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- Improving the process of making rapid prototyping models from medical ultrasound imagesPublication . Vaezi, Mohammad; Chua, Chee Kai; Chou, Siaw MengPurpose – Today, medical models can be made by the use of medical imaging systems through modern image processing methods and rapid prototyping (RP) technology. In ultrasound imaging systems, as images are not layered and are of lower quality as compared to those of computerized tomography (CT) and magnetic resonance imaging (MRI), the process for making physical models requires a series of intermediate processes and it is a challenge to fabricate a model using ultrasound images due to the inherent limitations of the ultrasound imaging process. The purpose of this paper is to make high quality, physical models from medical ultrasound images by combining modern image processing methods and RP technology. Design/methodology/approach – A novel and effective semi-automatic method was developed to improve the quality of 2D image segmentation process. In this new method, a partial histogram of 2D images was used and ideal boundaries were obtained. A 3D model was achieved using the exact boundaries and then the 3D model was converted into the stereolithography (STL) format, suitable for RP fabrication. As a case study, the foetus was chosen for this application since ultrasonic imaging is commonly used for foetus imaging so as not to harm the baby. Finally, the 3D Printing (3DP) and PolyJet processes, two types of RP technique, were used to fabricate the 3D physical models. Findings – The physical models made in this way proved to have sufficient quality and shortened the process time considerably. Originality/value – It is still a challenge to fabricate an exact physical model using ultrasound images. Current commercial histogram-based segmentation method is time-consuming and results in a less than optimum 3D model quality. In this research work, a novel and effective semi-automatic method was developed to select the threshold optimum value easily.
- Structure–property relationships in polyethylene based films obtained by blow molding as model system of industrial relevancePublication . Duraccio, Donatella; Mauriello, Amalia; Cimmino, Sossio; Silvestre, Clara; Auriemma, Finizia; Rosa, Claudio de; Pirozzi, Beniamino; Mitchell, Geoffrey RobertA method for the study of structure-property relationships of polyethylene (PE)-based films of potential use in food packaging has been set up. The approach has been demonstrated in the case of films obtained by blow-molding using model mixtures of two different polyethylenes, namely a metallocene-made grade of linear low density polyethylene (mLLDPE) and a low density polyethylene (LDPE). We show that physical properties important for numerous applications of these films, such as water vapor and oxygen permeability, toughness and stress strength, are related to the molecular structure and structural and morphological parameters of the blends, in particular, thickness of amorphous layers in lamellar stacks, lamellar thickness, lamellar twisting, and degree and type of branching.
- Obtención de andamios biodegradables mediante bioextrusiónPublication . Loaiza, Marielys C.; Sabino, Marcos A.; Bártolo, Paulo Jorge; Domingos, Marco; Müller, Alejandro J.En esta investigación se obtuvieron andamios biodegradables de mezclas de poli-(ácido láctico)/poli-(ε-caprolactona) (PLA/PCL) obtenidas en solución, cuyas proporciones en peso/peso (p/p) fueron 100/0, 90/10, 80/20, 0/100, mediante la técnica de biofabricación conocida como bioextrusión. Todas las mezclas fueron caracterizadas por Espectroscopía Infrarroja por Transformada de Fourier (FT-IR) y Calorimetría Diferencial de Barrido (DSC), observándose la variación en la morfología y la cristalinidad cuando el material se encontraba orientado (andamios) y sin orientar (mezclas iniciales). Mediante Microscopía Electrónica de Barrido (MEB) se observó la distribución de orientación, porosidad e interconectividad, características de un andamio biodegradable.
- Strain sequence effect on fatigue life and fracture surface topography of 7075-T651 aluminium alloyPublication . Macek, Wojciech; Branco, Ricardo; Costa, José Domingos; Pereira, CândidaThe paper studies the effect of strain-loading sequence on fatigue lifetime and fracture surface topographies in 7075-T651 aluminum alloy specimens. Fatigue tests were performed in two ways: (i) constant-amplitude loading and (ii) two series of variable amplitude loading with non-zero mean strain values. The topography of the fatigue fractures was measured over their entire surfaces with the help of an optical confocal measurement system. The results of fatigue tests in the form of equivalent strains, εaeq, such as the weighted mean of strain components, εa1, εa2, and fatigue life, Nf, were used as the sum of the partial number of cycles N1, and N2. This study indicates, inter alia, that the values of the fracture surface parameter core height Sk, found in the two-step loading program, are linearly dependent on the equivalent strain, and logarithmically dependent on the fatigue life.
- Effect of process parameters on the morphological and mechanical properties of 3D Bioextruded poly(ε‐caprolactone) scaffoldsPublication . Domingos, M.; Chiellini, F.; Gloria, A.; Ambrosio, L.; Bártolo, P.; Chiellini, E.Purpose – This paper aims to report a detailed study regarding the influence of process parameters on the morphological/mechanical properties of poly(1-caprolactone) (PCL) scaffolds manufactured by using a novel extrusion-based system that is called BioExtruder. Design/methodology/approach – In this study the authors focused investigations on four parameters, namely the liquefier temperature (LT), screw rotation velocity (SRV), deposition velocity (DV) and slice thickness (ST). Scaffolds were fabricated by employing three different values of each parameter. Through a series of trials, scaffolds were manufactured varying iteratively one parameter while maintaining constant the other ones. The morphology of the structures was investigated using a scanning electron microscope (SEM), whilst the mechanical performance was assessed though compression tests. Findings – Experimental results highlight a direct influence of the process parameters on the PCL scaffolds properties. In particular, DV and SRV have the highest influence in terms of road width (RW) and consequently on the porosity and mechanical behaviour of the structures. Research limitations/implications – The effect of process and design parameters on the biological response of scaffolds is currently under investigation. Originality/value – The output of this work provides a major insight into the effect of process parameters on the morphological/mechanical properties of PCL scaffolds. Moreover, the potential and feasibility of this novel extrusion-based system open a new opportunity to study how structural features may influence the characteristics and performances of the scaffolds, enabling the development of integrated biomechanical models that can be used in CAD systems to manufacture customized structures for tissue regeneration.
- Heatsinks to Cool Batteries for Unmanned Aerial VehiclesPublication . Galvão, J.; Faria, P.; Mateus, A.; Pereira, T.; Fernandes, S.This study aims to develop several different models of heatsinks, designed to cool a vertical take-off and landing unmanned aerial vehicle (UAV) battery, through topology optimization, aimed at being manufactured through selective laser melting (SLM) technology. A battery’s temperature must be properly managed for a safe and efficient operation. The methodology developed was with the support of software to carry out several simulations which, starting from several scenarios and restrictions imposed by the small space available to accommodate these small batteries in this type of aircraft. The conception resulted in several battery thermal management systems (BTMS) models, with different applications and efficiency degrees. A relevant aspect is the topology optimization being coupled to computational thermal analysis to reduce the mass of the heatsink whilst ensuring a maximum battery temperature threshold. Together with the use of topology optimization, the SLM process was selected to manufacture the heat sinks, under conditions of geometric freedom, using several high thermal conductivity metal alloys, such as, aluminium and copper to obtain the designed models.
- Bioactive Electrospun Fibers of Poly(ε-Caprolactone) Incorporating α-Tocopherol for Food Packaging ApplicationsPublication . Dumitriu, Raluca P.; Stoleru, Elena; Mitchell, Geoffrey R.; Vasile, Cornelia; Brebu, MihaiAntioxidant activity is an important feature for food contact materials such as packaging, aiming to preserve freshness and retard food spoilage. Common bioactive agents are highly susceptible to various forms of degradation; therefore, protection is required to maintain functionality and bioavailability. Poly(ε-caprolactone) (PCL), a biodegradable GRAS labeled polymer, was used in this study for encapsulation of α-tocopherol antioxidant, a major component of vitamin E, in the form of electrospun fibers. Rheological properties of the fiber forming solutions, which determine the electrospinning behavior, were correlated with the properties of electrospun fibers, e.g., morphology and surface properties. Interactions through hydrogen bonds were evidenced between the two components. These have strong effect on structuration of macromolecular chains, especially at low α-tocopherol amounts, decreasing viscosity and elastic modulus. Intra-molecular interactions in PCL strengthen at high α-tocopherol amounts due to decreased solvation, allowing good structural recovery after cease of mechanical stress. Morphologically homogeneous electrospun fibers were obtained, with ~6 µm average diameter. The obtained fibers were highly hydrophobic, with fast release in 95% ethanol as alternative simulant for fatty foods. This induced good in vitro antioxidant activity and significant in vivo reduction of microbial growth on cheese, as determined by respirometry. Therefore, the electrospun fibers from PCL entrapping α-tocopherol as bioactive agent showed potential use in food packaging materials.
- Processing and Characterization of 3D Dense Chitosan Pieces, for Orthopedic Applications, by Adding PlasticizersPublication . Figueiredo, Lígia; Moura, Carla; Pinto, Luís F.V.; Ferreira, Frederico Castelo; Rodrigues, AlexandraIn this work, plasticizer agents were incorporated in a chitosan based formulation, as a strategy to improve the fragile structure of chitosan based-materials. Three different plasticizers: ethylene glycol, glycerol and sorbitol, were blended with chitosan to prepare 3D dense chitosan specimens. The properties of the obtained structures were assessed for mechanical, microstructural, physical and biocompatibility behavior. The results obtained revealed that from the different specimens prepared, the blend of chitosan with glycerol has superior mechanical properties and good biological behavior, making this chitosan based formulation a good candidate to improve robust chitosan structures for the construction of bioabsorbable orthopedic implants.
- BioCell Printing : Integrated automated assembly system for tissue engineering constructsPublication . Bártolo, P.; Domingos, M.; Gloria, A.; Ciurana, J.The production methodology of 3D constructs for tissue regeneration is usually a complex discontinuous process involving three different stages: (1) production of 3D matrices; (2) matrix sterilisation and cell seeding; (3) in vitro dynamic cell culture. This paper presents a novel automated bench-top manufacturing system called BioCell Printing, designed for the integrated, continuous and fully automated production and in vitro dynamic culture of tissue engineering constructs. The BioCell aims at the rapid production of tissue-engineered substitutes with low risk of contamination, increasing the chances of direct clinical application.
- Optimisation of Alginate Extraction and Characterisation of Polysaccharides from Brown Seaweed from the Portuguese CoastPublication . Mendes, Joana Corrêa; Valente, Joana F. A.; Sousa, Fani; Bernardino, Raul; Bernardino, Susana; Afonso, Clélia; Chagas, BárbaraAlginate is a widely used and versatile biopolymer with an ever-expanding range of applications in the pharmaceutical and biomedical industries. This highlights the importance of developing sustainable and renewable production sources. Conventional extraction methods, although effective, are often energy-intensive and rely on harsh chemicals. In this context, brown algae are a promising alternative due to their abundance and renewability. This study investigated the potential of Saccorhiza polyschides and Sargassum muticum as sources of sodium alginate (SA), thus optimising an extraction process that combines acid treatment with an alkaline step. The extracted biopolymers were characterised using FTIR, H-NMR, STA, SEM/EDX, viscosity measurements, dynamic light scattering, and spectrophotometric assays of residual polyphenols and proteins. The optimised extraction conditions produced yields above 20% of high-purity alginate. When compared with commercial SA, the extracted materials showed comparable quality while relying on a simplified, solvent-reduced protocol that improves process efficiency and reduces the environmental impact. These results demonstrate that S. polyschides and S. muticum are promising, locally available sources of high-quality sodium alginate, and that industrially relevant yields (>20%) can be achieved through an environmentally conscious two-step extraction process.