Research Areas > Flow Control Based on Microfluidics & Nanofluidics

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In-situ quantitative visualization of water distribution in a fuel cell using X-ray imaging techniqu...

Post Image Due to energy crisis, renewable energies such as fuel cell technology are receiving large attention. In particular, PEFC (polymer electrolyte fuel cell) is well-suited for transport vehicles. For a PEFC, pertinent water management (supply and discharge) is essential to maintain the efficiency of the fuel cell. Therefore, water management problem is very important and should be solved for commercialization of this technology. In this study, a digital X-ray imaging technique is employed to measure the water distribution and movement of liquid phase inside the fuel cell. Using X-r...   내용 보기

Visualization of pico-liter droplet formation and air bubbles inside piezo inkjet head

Post Image The inkjet printing technology has a number of practical applications such as basic type-printing, fabrication of color filter of LCD panels or fabrication of fine electrical circuits. To improve the inkjet printing technology, it is essential to study the formation of fine droplets. However, it is not easy to visualize directly the dynamic behavior of inkjet droplets due to the inkjet head and high acceleration of the droplet (< 7×104g). In this study, advanced imaging technique including a high speed camera and a long distance microscope was used to observe the droplet for...   내용 보기

Swimming trajectory of copepod measured by DHPTV

Post Image Zooplankton plays an important role in aquatic life food chain as a food resource linking phytoplankton to fishes. Among such organisms, the copepod, found ubiquitously in water, is the most important one, representing 50-80% of all zooplankton. Copepods which belongs to the maxillopoda class are very important to global ecological equilibrium and the carbon cycle. The usual length of adults is 1-2mm, but some species can be as short as 0.2 mm and others may be as long as 10mm. The copepods’ ability to move vertically using marine current in an appropriate way is comparable to ...   내용 보기

DHPTV measurement of swimming trajectory of phytoplankton causing red-tide

Post Image DHPTV was employed to measure 3D free-swimming motion  of micro-organisms. Making chain formation, C. polykrikoides increase its swimming velocity and change its swimming mode to helical motion. The increasing swimming velocity is closely related with dense-blooming red-tides.   내용 보기

3D measurement of inertial migration of microspheres in a micro-scale pipe flow

Post Image  The inertial migration of neutrally buoyant spherical particles suspended in a micro-scale pipe flow was investigated in a Reynolds number range of 1.6 ≤ Re ≤ 77.4. A microtube, 350 μm in diameter, was used for the micro-scale pipe flow, and the ratios of the tube diameter (D) to the particle diameter (d) were D/d = 50, 23, and 12. The three-dimensional positions of the particles were measured using a digital holography technique, and the detailed structures of the Segré-Silberberg annulus were visualized. By analyzing the probability density distributions of the partic...   내용 보기

Axis-switching of non-axisymmetric microdroplet ejected from inkjet with an elliptical nozzle

Post Image Dynamic behaviors of the microdroplet ejected from the inkjet printhead with an elliptical nozzle are investigated using a high-speed micro-imaging system. The elliptic geometry of the nozzle induces elliptical cross section of the ejected droplet and the periodic switching of its major and minor axes. From the temporally-resolved measurement of droplet configuration based on the reproducibility of drop formation, the frequency responses and the viscous damping rates of the droplet oscillations are analyzed. The discrepancies in the dominant frequency and the decaying time consta...   내용 보기

Tomographic measurement of volume variation in gas diffusion layer under freeze and thaw cycles

Post Image  Synchrotron X-ray computed tomography was employed to measure the volume variation of gas diffusion layer (GDL) for polymer electrolyte fuel cell (PEFC). The study was conducted using 3D reconstruction (or a 3D rendering software) of orthoslice images. Especially, the temporal variation of structural parameters such as porosity was measured under freeze and thaw cycles. The freezing and thawing cycle were generated using a CRYO-system and an external light source alternatively. As a result, the structural parameters such varied significantly between the successive freeze/...   내용 보기

Lateral and cross-lateral focusing of spherical particles in a square microchannel

Post Image The inertial migration of particles in micro-scale flows has received much attention due to its promising applications, such as the membrane-free passive separation of particles or cells. The particles suspended in rectangular channels are known to be focused near the centers of each channel face as the channel Reynolds number (RC) increases due to the lift force balance and the hydrodynamic interactions of the particles with the wall. In this study, the three-dimensional positions of neutrally buoyant spherical particles inside a square microchannel are measured using the digi...   내용 보기

The impact and spreading dynamics of a graphene suspension droplet on a solid surface

Post Image Inkjet printing technology is a fast, non-contact, and low-cost methodology that precisely delivers various types of micro-scale liquid droplets onto a targeted substrate. This technology has recently been employed for the precise fabrication of three-dimensional (3-D) structures beyond conventional typography for advantages in spatial resolution and efficiency. The impact and spreading dynamics of a droplet is important physical phenomena which are used in inkjet printer. Here, we studied spreading dynamics of a graphene suspension droplet impacting on a solid surface using hi...   내용 보기