• Proceedings of the Korean Society of Rheology Conference
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• 2001.06a
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• pp.97-100
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• 2001

• Proceedings of the SAREK Conference
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• 2004.11a
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• pp.123-123
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• 2004

• Journal of computational fluids engineering
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• v.8 no.2
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• pp.16-23
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• 2003

A numerical study of the mixing of two fluids(pure water and a solution of glycerol in water) in a microchannel was carried out. By varying the glycerol content of the glycerol/water solution, the variation in mixing behavior with changes in the difference of the properties of the two fluids(e.g., viscosity, density, diffusivity) was investigated. The mixing phenomena were tested for three micromixers: a square mixer, a three-dimensional serpentine mixer, and a staggered herringbone mixer. The governing equations of continuity, momentum and solute mass fraction were solved numerically. To evaluate mixing performance, a criterion index of mixing of mixing uniformity was proposed. In the systems considered, the Reynolds numbers based on averaged properties were 1 and 10. For low Reynolds number (Re = 1), the mixing performance varied inversely with mass fraction of glycerol due to the dominance of molecular diffusion. The mixing performance by diffusion deteriorated due to a significant reduction in the residence time of the fluid inside the mixers.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.47-52
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• 2001

Micro-injection molding and microfluidic devices with the help of MEMS technologies including the LIGA process are expected to play important roles in. micro-system industries, in particular the bioapplication industry, in the near future. Understanding fluid flows in micro-channels is important since micro-channels are typical geometry in various microfluidic devices and mold inserts for micro-injection molding. In the present study, both experimental and numerical studies have been carried out to understand the detailed flow phenomena in micro-channel filling process. Three sets of micro-channels of different thickness were fabricated and a flow visualization system was also developed to observe the filling flow into the micro-channels. Experimental flow observations were extensively made to find the effects of channel width and thickness, and effects of surface tension and volume flow rate and so on. And a numerical analysis system has been developed to simulate the filling flow into micro-channels with the surface tension effect taken into account. Discussed are the flow visualization experimental observations along with the predictability of the numerical analysis system.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.2
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• pp.298-303
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• 2013

Magnetic abrasive polishing is one of the most promising finishing methods applicable to complex surfaces. Nevertheless this process has a low efficiency when applied to very hardened materials. For this reason, EP-MAP hybrid process was developed. EP-MAP process is expected to machine complex and hardened materials. In this research, deburring process using EP-MAP hybrid process was proposed. EP-MAP deburring process is applied to micro channel, thereby it can obtain both deburring process and polishing process. EP-MAP deburring process on the micro channel was performed. Through design of experiment method, error of height in this process according to process parameter is analyzed. When the level 1 parameter A(magnetic flux density) and level 2 parameter B(electric potential), C(working gap) and level 3 parameter D(feed rate) are applied in the deburring process using EP-MAP hybrid process, it provides optimum result of EP-MAP hybrid deburring process.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.9 s.186
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• pp.164-173
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• 2006

The cooling capacity of a micro-heat pipe is mainly governed by the magnitude of capillary pressure induced in the wick structure. For microchannel wicks, a higher capillary pressure is achievable for narrower and deeper channels. In this study, a metallic micro-heat pipe adopting high-aspect-ratio microchannel wicks is fabricated. Micromachining of high-aspect-ratio microchannels is done using the laser-induced wet etching technique in which a focused laser beam irradiates the workpiece placed in a liquid etchant along a desired channel pattern. Because of the direct writing characteristic of the laser-induced wet etching method, no mask is necessary and the fabrication procedure is relatively simple. Deep microchannels of an aspect ratio close to 10 can be readily fabricated with little heat damage of the workpiece. The laser-induced wet etching process for the fabrication of high-aspect-ratio microchannels in 0.5mm thick stainless steel foil is presented in detail. The shape and size variations of microchannels with respect to the process variables, such as laser power, scanning speed, number of scans, and etchant concentration are closely examined. Also, the fabrication of a flat micro-heat pipe based on the high-aspect-ratio microchannels is demonstrated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.2 s.245
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• pp.157-163
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• 2006

Our research dealt with micro fabrication using micro forming process. The goal of the research was to establish the limit of forming process concerning the size of forming material and formed shape. Flat-rolled ultra thin metallic foils of pure copper(3.0 and $1.0{\mu}m$ in thickness)and stainless steel($2.5{\mu}m$ in thickness) were used for forming material. We obtained the various shapes of micro channels as using designed forming process. $12-14{\mu}m$ wide and $9{\mu}m$ deep channels were made on $3.0{\mu}m$ thick foil and $6{\mu}m$ wide and $3{\mu}m$deep channels were made on $1.0{\mu}m$ thick foil. Si wafer die for forming was fabricated by using etching technique. And the relation of etching time and die dimension was investigated for fabricating precisely die groove. For the forming, die and metal foil were vacuum packed and the forming was conducted with a cold isostatic press. The formed channels were examined in terms of their dimension, surface qualities and potential for defects. Base on the examinations, formability of ultra thin metallic foil was also discussed. Finally, we compared the forming result with simulation. The result of research showed that metal forming technology is promising to produce micro parts.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.1982-1988
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• 2002

Micro-injection molding and microfluidic devices with the help of MEMS technologies including the LIGA process are expected to play important roles in micro-system industries, in particular the bio-application industry, in the near future. Understanding fluid flows in micro-channels is important since micro-channels are typical geometry in various microfluidic devices and mold inserts for micro-injection molding. In the present study, Part 1, an experimental investigation has been carried out to understand the detailed flow phenomena in micro-channel filling process. Three sets of micro-channels of different thickness (40um,30um and 2011m) were fabricated using SU-8 on silicon wafer substrate. And a flow visualization system was developed to observe the filling flow into the micro-channels. Experimental flow observations are extensively made to find the effects of pressure, inertia force, viscous force and surface tension. A dimensional analysis for experimental results was carried out and several relationships A dimensionless parameters are obtained.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.2 s.43
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• pp.1-8
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• 2007

A flat fluorescent lamp (FFL) was developed as a light source for LCD TV Backlight. The channels of FFL were realized by forming the flat glass at high temperature. The performance of the backlight with FFL was shown to improve by optimizing the FFL channel profile that has elliptical shape, 4.4 mm height and 1.4 mm sealing distance. In this paper, the brightness uniformity of LCD TV backlights was investigated by optical simulation of FFL channel profiles. The brightness of LCD TV using FFL with the optimized channel profile was shown to be $576\;cd/m^2$.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.215-220
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• 2008

A microchannel PCHE is manufactured by the two technologies of micro photo-etching and diffusion bonding. In this paper, heat transfer and pressure drop characteristics by applying various configuration for the flow channel in the microchannel PCHE is experimentally investigated. The flow channel configurations are designed three types such as straight, wavy and offset strip channels. The performance experiment of each configuration is performed for Reynolds numbers in ranges of $100{\sim}700$ under various flow conditions for the hot side and the Reynolds number of cold side is fixed at 350. The inlet temperatures of the hot side and cold side are conducted as $40^{\circ}C$ and $20^{\circ}C$, respectively. The heat transfer performance of wavy channel, which was similar to that of offset strip channel, was much higher than that of straight channel. The effectiveness of wavy channel and offset strip channel was evaluated as about $0.5{\sim}0.9$. The pressure drop of wavy channel was highest among configurations and that of offset strip channel was lower than that of straight channel because the round curved surface of each strip edge was reduced the pressure loss.