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Abstract(s)
Os estudos relacionados com o escoamento de fluidos em microcanais têm assumido um lugar de destaque na área da biomédica, uma vez que permitem estudar o escoamento sanguíneo e algumas patologias que o afetam, tal como as embolias gasosas, evitando questões de ética. As embolias gasosas ocorrem quando bolhas gasosas circulam na corrente sanguínea e é importante o seu estudo pois as bolhas podem obstruir os vasos sanguíneos e provocar deterioração dos tecidos.
O objetivo deste trabalho é estudar o escoamento de fluidos em microcanais com bifurcações, capazes de produzirem bolhas. Para tal, fabricaram-se microcanais por litografia suave e, posteriormente, analisou-se o escoamento de fluidos Newtonianos e de sangue de ovino com 5 e 10% de hematócrito em Dextrano 40, para vários caudais e para pressões diferentes, com o auxílio de um microscópio invertido e uma câmara de alta velocidade.
Nestes escoamentos foi possível visualizar a formação das bolhas e o seu comportamento ao longo do microcanal e possibilitou a análise de várias características do escoamento: velocidade das bolhas e sua frequência, tempo entre bolhas, entupimento dos microcanais e efeito das bolhas no hematócrito.
Os resultados obtidos demonstraram que a velocidade das bolhas aumenta com o aumento do caudal e pressão utilizada, sendo que para caudais e pressões baixas os microcanais têm tendência a ficar obstruídos. Também demonstraram que as bolhas de ar modificam a concentração de células, existindo uma maior concentração de células atrás da bolha e uma menor concentração à frente da bolha.
Studies related to the fluids flow in microchannels have assumed a prominent place in the biomedical field, since they allow the study of the blood flow and some pathologies that affect it, such as gas embolism, avoiding ethical issues. Gaseous emboli occur when gaseous bubbles circulate in the bloodstream and their study is important because they can clog blood vessels and cause tissue deterioration. The aim of this work is to study fluid flows in microchannels with bifurcations, capable of producing bubbles. For this, microchannels were fabricated by soft lithography and Newtonian and sheep blood with 5 and 10% hematocrit in dextran 40 flows were analyzed for various flow rates and different pressures by using an inverted microscope, and a high-speed camera. In these flows it was possible to visualize the formation of the bubbles and their behavior along the microchannel and allowed the analysis of several parameters such as: velocity of the bubbles and their frequency, time between bubbles, microchannel clogging and the effect of the bubbles on the hematocrit. The obtained results showed that the velocity of the bubbles increases with the increase of the flow rate and pressure used, being that for low flows and low pressures the microchannels tend to clog. They also demonstrated that the passage of air bubbles influence cell concentration, with a higher concentration of cells upstream to the bubble and lower concentrations downstream to the bubble.
Studies related to the fluids flow in microchannels have assumed a prominent place in the biomedical field, since they allow the study of the blood flow and some pathologies that affect it, such as gas embolism, avoiding ethical issues. Gaseous emboli occur when gaseous bubbles circulate in the bloodstream and their study is important because they can clog blood vessels and cause tissue deterioration. The aim of this work is to study fluid flows in microchannels with bifurcations, capable of producing bubbles. For this, microchannels were fabricated by soft lithography and Newtonian and sheep blood with 5 and 10% hematocrit in dextran 40 flows were analyzed for various flow rates and different pressures by using an inverted microscope, and a high-speed camera. In these flows it was possible to visualize the formation of the bubbles and their behavior along the microchannel and allowed the analysis of several parameters such as: velocity of the bubbles and their frequency, time between bubbles, microchannel clogging and the effect of the bubbles on the hematocrit. The obtained results showed that the velocity of the bubbles increases with the increase of the flow rate and pressure used, being that for low flows and low pressures the microchannels tend to clog. They also demonstrated that the passage of air bubbles influence cell concentration, with a higher concentration of cells upstream to the bubble and lower concentrations downstream to the bubble.
Description
Curso em Parceria com a Universidade do Porto, Faculdade de Engenharia e a Universidade do Minho
Keywords
Escoamento sanguíneo Microfabricação Litografia suave Embolias gasosas Microbolhas