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Exploring factors afecting elementary school teachers' adoption of 3D printers in teaching
Branko Anđić, Andrej Šorgo, Christoph Helm, Robert Weinhandl, Vida Lang, 2023, original scientific article

Abstract: Owing to its advantages such as producing durable models and easy accessibility, 3D modeling and printing (3DMP) has become increasingly popular in educational practice and research. However, the results of many studies have shown that the adoption rate of 3DMP among teachers is still low, especially in elementary schools. Therefore, research is needed to expand current knowledge about what influences teachers' decisions to start and continue using 3DMP in elementary schools. To investigate factors that affect elementary school teachers' decisions to use 3D printing in teaching, this study uses a mixed methods research approach combining binary logistic regression with a qualitative thematic analysis approach. Both approaches assembled predictive constructs from a range of theories on (1) technology acceptance and (2) intentions to continue or abandon 3DMP use. Using a sample of 225 elementary teachers from Montenegro, this study empirically concluded that intentions to discontinue 3DMP was slightly more strongly correlated with the predictors (i.e., performance expectancy, effort expectancy, perceived pedagogical impact, personal innovativeness, management support, user interface quality, technology compatibility, social influence, student expectations) than was intentions to continue using 3DMP. Performance expectancy was a significant determinant of teachers’ continued use of a 3DMP approach. The remaining seven factors (constructs) were found to be insignificant predictors. Perceived pedagogical impact and technology compatibility were significantly associated with teachers' decisions to discontinue using 3DMP. Our results also suggest that the time required to use 3DMP during instruction, the impact of 3DMP on the implementation of curriculum activities, and the availability of 3D printers are all relevant factors that influence teachers’' decision to use or abandon 3DMP.
Keywords: elementary school, binary logistic regression, continuance intentions, thematic analysis approach, 3D modelling and printing
Published in DKUM: 26.03.2024; Views: 171; Downloads: 190
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Numerical analysis of a transtibial prosthesis socket using 3D-Printed Bio-Based PLA
Vasja Plesec, Jani Humar, Polona Dobnik-Dubrovski, Gregor Harih, 2023, original scientific article

Abstract: Lower-limb prosthesis design and manufacturing still rely mostly on the workshop process of trial-and-error using expensive unrecyclable composite materials, resulting in time-consuming, material-wasting, and, ultimately, expensive prostheses. Therefore, we investigated the possibility of utilizing Fused Deposition Modeling 3D-printing technology with inexpensive bio-based and bio-degradable Polylactic Acid (PLA) material for prosthesis socket development and manufacturing. The safety and stability of the proposed 3D-printed PLA socket were analyzed using a recently developed generic transtibial numeric model, with boundary conditions of donning and newly developed realistic gait cycle phases of a heel strike and forefoot loading according to ISO 10328. The material properties of the 3D-printed PLA were determined using uniaxial tensile and compression tests on transverse and longitudinal samples. Numerical simulations with all boundary conditions were performed for the 3D-printed PLA and traditional polystyrene check and definitive composite socket. The results showed that the 3D-printed PLA socket withstands the occurring von-Mises stresses of 5.4 MPa and 10.8 MPa under heel strike and push-off gait conditions, respectively. Furthermore, the maximum deformations observed in the 3D-printed PLA socket of 0.74 mm and 2.66 mm were similar to the check socket deformations of 0.67 mm and 2.52 mm during heel strike and push-off, respectively, hence providing the same stability for the amputees. We have shown that an inexpensive, bio-based, and bio-degradable PLA material can be considered for manufacturing the lower-limb prosthesis, resulting in an environmentally friendly and inexpensive solution.
Keywords: 3D printing, bio-based, polylactic acid, PLA, prosthesis, prosthesis socket, numerical model, finite element method
Published in DKUM: 14.03.2024; Views: 107; Downloads: 19
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Functional 3D printed polysaccharide derivative scaffolds for vascular graft application : doctoral disertation
Fazilet Gürer, 2023, doctoral dissertation

Abstract: Tissue engineering (TE) is an interdisciplinary field that aims towards replacement, healing or reconstruction of damaged tissue and organs. Incurable diseases are currently treated with organ transplantation, that have the disadvantages of insufficient donors, immune response, and organ rejection after transplantation. TE imitate the functions of extracellular matrix (ECM) to develop biocompatible/biodegradable scaffolds with appropriate features which are utilized to provide mechanical support, cellular infiltration, migration, and tissue formation, and to mimic the biochemical and biophysical cues of cells. Several fabrication methods have been introduced to mimic the 3D structure of ECM and 3D printing is one of the additive manufacturing techniques, widely used in TE because of its feasibility to build complex tissue constructs and control over fabrication and cell distribution. The polysaccharide-peptide conjugate has gained enormous interest in recent years owing to its biocompatibility, degradability, flexibility, and structural matching to natural proteoglycans. In this context, we reported here on investigation of biocompatibility with HUVECs, surface modification of 3D printed PCL scaffolds with an amine group and chemically crosslinked oxidized HA-amino acid/peptide conjugates (OHACs) was used to develop a novel biomaterial for use as a tissue engineered vascular graft. Modified polysaccharides were characterized with respect to their chemical structure, charge, UV and fluorescence properties and cytotoxicity. The successful conjugation was demonstrated by XPS, and a decrease in the free amine peaks on the surface was observed after conjugation. In addition, the water contact angle measurements showed improved wetting, an indication that the conjugation to the PCL-A surface was successful. Finally, the biocompatibility of the novel scaffolds was characterized by the MTS and the live- dead assay. In both assays, proliferation of cells was observed after 7 days and cell spreading on the surface was detected by phalloidin staining of actin filaments. In conclusion, it was possible to prepare surface-active scaffolds by combining the advantages of biocompatibility and mechanical strength of polysaccharides and polyesters, respectively.
Keywords: 3D tiskanje, karboksimetilceluloza, hialuronska kislina, polikaprolakton, kemija karbodiimida, kemija Shiffove baze, endotelizacija 3D printing, carboxymethyl cellulose, hyaluronic acid, polycaprolactone, carbodiimide chemistry, shiff-base chemistry, endothelialization
Published in DKUM: 06.10.2023; Views: 352; Downloads: 39
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Synergistic effect of screen-printed Al(OH)[sub]3 nanoparticles and phosphorylated cellulose nanofibrils on the thermophysiological comfort and high-intensive heat protection properties of flame-retardant fabric
Tjaša Kolar, Jelka Geršak, Nataša Knez, Vanja Kokol, 2022, original scientific article

Abstract: Al(OH)3 nanoparticles (ATH NPs) and phosphorylated cellulose nanofibrils (PCNFs) were used as user-friendly and comfortable coating components on flame-retardant fabric to improve its thermophysiological comfort and high-intensive heat protection properties. The effect of the PCNF imprinting and its attachment after the post-printing of a hydrophobic polyacrylate (AP) on the same (back side) or the other (front) side of the fabric, with and without the addition of ATH NPs, was considered, to maintain the front side (facing the wearer) as hydrophilic while keeping the back side (facing the outside) hydrophobic. The amount of coatings applied and their patterning were studied, varied with the ATH NPs’ concentration (1.7, 3.3 and 6.7 wt%) and screen mesh size used (60 and 135), based on the coating’ mass, fabric’s air permeability, thickness and microstructure. The reduced moisture build-up (55%), increased the water vapour (13%) and heat (12%) transfer from the skin, were assessed by applying PCNF under the AP, being more pronounced in the case of using a 135 mesh-sized screen, given the smaller, more densely distributed, thinner and imprinted pattern coatings. These effects were further improved by the addition of nanoporous ATH NPs, which allowed more homogeneous spreading of the moisture and its faster transport. Such a treatment also shifted the fabric’s degradation temperature towards higher values (up to 15°C), retained up to 30% of high-heat flux (21 kW/m2), prolonged the time to ignition by 11 s and reduced the total heat released by up to 60%, thereby providing better protection when exposed to the heat, due to the presence of the phosphorous (PCNF) promoted generation of an Al2O3 char acting as a barrier layer, while also reducing the production of heat and generation of smoke by 75%.
Keywords: tekstilna tehnologija, ognjevaren tekstil, Al(OH)3 nanodelci, celulozni nanofibrili, tiskanje tekstilij, optične lastnosti, termofiziološko udobje, toplotna zaščita, flame-retardant textile, Al(OH)3 nanoparticles, phosphorylated cellulose nanofibrils, screen-printing, thermophysiological comfort, heat protection
Published in DKUM: 12.07.2023; Views: 344; Downloads: 11
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Comparative study of the microstructure and properties of cast-fabricated and 3D-printed laser-sintered Co–Cr alloys for removable partial denture frameworks
Dejan Stamenković, Miljana Popović, Rebeka Rudolf, Milorad Zrilić, Karlo Raić, Kosovka Obradović-Đuričić, Dragoslav Stamenković, 2023, original scientific article

Abstract: Since additive technologies in dentistry are gradually replacing metal casting technology, it is necessary to evaluate new dental constructions intended for the development of removable partial denture frameworks. The aim of this research was to evaluate the microstructure and mechanical properties of 3D-printed, laser-melted and -sintered Co–Cr alloys, and perform a comparative study with Co–Cr castings for the same dental purposes. The experiments were divided into two groups. The first group consisted of samples produced by conventional casting of the Co–Cr alloy. The second group consisted of 3D-printed, laser-melted and -sintered specimens produced from a Co–Cr alloy powder divided into three subgroups, depending on the technological parameters chosen for manufacturing (angle, location and heat treatment). Examination of the microstructure was carried out by classical metallographic sample preparation, using optical microscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy (EDX) analysis. A structural phase analysis was also performed by XRD. The mechanical properties were determined using a standard tensile test. The microstructure observation showed a dendritic character in the case of castings, while in the case of 3D-printed, laser-melted and -sintered Co–Cr alloys, the microstructure was typical for additive technologies. The XRD phase analysis confirmed the presence of Co–Cr phases (ε and γ). The results of the tensile test showed remarkably higher yield and tensile strength values and slightly lower elongation of the 3D-printed, laser-melted and -sintered samples than those produced by conventional casting.
Keywords: Co–Cr dental alloys, 3D printing, laser melting and sintering, casting, microstructure, mechanical properties, characterization
Published in DKUM: 21.04.2023; Views: 369; Downloads: 31
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Preparation of Three Dimensional Structures of Polysaccharide Derivatives for Application in Regenerative Medicine : doctoral disertation
Andreja Dobaj-Štiglic, 2022, doctoral dissertation

Abstract: Biocompatible polysaccharide scaffolds with controllable pore size, good mechanical properties, and no hazardous chemical crosslinkers are desirable for long-term tissue engineering applications. Despite decades of development of novel scaffolds, there are still many challenges to be solved regarding their production and optimization for specifically engineered tissues. Herein, we have fabricated several three-dimensional (3D) scaffolds using polysaccharide or polysaccharide-protein composite hydrogels or inks for 3D printing, featuring strong shear thinning behavior and adequate printability. The inks, composed of various combinations of chitosan, nanofibrillated cellulose, carboxymethyl cellulose, collagen, and citric acid, were 3D printed, freeze-dried, and dehydrothermally heat-treated to obtain dimensionally and mechanically stable scaffolds. The heat-assisted step induced the formation of covalent amide and ester bonds between the functional groups of chosen polysaccharides and protein collagen. Citric acid was chosen as a non-hazardous and „green” crosslinker to further tailor the mechanical properties and long-term stability of the scaffolds. We have investigated how the complexation conditions, charge ratio, dehydrothermal treatment, and degree of crosslinking influence the scaffolds' chemical, surface, swelling, and degradation properties in the dry and hydrated states. The compressive strength, elastic modulus, dimensional stability and shape recovery of the (crosslinked) scaffolds increased significantly with balanced charge ratio, dehydrothermal treatment, and increased concentrations of citric acid crosslinker and collagen concentrations. The prepared crosslinked scaffolds promoted (clustered) cell adhesion and showed no cytotoxic effects, as determined by cell viability assays and live/dead staining with human bone tissue-derived osteoblasts and human adipose tissue-derived mesenchymal stem cells. The water-based and non-hazardous crosslinking methods presented here can be extended to all polysaccharide- or polysaccharide-protein-based materials to develop cell-friendly scaffolds with tailored properties suitable for various tissue engineering applications.
Keywords: chitosan, carboxymethyl cellulose, nanofibrillated cellulose, citric acid, collagen, freeze drying, 3D printing, dehydrothermal treatment
Published in DKUM: 11.10.2022; Views: 564; Downloads: 150
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