• Journal of the Korean Society of Visualization
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• v.13 no.1
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• pp.30-34
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• 2015

This study concerns flow and heat transfer characteristics of FC-72 condensing flow in a micro-channel. A computational model of condensing flow with a hydraulic diameter of 1 mm is constructed using the FLUENT computational fluid dynamics code. The computed void fraction contour plots are presented for different mass velocities. The smooth-annular, wavy-annular, transition and slug flows are observed with the model, which are quite similar to those observed in a micro-channel experiment. The computed two-phase condensing heat transfer coefficient is compared with previous empirical correlation for two-phase condensation heat transfer in micro-channels.

• 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.

• Laser Solutions
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• v.18 no.2
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• pp.11-13
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• 2015

Pressure-drop in a micro-channel is critical when a hole diameter is less then 100um with the high aspect ratio, more than 40. To minimize these pressure loss for micro-channel applications is important and there would be the best hole diameter, taper angle, and their combinations. In this work, the parametric study for laser drilling of anodized material is conducted to obtain the micro-channel hole with high aspect ratio.

• Design & Manufacturing
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• v.2 no.1
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• pp.45-50
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• 2008

Micro channel is to fabricate desired pattern on the polymer substrate by pressing the patterned mold against the substrate which is heated above the glass transition temperature, and it is a high throughput fabrication method for bio chip, optical microstructure, etc. due to the simultaneous large area patterning. However, the bad pattern fidelity in large area patterning is one of the obstacles to applying the hot embossing technology for mass production. In the present study, stamper of cross channel with width $100{\mu}m$ and height $50{\mu}m$ was manufactured using UV-LiGA process. Micro channel was manufactured using stamper manufactured in this study. Also replicability appliance was evaluated for micro channel and factors affected replicability were investigated using Taguchi method.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1777-1782
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• 2003

This paper presents the design, fabrication, and testing of the capillary-induced pressure drop valve, thermocapillary pumping of liquid droplet in hydrophilic channels and the splitting of droplet. The capillaryinduced pressure drop is derived with thermodynamic approach considering three-dimensional meniscus shape which is essential for calculating pressure drop in the diverging shape channel when the aspect ratio is close to one. The micro channel is fabricated via MEMS processes, which consists of the liquid stop valve to retard the liquid droplet, thermocapillary pumping region and the bifurcation region. Also the micro heaters are fabricated to drive the droplet by thermocapillary. The theoretical approaches agree well with the experimental data. The functionality of capillary valve is confirmed to be valid when the aspect ratio is smaller than one. To overcome the difficulty in splitting of the droplet due to the pressure drop in the general Y-shape channel, the protrusion shape is employed for easy splitting in the bifurcation channel.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.6
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• pp.421-425
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• 2016

Micro-EDM is one of the recent fine-machining technologies. Micro-EDM is widely used in precision processes because products manufactured via EDM are free from workpiece hardness. However, the debris produced during the process cause many problems such as reduced precision of the process. The first solution of this problem involves using the milling hole process. Micro-EDM hole process involves an electrode moving rapidly in the vertical direction via a servo system to disperse debris. However, this process can cause reduced work efficiency owing to contact between the electrode and workpiece. In this study, ultrasonic vibration is added to micro-EDM channel machining. Ultrasonic vibration removes the debris during machining and enables precision machining. Consequently, a clean work environment for the subsequent processes is maintained.

• 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.

• 한국가시화정보학회:학술대회논문집
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• 2004.12a
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• pp.125-134
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• 2004

The improvement of artificial respiration method has brought about the decrease in mortality of pulmonary diseases patients. Various respiratory curative methods, inclusive of HFOV (High Frequency Oscillatory Ventilation), have been developed for more effectual and less harmful management of acute respiratory failure. However, the mechanism of gas transfer and diffusion in a bronchiole has not yet been clarified in detail. As a first approach to the problem, we measured oscillatory flows in a Y-shaped micro-channels as bronchiole model by micro Particle Image Velocimetry(micro PIV). In order to establish the fundamental technique of PIV measurements on oscillatory air flow in a micro-channel, we used about 500-nm-diameter incense smoke particles, a diode laser, a high speed camera including an objective lens, and a HFOV, which is effective technique for medical care of pulmonary disease patients, especially, infants. The bronchiole model size is that parent tube is $500\{mu}m$ width and $500\{mu}m$ depth, and daughter tubes are $450\{mu}m$ width and $500\{mu}m$ depth. From this study made on the phenomenon of fluid in micro size bronchus branch of a lung, we succeeded to get time series velocity distribution in a micro scale bronchial mode. The experimental results of velocity distribution changing with time obtained by micro PIV can give fundamental knowledge on oscillatory airflow in micro-channel.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.5
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• pp.657-665
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• 2003

Several interesting results were obtained from the flow visualization experiment in the accompanying paper, Part I. in the present study, Part II, a numerical study has been carried out to explain the detailed flow phenomena in micro-channel filling process. Hele-Shaw flow approximation was applied to the micro-channel geometry based on the small characteristic length. And surface tension effect has been introduced on the flow front as the boundary condition with the help of a dynamic contact angle concept between the melt front and the wall. A dimensional analysis for numerical results was carried out and a strong relationship between dimensionless pressure and Capillary number is obtained. The numerical analysis results are compared with the flow visualization experimental observations. And the numerical system developed in the present study seems to be able to predict the interesting micro-channel filling flow characteristics observed from experiments.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1924-1926
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• 2001

A novel wet release process ($\mu$ CARP - Micro Channel Assisted Release Process) for releasing an extreme large-area plate structure without etching hole is proposed and experimented. Etching holes in conventional process reduce a effective area and degrade an optical characteristics by a diffraction. In addition, as the area of a released structure increases, the stietion becomes more serious. The proposed process resolves these problems by the introduction of a micro fluidic channel beneath the structure which will be released. In this paper, a 5 mm${\times}$5mm-single crystal silicon plate structure was released by the proposed $\mu$CARP without etch holes on the structure. The variation in etching time with respect to the of the introduced micro channel is also examined. This process is expected to be beneficial for the actuator of a nano-scale data storage and the scanning mirror.