• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.922-929
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• 2006

In this study, flow characteristics of the FPN (Fountain Pen Nano-Lithography) using active membrane pumping are investigated. This FPN has integrated chamber, micro channel, and high capacity reservoir for continuous ink feed. The most important aspect in this probe provided control of fluid injection using active membrane pumping in chamber. The flow rates in channel by capillary force are theoretically analyzed, including the control of mass flow rates by deflection of membrane. The above results are compared with numerical simulations that calculated by commercial code, FLUENT. The velocity of fluid in micro channel shows linear behaviors. And the mass flows are proportional to the second order function of pumping pressure that is imposed to membrane.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.5 s.236
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• pp.707-715
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• 2005

In this work, Scalar Passive code in Lattice Boltzmann Method is employed to simulate two-phase flow of low Reynolds number in a micro-channel. The mixing characteristics in a micro-channel is a function of Peclet number. The mixing length increases with the Peclet number. It is found that with the inclusion of static elements at the channel, rapid mixing of two liquids can be achieved, as shown by the results of computer simulations. The enhancement in mixing performance is thought to be caused by the generation of eddies and by lateral velocity component when the mixture flows past static elements. The results indicate that the size of static element has more effect on the mixing than the number of static element.

• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.49-50
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• 2002

In micro-channels, the electro-viscous effect is caused by the electrical double layer on pressure-driven liquid flow. Velocity fields of flow inside micro-channels were measured using micro-PIV system for investigating the electro-viscous effect. De-ionized water and aqueous NaCl solutions with four different concentrations were used as working fluid in a PDMS micro-channel of $100{\mu}m$ width and $66{\mu}m$ height. The pressure gradient, dP/dx, was determined from the pre-determined input flow rate Q of syringe pump. The mean velocity $u_m$ used for calculating Reynolds number was obtained from the PIV velocity field data. These are used to plot the pressure gradient as a function of Reynolds numbers. The pressure gradient far lower concentration solution $(10^{-5}\;M)$ was higher than that for the higher concentration solution. The increase of flow resistance was about $30\%\;and\;37.5\%$ at Re=0.02 and 0.06, respectively.

• Journal of Fisheries and Marine Sciences Education
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• v.25 no.5
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• pp.1102-1109
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• 2013

An numerical analysis was performed to obtain the design parameters for parallel micro-channels. The parallel micro-channels consist of 10 square channels with a hydraulic diameter of 300 ${\mu}m$ and inlet/outlet manifolds. The channel length is 5mm, 10mm and 40mm respectively. Mass flux was set between 200~600kg/m2s as inlet boundary condition and atmospheric pressure was set as outlet boundary condition. The pressure drop in channels and manifolds were estimated by using the Shah and London correlation and the flow uniformity was represented by the velocity distributions with dimensionless velocity. The results show that the flow uniformity in channels depends on shapes of manifolds, length and mass flux.

• Journal of Biomedical Engineering Research
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• v.38 no.1
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• pp.1-8
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• 2017

The successful synthesis of hyaluronic acid micro-threads is very promising approach for the broad application in tissue engineering such as dermal fillers. Because hyaluronic acid has the excellent biocompatibility and ability to maintain the moisture of up to several hundred times its own weight. In order to generate the hyaluronic acid micro-threads in microfluidic system, we employed two-phase flow microfluidic chip to make a rapid synthesis of the hyaluronic acid hydrogel. Hyaluronic acid was mixed with 0.02N NaOH solution and 1, 4-Butanediol diglycidyl ether (BDDE) solution and then injected into core channel. The ethanol was used for the 3-dimensional micro-thread formation in sheath channel. We manipulated the diameter of HA micro-threads using controlling of flow rates in microfluidic chip, and showed the feasibility of immobilization in HA micro-threads with florescent substances. Also, the generated HA micro-threads were evaluated and showed the suitable properties with tensile strength, bending property, and swelling profiles for dermal fillers. As a result, we suggested an innovative method for microfluidic chip-based HA micro-threads which could safely be applied as dermal filler in tissue engineering.

• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.45-48
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• 2002

To investigate the flow related to the mixing, micro PIV measurements were performed in the middle plane of the channel. A passive micro mixer analyzed in this work has been designed in the shape of a three-dimensional microchannel and fabricated with PDMS molding process by KAIST. The mixing performance was evaluated for different flow rates using phenolphthalein and sodium hydroxide solutions. Results show that mixing is enhanced by the increase of flow rate, which yields stronger secondary flows with helical streamlines.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.5
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• pp.640-651
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• 2000

For the heat and fluid flow analyses of a parallel flow heat exchanger, an improved model considering the effect of flat tube with micro-channels is proposed. The effect of flow distribution on the thermal performance of a heat exchanger is numerically investigated. The flow distribution is examined by varying geometrical parameters, i.e., the position of the separators and the inlet/outlet, and the aspect ratio of micro-channels of the heat exchanger. The flow nonuniformities along the paths of the heat exchanger are proposed and observed to evaluate the thermal performance of the heat exchanger. The optimization using ALM method has been accomplished by minimizing the flow nonuniformity. It is found that the heat transfer rate of the optimized model is increased by 6.0% of that of the reference heat exchanger model, and the pressure drop by 0.4%

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.4
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• pp.349-354
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• 2010

Fuel cells have attracted enormous interest as new power sources because the cells can be used to solve the problem of environmental pollution as well as the natural-resource exhaustion problem. In this study, hydrogen-gas flow in microchannels of different shapes was numerically analyzed to improve the efficiency of a microfuel cell. Flow characteristics in six microchannels of different shapes but under identical boundary conditions were simulated. The analysis result shows that the flow characteristics such as velocity, uniformity, and flow rate, greatly depend upon the channel shape. This implies that the efficiency of microfuel cell can be expected to be increased by adopting the optimal configuration of channel shape for hydrogen-gas flow. The experimental results show that power density of a PEMFC with a microflow channel is higher than that of a PEMFC without a microflow channel; however, a durable catalyst is required in MEA.

• 한국가시화정보학회:학술대회논문집
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• 2007.11a
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• pp.84-87
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• 2007

Recently, many studies concern on the slip flow and slip length, which allow liquid flow to reduce drag force in microchannel. However, until now not enough investigation is performed experimentally to understand the slip flow in the superhydrophobic microchannel exhibiting riblet structures on vertical wall. Here we investigated and compared the slip flows according to the surface characteristics; hydrophilic, hydrophobic, and superhydrophobic wettabilities. Using the micro-PIV, velocity profiles can be obtained in the glass (hydrophilic), PDMS (hydrophobic), and micro-structured PDMS (superhydrophobic) microchannels. For both PDMS and superhydrophobic PDMS microchannels, we observed the slip effects showing the microscale slip lengths. Due to the micro-riblet, there are two distinctive flow characteristics on the riblet surface and the liquid meniscus in the valleys.

• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.51-52
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• 2002

Electro-osmotic flow in a PDMS microchannel of $66{\mu}m\;\times\;200{\mu}m\;\times\;3cm$ has been investigated using a micro PIV system. The field of view was $1056{\mu}m\;\times\;200{\mu}m$ and instantaneous velocity fields were obtained using two-frame cross-correlation method with $64\;\times\;64\;pixels^2$ interrogation window. In this study, we focused on the effect of applied electric field on the variation of internal flow with varying the electric field and seeding particles. The electro-osmotic flow shows a flat velocity profile and the mean velocity is proportional to the applied electric field.