Evaluation of flow characteristics that give higher mixing performance in the 3-D T-mixer versus the typical T-mixer

This document is the Accepted Manuscript of the following article: Cesar Augusto Cortes-Quiroz, Alireza Azarbadegan, and Mehrdad Zangeneh, ‘Evaluation of flow characteristics that give higher mixing performance in the 3-D T-mixer versus the typical T-mixer’, Sensors and Actuators B: Chemical, Vol. 202: 1209-1219, October 2014, DOI: https://doi.org/10.1016/j.snb.2014.06.042, made available under the the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License CC BY NC-ND 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/).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.Peer reviewedFinal Accepted Versio

Analysis and design optimization of an integrated micropump-micromixer operated for bio-MEMS applications

A generic microfluidic system composed by two single chamber valveless micropumps connected to a simple T-type channel intersection is examined numerically. The characteristics of a feasible valveless micropump have been used in the design, where efficient mixing is produced due to the pulsating flow generated by the micropumps. The advantages of using time pulsing inlet flows for enhancing mixing in channels have been harnessed through the activation of intrinsic characteristics of the pumps required to achieve the periodic flows. A parametric study is carried out on this microfluidic system using Computational Fluids Dynamics (CFD) on a design space defined by a Design-of-Experiments (DOE) technique. With this approach, the frequency f and the phase difference of the periodic fluid velocities (operation parameters) and the angle formed by the inlet channels at the intersection (geometric parameter) are used as design parameters, whereas mixing quality, pressure drop and maximum shear strain rate in the channel are the performance parameters. The study identifies design features for which the pressure drop and shear strain in the channel are reduced whereas the mixing quality is increased. The proposed microfluidic system achieves high mixing quality with performance parameters that enable manipulation of biological fluids in microchannels.Peer reviewedFinal Accepted Versio

An integrated silicon sensor with microfluidic chip for monitoring potassium and pH

We present ion-sensitive field effect transistor-based sensors, integrated with a microfluidic chip, for monitoring pH and potassium cations. The sensor is strategically located at the base of a well so that the response time of the device depends both on the mean flow through the device and the diffusion coefficient of the analyte being monitored. This would enable monitoring of ions in the presence of larger molecules. The dependence of the device response time on diffusive transport of analytes was examined through a numerical study of the flow field and the passive diffusion of a chemical species. The predicted device response time was compared with the experimental measurements and reasonable agreement found. The general dependence of device response time on geometry, flow rate, and analyte diffusion coefficient was derived. These devices can be used with biological fluids where monitoring of pH and cations provide vital information about the well-being of patients. © 2010 Springer-Verlag

Characterization and optimization of a three dimensional T-type micromixer for convective mixing enhancement with reduced pressure loss

Paper no. FEDSM-ICNMM2010-31257Numerical 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 deionized 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

Analysis and multi-criteria design optimization of geometric characteristics of grooved micromixer

Computational fluids dynamics (CFDs) and numerical optimization techniques are applied in an integrated methodology to explore the effects of different geometric characteristics on fluid mixing in a staggered herringbone micromixer (SHM). To quantify the mixing intensity in the mixer a mixing index is defined on the basis of the intensity of segregation of the mass concentration on a cross-section plane in the mixing channel. Four geometric parameters, i.e., aspect ratio of the mixing channel, ratio of groove depth to channel height, ratio of groove width to groove pitch and the asymmetry factor (offset) of groove, are the design variables initially selected for optimization, then two more parameters, i.e., angle of the groove and number of grooves per channel section, are evaluated. The whole optimization is conducted with a multi-objective approach for which the mixing index at the outlet section and the pressure drop in the mixing channel are the performance criteria used as objective functions. The Pareto front of designs with the optimum trade-off, maximum mixing index with minimum pressure drop, is obtained. (C) 2010 Elsevier B.V. All rights reserved.Peer reviewe

Analysis and optimization of a passive micromixer with curved-shaped baffles for efficient mixing with low pressure loss in continuous flow

Paper no. FEDSM-ICNMM2010-31245Numerical 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

Combination rules for multi-chamber valveless micropumps

The general design rules indicate that when identical macroscale pumps (each with a maximum flowrate Qm, and maximum pressure drop ΔPmax) are combined in series the maximum flowrate becomes Qm, but the maximum pressure is 2ΔPmax, while when combined in parallel the maximum flowrate is 2Qm, but the maximum pressure is ΔPmax. 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 was studied by varying the resistance of an external circuit. The analysis confirms that the design rules for macroscale pumps are applicable to microscale pumps. The study has also enabled the analysis of the influence of different forcing strategies on the pump performance.Peer reviewe

Analysis and design optimization of an integrated micropump-micromixer operated for bio-MEMS applications

Abstract A generic microfluidic system composed by two single chamber valveless micropumps connected to a simple T-type channel intersection is examined numerically. The characteristics of a feasible valveless micropump have been used in the design, where efficient mixing is produced due to the pulsating flow generated by the micropumps. The advantages of using time pulsing inlet flows for enhancing mixing in channels have been harnessed through the activation of intrinsic characteristics of the pumps required to achieve the periodic flows. A parametric study is carried out on this microfluidic system using Computational Fluids Dynamics (CFD) on a design space defined by a Design-of-Experiments (DOE) technique. The frequency f and the phase difference φ of the periodic fluid velocities (operation parameters) and the angle θ formed by the inlet channels at the intersection (geometric parameter) are used as design parameters, whereas mixing quality, pressure drop and maximum shear strain rate in the channel are the performance parameters. The study identifies design features for which the pressure drop and shear strain are reduced whereas the mixing quality is increased. The proposed microfluidic system achieves high mixing quality with performance parameters that enable manipulation of biological fluids in microchannels