Browsing by Author "Lima, Rui A."
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- 2nd. International Workshop on Additive Manufacturing and Sustainability (IWAM): book of proceedingsPublication . Rocha, João; Ribeiro, J.E.; Santos, Jorge; Lima, Rui A.In recent years, the manufacturing processes have undergone a profound transformation, driven by the rapid evolution of additive manufacturing (AM) technologies. What began as a tool primarily for prototyping through stereolithography has now expanded into a versatile and innovative field capable of producing functional, end-use components across a wide range of industries. From fused deposition modeling (FDM) to selective laser melting (SLM) and beyond, AM has unlocked new possibilities in design, material utilization, and production efficiency. Today, additive manufacturing encompasses an extensive array of materials, including metals, polymers, paper, and even biological tissues, enabling applications that span from the mechanical industry to the biomedical sector. One of the most compelling aspects of additive manufacturing is its potential to drive sustainability in modern production processes. Unlike traditional subtractive methods, which often generate significant material waste, AM builds components layer by layer, minimizing excess material and promoting resource efficiency. Furthermore, the ability to use eco-friendly and recyclable materials aligns with global efforts to reduce environmental impact. AM also supports the production of complex, customized parts on demand, reducing the need for large inventories and long-distance transportation, thereby lowering carbon emissions. By optimizing resource use and enabling more efficient production cycles, additive manufacturing is emerging as a cornerstone of sustainable manufacturing practices. This proceeding book arrests the latest advancements, challenges, and opportunities in the field of additive manufacturing, with a particular focus on its transformative potential and contributions to sustainability. The works presented here reflect the interdisciplinary nature of AM, showcasing innovative techniques, materials, and applications that are shaping the future of manufacturing. From cutting-edge research to real-world case studies, this collection aims to inspire further exploration and collaboration, driving the adoption of additive manufacturing as a key enabler of sustainable industrial progress. We invite readers to probe into these pages and discover how AM is not only redefining manufacturing but also paving the way for a more sustainable and efficient future.
- 3D manufacturing of intracranial aneurysm biomodels for flow visualizations: low cost fabrication processesPublication . Souza, Andrews Victor Almeida; Souza, Mauren S.; Pinho, Diana; Agujetas, Rafael; Ferrera, Conrado; Lima, Rui A.; Puga, Hélder Fernandes; Ribeiro, J.E.There is a continuous search for better and more complete in vitro models with mechanical properties closer to in vivo conditions. In this work a manufacturing process, based on a lost core casting technique, is herein reported to produce aneurysm biomodels to perform experimental hemodynamic studies. By us- ing real artery images combined with a lost core casting technique, three materials were tested: paraffin, beeswax and glycerin-based soap. All in vitro biomodels were compared according to their transparency and final structure. Additionally, comparisons between experimental and numerical flow studies were also performed. The results have shown that the biomodels produced with beeswax and glycerine-based soap were the most suitable in vitro models to perform direct flow visualizations of particulate blood analogue fluids. The biomodels proposed in this works, have the potential to provide further insights into the complex blood flow phenomena happening at different kinds of pathologies and answer to important hemodynamics questions that otherwise cannot be tackled with the existing in vitro models.
- Additive manufacturing techniques for the fabrication of intracranial aneurysm biomodelsPublication . Rodrigues, D.; Souza, A.; Souza, Maria Sabrina; Ferrera, Conrado; Ribeiro, J.E.; Lima, Rui A.The hemodynamics of intracranial aneurysm (IA) involves complex phenomena that influence its growth and rupture. The advancement of additive manufacturing techniques allowed the development of biomodels suitable for in vitro experimental tests. Thus, we present in this work the process of manufacturing flow biomodels, using different additive manufacturing techniques and materials. The biomodels obtained through these methods proved to be suitable for experiments using imaging techniques and for the validation of numerical studies.
- Advances in Microfluidic Systems and Numerical Modeling in Biomedical Applications: A ReviewPublication . Ferreira, Mariana; Carvalho, Violeta Meneses; Ribeiro, J.E.; Lima, Rui A.; Teixeira, Senhorinha F.C.F.; Pinho, DianaThe evolution in the biomedical engineering field boosts innovative technologies, with microfluidic systems standing out as transformative tools in disease diagnosis, treatment, and monitoring. Numerical simulation has emerged as a tool of increasing importance for better understanding and predicting fluid-flow behavior in microscale devices. This review explores fabrication techniques and common materials of microfluidic devices, focusing on soft lithography and additive manufacturing. Microfluidic systems applications, including nucleic acid amplification and protein synthesis, as well as point-of-care diagnostics, DNA analysis, cell cultures, and organ-on-a-chip models (e.g., lung-, brain-, liver-, and tumor-on-a-chip), are discussed. Recent studies have applied computational tools such as ANSYS Fluent 2024 software to numerically simulate the flow behavior. Outside of the study cases, this work reports fundamental aspects of microfluidic simulations, including fluid flow, mass transport, mixing, and diffusion, and highlights the emergent field of organ-on-a-chip simulations. Additionally, it takes into account the application of geometries to improve the mixing of samples, as well as surface wettability modification. In conclusion, the present review summarizes the most relevant contributions of microfluidic systems and their numerical modeling to biomedical engineering.
- An automatic method to track red blood cells in microchannelsPublication . Pinho, Diana; Gayubo, Fernando; Pereira, Ana I.; Lima, Rui A.Image analysis is extremely important to obtain crucial information about the blood phenomena in micro-circulation. The current study proposes an automatic method for segmentation and tracking red blood cells (RBCs) flowing through a 100 μm Glass capillary. The original images were obtained by means of a confocal system and then processed in Matlab using the Image Processing Toolbox. The automatic measurements ob-tained with the proposed automatic method are compared with a manual tracking method using a plugin from ImageJ.
- An effective thermal technology for the detoxification of the MSW fly ashPublication . Lima, Rui A.; Saloca, MarcosThe increasing public concern of potential health problems, due to improper waste disposal practices as well as the introduction of landfill taxes, have induced the practice of incineration. Presently, all UK incinerators have to meet very strict emission levels. In this way, the generated fly ash residues have to be managed very carefully as they are enriched with toxic organic micropollutants and heavy metals. The aim of the present work is to describe a novel thermal technology, known as the ash detoxification process, that has shown success not only in the destruction of its toxic organic components, but also in the fixation of its heavy metal content to form an unleachable material.
- An in vitro experimental evaluation of the displacement field in an intracranial aneurysm modelPublication . Pinho, Diana; Bento, David; Ribeiro, J.E.; Lima, Rui A.; Vaz, M.A.P.The purpose of this paper is to develop a system able to study experimentally the displace-ment field of an in vitro intracranial aneurysm. Origin and growth of aneurysms is the result of a complex interaction between biological processes in the arterial wall and the involved hemo-dynamic phenomena’s. Once the aneurysm forms, the repetitive pressure and shear stresses exerted by the blood flow on the debilitated arterial wall can cause a gradual expansion. One promising method to evaluate and measure this expansion is to use optical field experimental techniques, such as interferometry. In this work the Electronic Speckle Pattern Interferometry was used to evaluate the deformation occurred on an intracranial aneurysm model fabricated in polydimensiloxane (PDMS) by using a 3D printer combined with a soft lithography tech-nique.
- Análise do escoamento sanguíneo em microcanais com bifurcaçõesPublication . Cidre, Diana; Oliveira, Brigitte; Lagoela, Marco; Fernandes, Carla S.; Lima, Rui A.; Dias, Ricardo P.; Balsa, Carlos; Ishikawa, Takuji; Yamaguchi, TakamiVários estudos revelaram que a informação obtida sobre as propriedades reológicas do sangue em capilares de vidro difere da situação in vivo (Pries et al. 1994). As principais causas potenciais para estas discrepâncias podem ser devidas à camada superficial formada por células endoteliais e às redes microvasculares compostas por segmentos de vasos irregulares e curtos que estão ligados por numerosas bifurcações e convergências (Maeda 1996).O principal objectivo deste trabalho é analisar as propriedades não-Newtonianas do sangue durante o escoamento em modelos microvasculares. Neste estudo foi utilizado o método de litografia suave para fabricar microcanais bifurcados com secção rectangular em polidimetisiloxano (PDMS). Usando um sistema “confocal micro-PTV” (Lima et al. 2008), mediu-se o efeito da bifurcação no escoamento de partículas fluorescentes diluídas em água pura e em suspensões concentradas de eritrócitos. Os resultados experimentais obtidos pelo sistema “confocal micro-PTV” foram complementados por modelos hemodinâmicos computacionais. Após a execução de várias simulações com o software comercial de elementos finitos POLYFLOW®, compararam-se alguns resultados experimentais com resultados numéricos. Os resultados preliminares sugerem que as trajectórias dos eritrócitos podem sofrer alterações na direcção transversal ao escoamento devido à colisão com os eritrócitos que se encontram na vizinhança do ponto de divergência da bifurcação (Brigitte et al. 2009).
- Análise do escoamento sanguíneo em microcanais com bifurcaçõesPublication . Cidre, Diana; Lagoela, Marco; Oliveira, Brigitte; Fernandes, Carla S.; Balsa, Carlos; Lima, Rui A.; Dias, Ricardo P.; Ishikawa, Takuji; Yamaguchi, TakamiA dinâmica do escoamento sanguíneo na microcirculação depende fortemente das redes microvasculares compostas por segmentos de vasos curtos irregulares que estão ligados por inúmeras bifurcações. Este trabalho apresenta a aplicação de um sistema micro-PTV confocal para medir o comportamento dos eritrócitos durante o escoamento em um microcanal polidimetisiloxano (PDMS) rectangular com uma bifurcação. O efeito da bifurcação no escoamento de partículas fluorescentes diluídas em água pura e em suspensões concentradas com eritrócitos foi medido através de um sistema micro-PTV confocal. Numericamente, estudou-se o escoamento do sangue recorrendo ao software comercial de elementos finitos POLYFLOW® utilizando diferentes modelos reológicos. Os resultados preliminares sugerem que as trajectórias dos eritrócitos podem sofrer alterações na direcção transversal devido à acumulação de eritrócitos na vizinhança do ponto de divergência da bifurcação.
- Analysis of a vegetable oil performance in a milling process by MQL lubricationPublication . Afonso, Inês Santos; Pereira, J.A.; Ribeiro, António E.; Amaral, Joana S.; Rodrigues, Nuno; Gomes, José R.; Lima, Rui A.; Ribeiro, J.E.In this work, we carried out a comparison between the dry machining of an aluminum block with conventional cutting oil and a block with vegetable oil. The two oils had different flow rates. Using the Taguchi method, it was possible to determine the matrices for optimizing the best parameters for each group of tests. Then, we studied the utility of using vegetable oil as a cutting lubricant. We found that the vegetable oil studied in this work had good properties in terms of reducing cutting temperatures but was less effective than conventional cutting oil in reducing the surface roughness of the machined part. Tribological tests were carried out to understand the influence of the selected lubricants in reducing friction and wear. After the sliding experiments, which were performed without lubrication in the presence of the same lubricants that were used in the machining tests and in the presence of distilled water, we concluded that vegetable oil has satisfactory lubricating properties that are similar to those of the conventional cutting fluid, indicating a potential for consideration as an effective alternative to the conventional cutting fluid, with economic, environmental, and health advantages.