in the extruder and printer. Scaffolds with a controlled architecture were achieved using high-molecular-weight polyesters exhibiting a large range in the elastic response causing negligible degradation of the polymers.
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| 6. |
- Ahlinder, Astrid, et al.
(författare)
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Towards attractive texture modified foods with increased fiber content for dysphagia via 3D printing and 3D scanning
- 2023
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Ingår i: Frontiers in Food Science and Technology. - : Frontiers Media S.A.. - 2674-1121. ; 2
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Tidskriftsartikel (refereegranskat)abstract
- As life expectancy increases so do age related problems such as swallowing disorders, dysphagia, which affects 10%–30% of people over 65 years old. For dysphagia patients the texture and rheological properties of the food, and the bolus, is critical to avoid choking and pneumonia. Texture modified foods, timbals, are often served to these patients due to their ease of swallowing. The main concern with these foods is that they do not look visually alike the food they replace, which can decrease the patient’s appetite and lead to reduced food intake and frailty. This study aims to improve both the visual appearance of texturized food as well as the energy density and fiber content of the timbal formulation. 3D scanning and additive manufacturing (3D Printing) were used to produce meals more reminiscent of original food items, increasing their visual appeal. Rheology was used to ensure the original flow profile was maintained as the timbal was reformulated by reducing starch contents and partially replacing with dietary fibers. The amount of starch was reduced from 8.7 wt% in the original formulation to 3.5 wt% and partially replaced with 3 wt% citrus fiber, while maintaining properties suitable for both swallowing and 3D printing. The resulting formulation has improved nutritional properties, while remaining suitable for constructing visually appealing meals, as demonstrated by 3Dprinting a chicken drumstick from a model generated with 3D scanning.
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| 7. |
- Fuoco, Tiziana, PhD, 1986-, et al.
(författare)
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Poly(epsilon-caprolactone-co-p-dioxanone) : a Degradable and Printable Copolymer for Pliable 3D Scaffolds Fabrication toward Adipose Tissue Regeneration
- 2020
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Ingår i: Biomacromolecules. - : AMER CHEMICAL SOC. - 1525-7797 .- 1526-4602. ; 21:1, s. 188-198
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Tidskriftsartikel (refereegranskat)abstract
- The advancement of 3D printing technologies in the fabrication of degradable scaffolds for tissue engineering includes, from the standpoint of the polymer chemists, an urgent need to develop new materials that can be used as ink and are suitable for medical applications. Here, we demonstrate that a copolymer of epsilon-caprolactone (CL) with low amounts of p-dioxanone (DX) (15 mol %) is a degradable and printable material that suits the requirements of melt extrusion 3D printing technologies, including negligible degradation during thermal processing. It is therefore a potential candidate for soft tissue regeneration. The semicrystalline CL/DX copolymer is processed at a lower temperature than a commercial polycaprolactone (PCL), shaped as a filament for melt extrusion 3D printing and as porous and pliable scaffolds with a gradient design. Scaffolds have Young's modulus in the range of 60-80 MPa, values suitable for provision of structural support for damaged soft tissue such as breast tissue. SEM and confocal microscope indicate that the CL/DX copolymer scaffolds support adipose stem cell attachment, spreading, and proliferation.
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| 8. |
- Liu, Hailong, et al.
(författare)
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Computational and experimental characterization of 3D-printed PCL structures toward the design of soft biological tissue scaffolds
- 2020
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 188
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Tidskriftsartikel (refereegranskat)abstract
- Degradable porous polymeric structures are attractive candidates for biological tissue scaffolds, and adequate mechanical, transport, chemical and biological properties determine their functionality. Aside from the properties of polymer-based materials, the scaffold's meso-structure controls its elasticity at the organ length-scale. This study investigated the effect of the meso-structure on scaffolds' mechanical and transport properties using finite element analysis (FEA) and computational fluid dynamics (CFD). A number of poly (ε-caprolactone) (PCL) - based scaffolds were 3D printed, analyzed by microcomputed tomography (micro-CT) and mechanically tested. We found that the gradient (G) and gradient and staggered (GS) meso-structure designs led to a higher scaffold permeability, a more homogeneous flow inside the scaffold, and a lower wall shear stress (WSS) in comparison with the basic (B) meso-structure design. The GS design resulted in scaffold stiffness as low as 1.07/0.97 MPa under compression/tension, figures that are comparative with several soft tissues. Image processing of micro-CT data demonstrated that the imposed meso-structures could have been adequately realized through 3D printing, and experimental testing validated FEA analysis. Our results suggest that the properties of 3D-printed PCL-based scaffolds can be tuned via meso-structures toward soft tissue engineering applications. The biological function of designed scaffolds should be further explored in-situ studies.
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| 9. |
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| 10. |
- Navarro, J. R. G., et al.
(författare)
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Surface-Initiated Controlled Radical Polymerization Approach to in Situ Cross-Link Cellulose Nanofibrils with Inorganic Nanoparticles
- 2020
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 21:5, s. 1952-1961
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates a strategy to convert hydrophilic cellulose nanofibrils (CNF) into a hydrophobic highly cross-linked network made of cellulose nanofibrils and inorganic nanoparticles. First, the cellulose nanofibrils were chemically modified through an esterification reaction to produce a nanocellulose-based macroinitiator. Barium titanate (BaTiO3, BTO) nanoparticles were surface-modified by introducing a specific monomer on their outer-shell surface. Finally, we studied the ability of the nanocellulose-based macroinitiator to initiate a single electron transfer living radical polymerization of stearyl acrylate (SA) in the presence of the surface-modified nanoparticles. The BTO nanoparticles will transfer new properties to the nanocellulose network and act as a cross-linking agent between the nanocellulose fibrils, while the monomer (SA) directly influences the hydrophilic-lipophilic balance. The pristine CNF and the nanoparticle cross-linked CNF are characterized by FTIR, SEM, and solid-state 13C NMR. Rheological and dynamic mechanical analyses revealed a high dregee of cross-linking.
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