• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.4
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• pp.417-424
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• 2009

A micro-mixer with a quasi-active rotor was fabricated, and mixing characteristics were evaluated. The proposed micro-mixer combines an active type micro-mixer with a passive type micro-mixer. The micro-rotor, which is a moving part of an active type micro-mixer, is added in a micro-chamber of a passive type vortex micro-mixer. The rotor rotated by inflows tangent to a chamber, causing strong perturbations. The micro-mixers were fabricated using photosensitive glass. Mixing efficiency of the micro-mixers was measured using an image analysis method. Mixing efficiency and characteristics of the micro-rotor mixer were compared with the vortex micro-mixer without a rotor. Mixing efficiency was reduced as Reynolds number increased at a low Reynolds number due to decrease of residence time. Mixing efficiency at higher Reynolds number, on the other hand, was improved even though residence time decreased since the contact surface between fluids increased by twisted flow. The perturbation induced by rotating rotor at greater than Re 200 improved the efficiency of the rotor mixer.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.233-236
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• 2003

The micro-stereolithography technology made it possible to fabricate a freeform 3D micro-structure. Using this technology, two kind of applications were fabricated and tested: micro-lens and micro-mixers. The focal length and f-number of the micro-lens were 5 mm and 2.5, respectively. The focusing ability of the micro-lens was verified by defocusing the He-Ne laser beam after passing the lens. Two mixers are Kenics micro-mixer and BEKM. BEKM is a modified Kenics micro-mixer by introducing barriers on the pipe walt periodically to enhance the mixing via the chaotic mechanism in the helical flow of Kenics micro-mixer. Experimental result shows good mixing performance of developed mixers. Especially, the BEKM shows better mixing performance then Kenics micro-mixer.

• 한국가시화정보학회:학술대회논문집
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• 2005.12a
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• pp.99-102
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• 2005

This study was conducted for obtaining the optimized data to build the mixer or micro fluid device as measuring the three dimensions flow field in micro mixer. To acquire the rapid diffusion on the region of low Reynolds (Re < 100), the staggered herringbone mixer using chaotic advection was selected in this case. At first, by conducting the numerical analytical virtual experiment using CFD-ACE+, three dimensions flow field in the micro mixer was estimated As this flow field was proven using defocusing particle tracing method, the behavior of micro flow with three dimensional aspects could be analyzed. Numerical analysis and flow pattern in the micro mixer by experimental verification made to be able to analyze the chaotic advection. These can be important sources for building more optimized form. Verifying the information of three dimensional flow structure, these information can be used as the data for developing and improving the $\mu$ -TAS.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.166-171
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• 2004

In this study, shape optimization of micro-static mixer with a cantilever beam was accomplished for mixing the mixing efficiency by using successive response surface approximations. Variables were chosen as the length of cantilever beam and the angle between horizontal and the cantilever beam. Sequential approximate optimization method was used to deal with both highly nonlinear and non-smooth characteristics of flow field in a micro-static mixer. Shape optimization problem of a micro-static mixer can be divided into a series of simple subproblems. Approximation to solve the subproblems was performed by response surface approximation, which does not require the sensitivity analysis. To verify the reliability of approximated objective function and the accuracy of it, ANOVA analysis and variables selection method were implemented, respectively. It was verified that successive response surface approximation worked very well and the mixing efficiency was improved very much comparing with the initial shape of a micro-static mixer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1642-1648
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• 2006

This paper describes enhancement of the mixing efficiency of a multilamination micro mixer by adding a number of recirculation zones downstream of the mixing zone. Numerical simulation was employed to estimate the mixing efficiency and the pressure drop under various conditions. Numerical results indicated that recirculation micro mixer brought about not only the increase of the mixing efficiency but also the decrease of the pressure drop. Micro mixers were fabricated using photosensitive glass by anisotropic wet etching technique. The width and height of the micro channel were $150{\mu}m$ and $500{\mu}m$, respectively. The performance of micro mixer was measured using color intensity variation of the fluid. Except for extremely low Re below 40, the recirculation micro mixer of the present study showed improved mixing. And the enhancement of the mixing increased as Re rose. When Re increased beyond 400, more than 90% of the mixing was observed in the experiment.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.6
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• pp.143-149
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• 2008

This paper presents the results of the study on the novel micro mixer. Existing micro mixer is classified as active mixing and passive mixing by the mixing principles. Both mixing principles have problems. For solving these problems, this research has developed the novel micro mixers based on a totally different principle compared with former mixers. They not only have a simpler structure than former ones but also are able to achieve high mixing efficiency in spite of low power consumption due to using Lorentz Force. In addition, they are designed to increase the efficiency of mixing by changing the rotating direction of fluid with a polar switching circuit. Driving forces of the mixer are Lorentz force and a moving force of fluid due to electrophoresis. Because the efficiency of mixer is affected by electrode shape, several models have been made. The computer simulation has been made to estimate the efficiency of each mixer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.9
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• pp.1314-1319
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• 2004

In this study, parameter optimization of micro-static mixer with a cantilever beam was accomplished for maximizing the mixing efficiency by using successive response surface approximations. Variables were chosen as the length of cantilever beam and the angle between horizontal and the cantilever beam. Sequential approximate optimization method was used to deal with both highly nonlinear and non-smooth characteristics of flow field in a micro-static mixer. Shape optimization problem of a micro-static mixer can be divided into a series of simple subproblems. Approximation to solve the subproblems was performed by response surface approximation, which does not require the sensitivity analysis. To verify the reliability of approximated objective function and the accuracy of it, ANOVA analysis and variables selection method were implemented, respectively. It was verified that successive response surface approximation worked very well and the mixing efficiency was improved very much comparing with the initial shape of a micro-static mixer.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.5
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• pp.95-100
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• 2008

An active micro-mixer, which is composed of an oscillating micro-stirrer in the micro-channel to provide effective mixing was optimized. The effects of molecular diffusion and disturbance by the stirrer were considered with regard to two types of mixer models: the simple straight micro-channel and micro-channel with an oscillating stirrer. Two types of mixer models were studied by analyzing mixing behaviors such as their interaction after the stirrer. The mixing was calculated by Lattice Boltzmann methods using the D2Q9 model. In this study, the time-averaged mixing index formula was used to estimate the mixing performance of time-dependent flow. The mixing indices of the two models were compared. From the results, it was found that the mixer with an oscillating stirrer was much more enhanced and stabilized. Therefore, an approximate optimization of an active micro-mixer with an oscillating stirrer was performed using Kriging method with OLHD(Optimal Latin Hypercube Design) in order to determine the optimal design variables. The design parameters were established as the frequency, the length and the angle of the stirrer. The optimal values were obtained as 1.0346, 0.66D and $\pm45^{\circ}$, respectively. It was found that the mixing index of the optimal design increased by 88.72% compared with that of the original design.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.539-540
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• 2006

It is so difficult to small amounts of two or more fluid species into single in microchannel because flows are usually laminar. In this regard multilamination micro mixer including recirculation zone is presented. Alternating feed micro channels make multilamination and converging-diverging channels form recirculation zone. Multilamination with geometric focusing decreases diffusion path ana recirculation zones make vortex. In this paper flow patterns and mixing properties of multilamination micro mixer including recirculation zone were investigated by Computational Fluid Dynamics (CFD). The CFD results provided qualitative information on mixing.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.275-281
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• 2005

In this work, Scalar Passive code in Lattice Boltzmann Method was employed to simulate mixing performance of Passive mixer in a micro-channel. It physically analyzed stream line and Pressure drop for passive mixer in a micro-channel. The flow characteristics in a micro-channel was a function of Peclet number. The results indicated that the size of static element was more effect on the mixing than the number of static element and the distance of static elements.