Geometrically Enhanced Flow Within Microfluidic for Homogenous Mixing (original) (raw)
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Passive mixing in microchannels by applying geometric variations
Passive mixing by applying geometric variations were studied in this research. In respect to the nature of laminar flow in a microchannel, the geometric variations were designed to try to improve the lateral convection. By doing this, the dispersion of solute was not only contributed by diffusion, but also, and more importantly, the convection in the lateral direction. Geometric parameters versus the mixing performance were investigated systematically in T-type channels, by applying a known computational fluidic dynamic (CFD) solver for microfluidics. Various obstacle shapes, sizes and layouts were studied. As the ratio of the height of obstacles to the depth of channel became negative, it was the special case that obstacles became grooves. The mechanism for obstacles to enhance mixing was to create convective effects. However, the asymmetric arrangement of grooves applied a different mechanism to enhance mixing by create helical shaped recirculation of fluids. The stretching and folding of fluids of this mixing mechanism provided a efficient way to reduce the diffusion path in microchannels. The mixing performance of mixers with obstacles were evaluated by mass fraction, and mixers with grooved surfaces were evaluated by particle tracing techniques. The results illustrated that both of the strategies provided potential solutions to microfluidic mixing.
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This study investigated micromixers formed by a T-junction and a mixing channel consisting of serial modules formed by appropriately arranging the subsections with right shifted T-shaped, left shifted T-shaped and square cross-sections. The T-shaped cross-sections are constructed by protrusions and indentations on the channel wall. The variation of shape and size of the channel cross-section may induce a strong swirl structure of flow to enhance fluid mixing. Four parameters (the lengths of the three aforementioned subsections and the sequence of modules) were selected to optimize the micromixer, and computational fluid dynamics (CFD) together with Taguchi method was applied to select the values of the parameters. Then, the micromixer was fabricated by a lithography process and the fluid mixing in the micromixer was observed by using a confocal spectral microscope imaging system. The numerical and experimental results show that the novel micromixer with the deliberately designed geometry enhances fluid mixing efficiently at relatively low Reynolds number. The effects of the four parameters on fluid mixing in the proposed micromixer are examined by CFD simulation.
Passive mixing in microchannels by applying geometric variations
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Passive mixing by applying geometric variations were studied in this research. In respect to the nature of laminar flow in a microchannel, the geometric variations were designed to try to improve the lateral convection. By doing this, the dispersion of solute was not only contributed by diffusion, but also, and more importantly, the convection in the lateral direction. Geometric parameters versus the mixing performance were investigated systematically in T-type channels, by applying a known computational fluidic dynamic (CFD) solver for microfluidics. Various obstacle shapes, sizes and layouts were studied. As the ratio of the height of obstacles to the depth of channel became negative, it was the special case that obstacles became grooves. The mechanism for obstacles to enhance mixing was to create convective effects. However, the asymmetric arrangement of grooves applied a different mechanism to enhance mixing by create helical shaped recirculation of fluids. The stretching and folding of fluids of this mixing mechanism provided a efficient way to reduce the diffusion path in microchannels. The mixing performance of mixers with obstacles were evaluated by mass fraction, and mixers with grooved surfaces were evaluated by particle tracing techniques. The results illustrated that both of the strategies provided potential solutions to microfluidic mixing.
The Effect of Fluid Viscosity in T-shaped Micromixers
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Micromixing technology has experienced rapid development in the past few years. Micromixers represent one of the essential components in integrated microfluidic systems for chemical, biological and medical applications In general, macro-scale mixing is achieved with turbulence while mixing in micro-scale is done by diffusion. This is due to low Reynolds number i.e laminar behavior of the flow in micro channels. Micro-mixer with obstacles located on the channel wall as well as waveform configurations are used to enhance mixing in the channel, so as to reduce the mixing length. Micro channels with different geometric layout and with different shapes and sizes of obstacles such as rectangular, triangular and semicircular enhance their mixing length. The triangular obstacles within the T as well as Y channel gave minimum mixing length for the same distance between the obstacles. The commercial computational fluid dynamics tool for micro-fluidics, known as Comsol multyphysics, is used to study the effect of different configuration on pressure drop as well as to study the mixing of two fluids in different configurations. Computational fluid dynamics (CFD) is often used to rigorously examine the influence of the shape of microchannels on mass transport phenomena in the flow field. Fabrication of micro channels is done on PDMS and Photochemical Machining. The fabrication of microfluidic by PDMS is easier and more flexible than in silicon or glass. The use of PDMS as a material reduces the time, complexity, and cost of prototyping. It is observed that mixing length required for Plain channel without obstacle is more than channel with obstacles. Because due to obstacles, turbulence is created at tip of obstacles which increases mixing rate.
Mixing of Liquids Using Obstacles In Microchannels
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Experimental mixing characterization of Newtonian fluids mixing in asymmetric T-micromixers
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Mixing in microfluidics represents a challenge to the scientific community due to the difficulty in promoting turbulent flows, which have high mixture capacity. Therefore, three T-shaped micromixers, with asymmetric inlets of 19, 36 and 70% were manufactured in order to evaluate their mixing capacity. The manufacturing procedures were based on softlithography using two fundamental materials: the photoresist resin to build the mold and sn optically transparent polymer, which constitutes the microchannels chips. From the tests made to the three manufactured channels, with Re values in the outlet ranging between 50 and 310, five different regimes were identified. After that, the flow was evaluated in terms of mixture efficiency through the channel by two different parameters: the first one represents the segregation index of the flow and the second quantifies the diffuse mixture potential after passing through the T-junction. The study concluded that the increase on the channels geomet...