Unidade de Investigação - CDRsp – Centro para o Desenvolvimento Rápido e Sustentado de Produto
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- 316L stainless steel mechanical and tribological behavior—A comparison between selective laser melting, hot pressing and conventional castingPublication . Bartolomeu, F.; Buciumeanu, M.; Pinto, E.; Alves, Nuno; Carvalho, O.; Silva, F: S.; Miranda, G.This work presents a comprehensive study on the influence of three different processing technologies (Selective Laser Melting, Hot Pressing and conventional casting) on the microstructure, mechanical and wear behavior of an austenitic 316L Stainless Steel.Acorrelation between the processing technologies,the obtained microstructure and the mechanical and wear behavior was achieved. The results showed that the highest mechanical properties and tribological performance were obtained for 316L SS specimens produced by Selective Laser Melting, when compared to Hot Pressing and conventional casting. The high wear and mechanical performance of 316L Stainless Steel fabricated by Selective Laser Melting are mainly due to the finer microstructure, induced by the process. In this sense, Selective Laser Melting seems a promising method to fabricate customized 316L SS implants with improved mechanical and wear performance
- 3D printing of new biobased unsaturated polyesters by microstereo-thermal-lithographyPublication . Gonçalves, Filipa A. M. M.; Costa, Cátia S. M. F.; Fabela, Inês G. P.; Farinha, Dina; Faneca, Henrique; Simões, Pedro N.; Serra, Arménio C.; Bártolo, Paulo J.; Coelho, Jorge F. J.New micro three-dimensional (3D) scaffolds using biobased unsaturated polyesters (UPs) were prepared by microstereo-thermal-lithography (μSTLG). This advanced processing technique offers indubitable advantages over traditional printing methods. The accuracy and roughness of the 3D structures were evaluated by scanning electron microscopy and infinite focus microscopy, revealing a suitable roughness for cell attachment. UPs were synthesized by bulk polycondensation between biobased aliphatic diacids (succinic, adipic and sebacic acid) and two different glycols (propylene glycol and diethylene glycol) using fumaric acid as the source of double bonds. The chemical structures of the new oligomers were confirmed by proton nuclear magnetic resonance spectra, attenuated total reflectance Fourier transform infrared spectroscopy and matrix assisted laser desorption/ionization-time of flight mass spectrometry. The thermal and mechanical properties of the UPs were evaluated to determine the influence of the diacid/glycol ratio and the type of diacid in the polyester's properties. In addition an extensive thermal characterization of the polyesters is reported. The data presented in this work opens the possibility for the use of biobased polyesters in additive manufacturing technologies as a route to prepare biodegradable tailor made scaffolds that have potential applications in a tissue engineering area.
- 3D shape prior active contours for an automatic segmentation of a patient specific femur from a CT scanPublication . Almeida, D.; Folgado, J.; Fernandes, P.R.; Ruben, RuiThe following paper describes a novel approach to a medical image segmentation problem. The fully automated computational procedure receives as input images from CT scan exams of the human femur and returns a three dimensional representation of the bone. This patient specific iterative approach is based in 3D active contours without edges, implemented over a level set framework, on which the evolution of the contour depends on local image parameters which can easily be defined by the user but also on a priori information about the volume to segment. This joint approach will lead to an optimal solution convergence of the iterative method. The resulting point cloud can be an excellent starting point for a Finite Element mesh generation and analysis or the basis for a stereolitography for example.
- Biomanufacturing for tissue engineering: Present and future trendsPublication . Bartolo, Paulo; Chua, C. K.; Almeida, Henrique de Amorim; Chou, S. M.; Lim, A. S. C.Tissue engineering, often referred to as regenerative medicine and reparative medicine, is an interdisciplinary field that necessitates the combined effort of cell biologists, engineers, material scientists, mathematicians, geneticists, and clinicians toward the development of biological substitutes that restore, maintain, or improve tissue function. It has emerged as a rapidly expanding approach to address the organ shortage problem and comprises tissue regeneration and organ substitution. Cells placed on/or within constructs is the most common strategy in tissue engineering. Successful cell seeding depends on fast attachment of cell to scaffolds, high cell survival and uniform cell distribution. The seeding time is strongly dependent on the scaffold material and architecture. Scaffolds provide an initial biochemical substrate for the novel tissue until cells can produce their own extra-cellular matrix (ECM). Thus scaffolds not only define the 3D space for the formation of new tissues, but also serve to provide tissues with appropriate functions. These scaffolds are often critical, both in vivo (within the body) or in vitro (outside the body) mimicking in vivo conditions. Additive fabrication processes represent a new group of non-conventional fabrication techniques recently introduced in the biomedical engineering field. In tissue engineering, additive fabrication processes have been used to produce scaffolds with customised external shape and predefined internal morphology, allowing good control of pore size and pore distribution. This article provides a comprehensive state-of-the-art review of the application of biomanufacturing additive processes in the field of tissue engineering. New and moving trends in biomanufacturing technologies and the concept of direct cell-printing technologies are also discussed.
- Biomechanically Inspired Shape Memory Effect Machines Driven by Muscle like Acting NiTi AlloysPublication . Raffaella Aversa; Francesco Tamburrino; Relly Victoria V. Petrescu; Florian Ion T. Petrescu; Mateus, Artur; Guanying, Chen; Antonio ApicellaThe research shows a bioinspired approach to be adopted to design of systems based on Shape Memory Alloys (SMAs), a class of Smart Materials that has in common with muscles the capability to react to an impulse (thermal for SMAs) with a contraction. The biomechanically inspired machine that is discussed in the paper refers to the antagonistic muscles pairs, which belongs to the Skeletal Muscles and are normally arranged in opposition so that as one group of muscles contract another group relaxes or lengthens. The study proposes a model, a solution not only to design a specific application, but also to provide an approach to be used for a wide range of adaptive applications (switchable windows, smart shadow systems, parking and urban shelters, etc.), where the shape changes in response to different external stimuli. The use of antagonist pairs mechanism provides a solution for better optimized systems based on SMAs where the main and proven advantages are: Easier and faster change of shape, lower need of energy for system operation, lower cost for SMA training and no problem of overheating.
- Choosing sheep (Ovis aries) as animal model for temporomandibular joint research: Morphological, histological and biomechanical characterization of the joint discPublication . Angelo, D.F.; Morouço, P.; Alves, N.; Viana, T.; Santos, F.; González, R.; Monje, F.; Macias, D.; Carrapiço, B.; Sousa, R.; Cavaco-Gonçalves, S.; Salvado, F.; Peleteiro, C.; Pinho, M.Preclinical trials are essential to the development of scientific technologies. Remarkable molecular and cellular research has been done using small animal models. However, significant differences exist regarding the articular behavior between these models and humans. Thus, large animal models may be more appropriate to perform trials involving the temporomandibular joint (TMJ). The aim of this work was to make a morphological (anatomic dissection and white light 3D scanning system), histological (TMJ in bloc was removed for histologic analysis) and biomechanical characterization (tension and compression tests) of sheep TMJcomparing the obtained results with human data. Results showed that sheep processus condy-laris and fossa mandibularis are anatomically similar to the same human structures. TMJ dischas an elliptical perimeter, thinner in the center than in periphery. Peripheral area actsas a ring structure supporting the central zone. The disc cells display both fibroblast andchondrocyte-like morphology. Marginal area is formed by loose connective tissue, with somechondrocyte-like cells and collagen fibers in diverse orientations. Discs obtained a tensile mod-ulus of 3.97 ± 0.73 MPa and 9.39 ± 1.67 MPa, for anteroposterior and mediolateral assessment.The TMJ discs presented a compressive modulus (E) of 446.41 ± 5.16 MPa and their maximumstress value ( max) was 18.87 ± 1.33 MPa. Obtained results suggest that these animals should beconsidered as a prime model for TMJ research and procedural training. Further investigationsin the field of oromaxillofacial surgery involving TMJ should consider sheep as a good animalmodel due to its resemblance of the same joint in humans.© 2016 Elsevier Masson SAS. All rights reserved.
- Comparison by computer fluid dynamics of the drag force acting upon two helmets for wheelchair racersPublication . Forte, P; Marinho, D. A.; Morouço, P; Pascoal-Faria, P.; Barbosa, T. M.The aim of this study was to compare the drag force created by two helmets (time trial and road)used by a wheelchair racer. The head and helmet of the racer were scanned to obtain the3D models. Numerical simulation was run on Fluent, having as output the drag force for both helmets (road and time trial) in two different positions (0º and 90º) and increasing velocities (from 2.0 to 6.5 m/s). The greatest aerodynamic drag was noted wearing a time trial helmet in 90º ranging from 0.1025N to 0.8475N; this was also the position with the highest drag. The velocity with higher drag for booth helmets was at 6.5 m/s. The time trial helmet at 0º had the lower aerodynamic drag, compared with the same position of road helmet. The drag force seems to be lower wearing the time trial helmet and keeping the 0º position and, thus, should be considered for sprinting events.
- Comparison of Three-dimensional Extruded Poly (ɛ-Caprolactone) and Polylactic acid Scaffolds with Pore size VariationPublication . Monteiro de Moura, Carla Sofia; Ferreira, Frederico Castelo; Bártolo, Paulo JorgeAdditive manufacturing (AM) has become a prominent approach among the scientific community for the production of three-dimensional (3D) matrices able to support tissue engineering approaches, promoting cell adhesion, proliferation and organization aiming to repair different tissues, such as bone or cartilage. In this study we used an extrusion-based technique for the production of poly (ɛ-caprolactone) (PCL) and polylactic acid (PLA) scaffolds and performed a side-by-side scaffold characteristics comparison. Using this technique we were able to create fully 3D interconnected porous scaffolds with pore size variations ranging from 190 μm to 390 μm with both materials. These scaffolds were assessed for stiffness, wettability and cell adhesion using mesenchymal stem/stromal cells (MSC). Comparisons between these two materials were made. The compressive modulus obtained is on the same order of magnitude for both materials. However, PCL presents a statistically significant higher compressive modulus. Results confirmed that PCL is a more hydrophobic material, so it presents a lower wettability when compared to PLA. Interestingly cell adhesion is similar for PLA and PCL, therefore selection between these two materials for the use of this versatile platform can be defined according with biodegradability aimed.
- Controlled in Vitro Release of Levodopa from Sodium Alginate MembranesPublication . Franco, Margarida; Biscaia, Sara; Viana, Tânia; Alves, Nuno; Morouço, PedroLevodopa (LD) plays a central role in Parkinson’s Disease therapeutics. In this study, we aimed to encapsulate LD in sodium alginate (SA) membranes, and to study its dissolution profiles. Two types of SA membranes, loaded with two different amounts of LD were prepared and compared (M1: 85 mg per 50 ml SA/LD; M2: 127.5 mg per 75 ml SA/LD); membranes production followed a solvent-casting methodology. Calcium chloride was used as a crosslinking agent. LD solubility tests were performed to predict sink conditions required for complete drug dissolution. LD dissolution assays were carried out and UV spectrophotometry was used for cumulative release percentage determination. The obtained data were mathematically evaluated and fitted into mathematical dependent models; the difference factor (f1), the similarity factor (f2) and other parameters like dissolution efficiency (DE) were also used. No differences in the dissolution profiles of both membranes were noticed. Thus, increasing the amount of LD, but keeping the same concentration, led to a similar controlled release. The membranes presented in this work are expected to be a promising contribution in the development of a new controlled drug delivery system for LD administration.
- Controlling Morphology Using Low Molar Mass NucleatorsPublication . Mitchell, Geoffrey; Wangsoub, Supatra; Nogales, Aurora; Davis, Fred J.; Olley, Robert H.Crystallisation is a hugely important process in physical sciences and is crucial to many areas of, for example, chemistry, physics, biochemistry, metallurgy and geology. The process is typically associated with solidification, for example in the purification of solids from a heated saturated solution familiar to all chemistry undergraduates. Crystalline solids are also often the end result of cooling liquids, or in some cases gases, but in order to form require nucleation, in the absence of nucleation supercoiling of liquids well below the melting point is possible (Cava-gna, 2009). The quality of crystals, as gauged by size and levels of order is highly variable, and may depend on factors such as material purity and the rate of cool-ing; rapid cooling may result in poor crystallisation, or even the formation of amorphous materials with no long range order. In geological systems rates of cooling may vary over many orders of magnitude, for example obsidian is a large-ly amorphous material produced when lava is rapidly cooled (Tuffen, 2003), while the gypsum crystals found in the Cueva de los Cristales in Chihuahua, Mexico can reach 10 metres in length (Figure 1) and are formed over hundreds of thousands of years. In this latter case the formation of such large spectacular structures as shown in Figure 1 can only be explained by a low nucleation rate (García-Ruiz, 2007; Van Driessche, 2011).