• Journal of the Korean Society of Visualization
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• v.1 no.1
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• pp.75-81
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• 2003

A custom micro-PIV optics assembly has been used to measure the flow fold inside a T-junction of a microchannel. The micro-PIV system consists of microscope objectives of various magnifications, a dichroic cube, and an 8-bit CCD camera. Fluorescent particles of diameters 620 nm have been used with a Nd:YAG laser and color filters. A programmable syringe pump with Teflon tubings were used to inject particle-seeded distilled water into the channel at flow rates of 2.0, 4.0, 6.0 mL/hr. The micro-channels are fabricated with PDMS with a silicon mold, then O$_{2}$ -ion bonded onto a slide glass. Results show differences in flow characteristics and resolution according to fluid injection rates, and magnifications, respectively. The results include PIV data with vector-to-vector distances of 2 $\mu$m with 32 pixel-square interrogation windows at 50$\%$ overlap.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.6
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• pp.682-687
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• 2004

Y-junction microchannels are widely used as a flew mixer. Fluids are entered from two branch channels and merged together at a combined channel. In this study, we suggest a simple method to create the fluid digitization using flow instability phenomena. Two immiscible liquids (water/oil) are infused continuously to each Y-junction inlets. Because of the differences in fluid and flow properties at the interface, oil droplet is formed automatically followed by flow instability. In order to clarify the hydrodynamic aspects involved in oil droplet formation, a quantitative flow visualization study has performed. Highly resolved velocity vector fields are obtained by a micro-PIV technique, so that detail flow structures around the droplet are illustrated. In this study, fluorescent particles were mixed with water only for visualization of oil droplet and velocity field measurement in water flow.

• Journal of the Korean Society of Visualization
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• v.3 no.2
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• pp.45-50
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• 2005

Electro-osmotic flow (EOF) instability in a microchannel has been experimentally investigated using a micro-PIV system. The micro-PIV system consisting of a two-head Nd:Yag laser and cooled CCD camera was used to measure instantaneous velocity fields and vorticity contours of the EOF instability in a T-shape glass microchannel. The electrokinetic flow instability occurs in the presence of electric conductivity gradients. Charge accumulation at the interface of conductivity gradients leads to electric body forces, driving the coupled flow and electric field into an unstable dynamics. The threshold electric field above which the flow becomes unstable and rapid mixing occurs is about 1000V/cm. As the electric field increases, the flow pattern becomes unstable and vortical motion is enhanced. This kind of instability is a key factor limiting the robust performance of complex electrokinetic bio-analytical devices, but can also be used for rapid mixing and effective flow control fer micro-scale bio-chips.

• Journal of the Korean Society of Visualization
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• v.8 no.4
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• pp.31-37
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• 2010

In this study, a novel hybrid micro/nano PIV system combining defocusing and TIRFM technique has been developed for the multiscale flow measurement. With the developed system, both far and near field velocity fields have been measured simultaneously in a 2D straight microchannel and the particle trajectories were extracted by the nearest tracking algorithm. The shear rate values taken from experimental results have been estimated by comparing with the analytical solution of 2D Poiseuille flow and it is confirmed that the result shows good agreement with the theoretical value.

• 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.

• 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.

• Journal of the KSME
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• v.43 no.2
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• pp.32-37
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• 2003

• Journal of the Korean Society of Visualization
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• v.1 no.1
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• pp.16-21
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• 2003

• Journal of the Korean Society of Visualization
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• v.8 no.3
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• pp.29-34
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• 2010

This paper proposes a design method to provide uniform flow in a microreactor. Uniform momentum approach is adopted with 10 pillars before and after the chamber having a different slope inlet channel. The slope and number of pillars are two factors to make a uniform flow in the microreactor, covering the hexagonal gold layer. The CFD analysis about the designed microreactor is carried out and the velocity vector field measurements are made in the fabricated microreactor by micro PIV technique. The uniformity of microreactor flow was confirmed by both numerical simulation and experimental results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.1
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• pp.1-8
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• 2009

Recently microscale biofluid flows have been receiving large attention in various research areas. However, most conventional imaging techniques are unsatisfactory due to difficulties encountered in the visualization of microscale biological flows. Recent advances in optics and digital image processing techniques have made it possible to develop several advanced micro-PIV/PTV techniques. They can be used to get quantitative velocity field information of various biofluid flows from visualized images of tracer particles. In this paper, as new advanced micro-PIV techniques suitable for biofluid flow analysis, the basic principle and typical applications of the time-resolved micro-PIV and X-ray micro-PIV methods are explained. As a 3D velocity field measurement technique for measuring microscale flows, holographic micro-PTV method is introduced. These advanced PIV/PTV techniques can be used to reveal the basic physics of various microscale biological flows and will play an important role in visualizing veiled biofluid flow phenomena, for which conventional methods have many difficulties to analyze.