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Abstract(s)
Este projeto de mestrado em Tecnologia Biomédica, de natureza essencialmente experimental, foi desenvolvido no Instituto Politécnico de Bragança (IPB) e na Universidade de Extremadura, Espanha.
Foram dois os objetivos principais do trabalho realizado: um consistiu em estudar a formação e o transporte de microbolhas capazes de gerar embolias gasosas, desenvolvido no IPB, outro consistiu na fabricação e estudo do comportamento de micropartículas de polidimetilsiloxano (PDMS), que simulam os glóbulos vermelhos, através de uma técnica desenvolvida na Universidade de Extremadura, designada por focagem de fluxo.
Para realizar o escoamento das microbolhas, foram fabricados pelo método de xurografia, microdispositivos de focagem de fluxo. Efetuaram-se escoamentos bifásicos de Dextrano (Dx40) com 2,5% hematócrito (Hct) e ar, a vários caudais. Nestes escoamentos foi possível visualizar a formação de microbolhas na zona de contração do microcanal. Foram analisados vários parâmetros: dimensão das bolhas, distância entre pares de bolhas, índice de deformação, velocidade das bolhas e espessura da camada livre de células em três zonas do microcanal.
O estudo das microbolhas ao longo dos vasos sanguíneos, torna-se relevante visto que podem obstruir estes vasos e assim promover a deterioração dos tecidos e, em determinados casos, causar a morte dos mesmos.
Na técnica de focagem de fluxo, utilizou-se polidimetilsiloxano (PDMS), glicerina e surfactante Brij 30, o que permitiu a produção de microgotas de PDMS com diâmetros entre os 10 e 11 μm. Após um processo de cura, obtiveram-se micropartículas com diâmetros inferiores, na ordem dos 4,4 μm. Foi analisado o índice de deformação médio das micropartículas em glicerina e Brij 30, e dos glóbulos vermelhos em Dx40, num canal com uma contração hiperbólica. Este trabalho possibilitou, pela primeira vez, a produção de micropartículas com diâmetros próximos dos glóbulos vermelhos (GVs).Estas micropartículas podem vir a ser utilizadas na produção de fluidos análogos ao sangue, simulando os GVs. Os fluidos análogos ao sangue são cada vez mais relevantes nos estudos in vitro. A utilização destes fluidos permite ultrapassar questões de natureza ética e de segurança.
This master's project in Biomedical Technology, was developed at the Polytechnic Institute of Bragança (IPB) and at the University of Extremadura, Spain. This research work has two main objectives: to study the formation and transport of microbubbles capable of generating air embolism (work performed in IPB) and to fabricate and study the behaviour of microparticles of polydimethylsiloxane (PDMS), which simulate the red blood cells, through a technique developed at the University of Extremadura known as flow focusing. By using the xurography method, microchannels with a flow focusing geometries were fabricated. A two phase fluid flow having Dx40 with 2.5% Hct and air, was tested at various flow rates. At the tested flows it was possible to visualize the formation of microbubbles at the contraction region of the microchannel. In this study, several parameters were analysed such as dimension of the bubbles, the distance between pairs of bubbles, deformation index, velocity of the bubbles and the thickness of the cell free layer in three different zones of microchannel, i. e., contraction, intermediate and expansion zone. The study of microbubbles along the blood vessels, became relevant as it may obstruct the vessels thereby promoting deterioration of the tissues and, in certain cases, cause the death thereof. By means of a flow focusing technique, PDMS, glycerine and surfactant Brij 30 was used to produce PDMS droplets with diameters between 10 and 11 μm. However, after the curing process, microparticles with lower diameters of about 4 μm were obtained. It was also analysed the average deformation index of the microparticles in glycerine and Brij 30, and red blood cells (RBCs) in Dx40, flowing in a microchannel having a hyperbolic contraction. Hence, for the first time. Generated microdroplets had diameters dimensions close to RBCs. These generated microparticles can simulate RBCs and produce blood analogous fluids. The blood analogous fluids are increasingly important in vitro blood studies as the use of these fluids can overcomes both ethical and safety issues.
This master's project in Biomedical Technology, was developed at the Polytechnic Institute of Bragança (IPB) and at the University of Extremadura, Spain. This research work has two main objectives: to study the formation and transport of microbubbles capable of generating air embolism (work performed in IPB) and to fabricate and study the behaviour of microparticles of polydimethylsiloxane (PDMS), which simulate the red blood cells, through a technique developed at the University of Extremadura known as flow focusing. By using the xurography method, microchannels with a flow focusing geometries were fabricated. A two phase fluid flow having Dx40 with 2.5% Hct and air, was tested at various flow rates. At the tested flows it was possible to visualize the formation of microbubbles at the contraction region of the microchannel. In this study, several parameters were analysed such as dimension of the bubbles, the distance between pairs of bubbles, deformation index, velocity of the bubbles and the thickness of the cell free layer in three different zones of microchannel, i. e., contraction, intermediate and expansion zone. The study of microbubbles along the blood vessels, became relevant as it may obstruct the vessels thereby promoting deterioration of the tissues and, in certain cases, cause the death thereof. By means of a flow focusing technique, PDMS, glycerine and surfactant Brij 30 was used to produce PDMS droplets with diameters between 10 and 11 μm. However, after the curing process, microparticles with lower diameters of about 4 μm were obtained. It was also analysed the average deformation index of the microparticles in glycerine and Brij 30, and red blood cells (RBCs) in Dx40, flowing in a microchannel having a hyperbolic contraction. Hence, for the first time. Generated microdroplets had diameters dimensions close to RBCs. These generated microparticles can simulate RBCs and produce blood analogous fluids. The blood analogous fluids are increasingly important in vitro blood studies as the use of these fluids can overcomes both ethical and safety issues.
Description
Keywords
Fabricação de microcanais Escoamento sanguíneo Produção de microbolhas Produção de micropartículas Técnica de focagem de fluxo