A design methodology for micromixers is presented which systematically integrates computational fluid dynamics (CFD) with an optimization methodology based on the use of design of experiments (DOE), function approximation technique (FA) and multi-objective genetic algorithm (MOGA). The methodology allows the simultaneous investigation of the effect of geometric parameters on the mixing performance of micromixers whose design strategy is based fundamentally on the generation of chaotic advection. The methodology has been applied on a Staggered Herringbone Micromixer (SHM) at several Reynolds numbers. The geometric features of the SHM are optimized and their effects on mixing are evaluated. The degree of mixing and the pressure drop are the performance criteria to define the efficiency of the micromixer for different design requirements

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A 3-D configuration of a T-mixer is evaluated under normal operating conditions of the called convective micromixers. The design has been called 3-D T-mixer in our previous work [1] as it adopts a three-dimensional structure at the T-junction. This design feature has been found that it exerts a strong effect on the flow characteristics in the device downstream in the mixing channel. A numerical study has been carried out in the 3-D T-mixer and the typical T-mixer, being these modelled with equal dimensions of channel lengths and cross sections and operated with the same flow rates. The flow analysis in the 3-D T-mixer reveals the quick formation of vortical flow structures composed of intertwined fluid filaments which increase drastically the fluids interface to enhance mixing. The flow patterns in the mixing channel vary with Reynolds number (Re) in the range 100-500. This study shows that the 3-D T-mixer provides a significant enhancement of mixing and presents lower pressure loss and similar level of shear stress compared to a typical T-mixer, in the whole range of Re used to characterize the flow. It has a simple channel configuration which is easy to fabricate and effective for mixing of continuous fluid and potentially particles. The 3-D T-mixer is called to be tested and applied for improving the efficiency of systems which have a T-junction in their design and require fast mixing with high throughput

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Numerical simulations and experiments are used to evaluate the flow and mixing characteristics of a proposed convective 3-D T-type micromixer. The study presents a parametric study and performance optimization of this micromixer based on the variation of its geometry. To investigate the effect of design and operation parameters on the device performance, a systematic design and optimization methodology is applied; it combines Computational Fluid Dynamics (CFD) with an optimization strategy that integrates Design of Experiments (DOE), Surrogate modeling (SM) and Multi-Objective Genetic Algorithm (MOGA) techniques. The degree of mixing and the pressure loss in the mixing channel are the performance criteria to identify optimum designs at different Reynolds numbers (Re). The convective flow generated in the 3-D T-type micromixer drastically enhances mixing at Re > 100 by making the two fluids to roll up along the mixing channel. The resulting optimum designs are fabricated on polymethylmethacrylate (PMMA) by CNC micromachining. Experiments are carried out to visualize the streams of de-ionized water and aqueous fluorescein solution, by which the extent of mixing is determined, based on the standard deviation of fluorescein intensities on cross-section images. This study applies a systematic procedure for evaluation and optimization of a proposed 3-D T-mixer which has a configuration of channels that promote convective mixing since the two fluids come into contact. The methodology applied can also be used to efficiently modify and customize current micromixers.

The general design rules indicate that when identical macroscale pumps (each with a maximum flowrate Q m , and maximum pressure drop P max ) are combined in series, the maximum flowrate is Q m , but the maximum pressure drop becomes 2 P max , while combined in parallel the maximum flowrate becomes 2Q m , and the maximum pressure is P max . In this paper, we test whether these design rules apply to microscale valveless micropumps using highly resolved CFD calculations. The variation of flow with pump pressure drop is studied by varying the resistance of an external circuit. The analysis confirmed that the macroscale design rules for macroscale pumps are applicable to microscale pumps. The study also enabled the influence of different forcing strategies on the pump performance to be analyzed.[2012-0208]

Numerical simulations and an optimization method are used to study the design of a planar T-micromixer with curved-shaped baffles in the mixing channel. The mixing efficiency and the pressure loss in the mixing channel have been evaluated for Reynolds number (Re) in the mixing channel in the range 1 to 250. A Mixing index (Mi) has been defined to quantify the mixing efficiency. Three geometric dimensions: radius of baffle, baffles pitch and height of the channel, are taken as design parameters, whereas the mixing index at the outlet section and the pressure loss in the mixing channel are the performance parameters used to optimize the micromixer geometry. To investigate the effect of design and operation parameters on the device performance, a systematic design and optimization methodology is applied, which combines Computational Fluid Dynamics (CFD) with an optimization strategy that integrates Design of Experiments (DOE), Surrogate modeling (SM) and Multi-Objective Genetic Algorithm (MOGA) techniques. The Pareto front of designs with the optimum trade-offs of mixing index and pressure loss is obtained for different values of Re. The micromixer can enhance mixing using the mechanisms of diffusion (lower Re) and convection (higher Re) to achieve values over 90%, in particular for Re in the order of 100 that has been found the cost-effective level for volume flow. This study applies a systematic procedure for evaluation and optimization of a planar T-mixer with baffles in the channel that promote transversal 3-D flow as well as recirculation secondary flows that enhance mixing.