Jihoon Kim

Bio: Jihoon Kim is an academic researcher from Sungkyunkwan University. The author has contributed to research in topics: Medicine & Microchannel. The author has an hindex of 10, co-authored 51 publications receiving 458 citations. Previous affiliations of Jihoon Kim include Konkuk University & Korean Ocean Research and Development Institute.

Direct measurement of slip flows in superhydrophobic microchannels with transverse grooves

Abstract: Slippage effects in microchannels that depend on the surface characteristics are investigated, taking into account hydrophilic, hydrophobic, and superhydrophobic wettabilities. Microscale grooves are fabricated along the vertical walls to form superhydrophobic surfaces, which enable both the visualization of the flow field near the walls and the direct measurement of the slip length. Velocity profiles are measured using microparticle image velocimetry and those in hydrophilic glass, hydrophobic polydimethylsiloxane (PDMS), and superhydrophobic PDMS microchannels are compared. For the hydrophilic glass surface, the velocity near the wall smoothly decreases to zero, which is consistent with the well-known, no-slip boundary condition. On the other hand, for the flow in the hydrophobic PDMS microchannel, the velocity profile approaches some finite value at the wall, showing a slip length of approximately 2μm. In addition, to directly measure the velocity in the superhydrophobic microchannel, transverse groove...

Direct alignment and patterning of silver nanowires by electrohydrodynamic jet printing.

Abstract: Highly aligned and patterned silver nanowires (Ag NWs) are investigated by using electrohydrodynamic (EHD) jet printing. Interaction between the flow field and the electric field as well as the mechanical stretching of the fiber jet can successfully align the Ag NWs inside the jet fiber. This technique can be applied in fabricating 1D nanostructures-based printed micro/nanoscale devices.

Flow structures around a flapping wing considering ground effect

Abstract: Over the past several decades, there has been great interest in understanding the aerodynamics of flapping flight, namely the two flight modes of hovering and forward flight. However, there has been little focus on the aerodynamic characteristics during takeoff of insects. In a previous study we found that the Rhinoceros Beetle (Trypoxylusdichotomus) takes off without jumping, which is uncommon for other insects. In this study we built a scaled-up electromechanical model of a flapping wing and investigated fluid flow around the beetle’s wing model. In particular, the present dynamically scaled mechanical model has the wing kinematics pattern achieved from the real beetle’s wing kinematics during takeoff. In addition, we could systematically change the three-dimensional inclined motion of the flapping model through each stroke. We used digital particle image velocimetry with high spatial resolution, and were able to qualitatively and quantitatively study the flow field around the wing at a Reynolds number of approximately 10,000. The present results provide insight into the aerodynamics and the evolution of vortical structures, as well as the ground effect experienced by a beetle’s wing during takeoff. The main unsteady mechanisms of beetles have been identified and intensively analyzed as the stability of the leading edge vortex (LEV) during strokes, the delayed stall during upstroke, the rotational circulation in pronation periods, and wake capture in supination periods. Due to the ground effect, the LEV was enhanced during half downstroke, and the lift force could thus be increased to lift the beetle during takeoff. This is useful for researchers in developing a micro air vehicle that has a beetle-like flapping wing motion.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Applications of Bio‐Inspired Special Wettable Surfaces

Abstract: In this review we focus on recent developments in applications of bio-inspired special wettable surfaces. We highlight surface materials that in recent years have shown to be the most promising in their respective fields for use in future applications. The selected topics are divided into three groups, applications of superhydrophobic surfaces, surfaces of patterned wettability and integrated multifunctional surfaces and devices. We will present how the bio-inspired wettability has been integrated into traditional materials or devices to improve their performances and to extend their practical applications by developing new functionalities.

Bioinspired self-cleaning surfaces with superhydrophobicity, superoleophobicity, and superhydrophilicity

Abstract: Self-cleaning methods currently employed are based on understanding of the functions, structures, and principles of various objects found in living nature. Three types of surfaces, including superhydrophobic, superoleophobic, and superhydrophilic, offer solutions to keep a surface clean. In this review article, an overview of self-cleaning surfaces inspired by nine biological objects is provided: lotus leaves, rice leaves, cicada wings, butterfly wings, snail shell, fish scale, shark skin, pitcher plant, and photosynthesis. These surfaces exhibit special properties such as low adhesion, low drag, anisotropic wetting, anti-reflection, directional adhesion, anti-fouling, photocatalysis, self-sterilizing, and anti-fogging. We discuss the differences between the superhydrophobic and superhydrophilic surfaces and perspectives for self-cleaning surfaces in the future.

Ag Nanowire Reinforced Highly Stretchable Conductive Fibers for Wearable Electronics

Abstract: Stretchable conductive fi bers have received signifi cant attention due to their possibility of being utilized in wearable and foldable electronics. Here, highly stretchable conductive fi ber composed of silver nanowires (AgNWs) and silver nanoparticles (AgNPs) embedded in a styrene‐butadiene‐styrene (SBS) elastomeric matrix is fabricated. An AgNW-embedded SBS fi ber is fabricated by a simple wet spinning method. Then, the AgNPs are formed on both the surface and inner region of the AgNW-embedded fi ber via repeated cycles of silver precursor absorption and reduction processes. The AgNW-embedded conductive fi ber exhibits superior initial electrical conductivity ( σ 0 = 2450 S cm −1 ) and elongation at break (900% strain) due to the high weight percentage of the conductive fi llers and the use of a highly stretchable SBS elastomer matrix. During the stretching, the embedded AgNWs act as conducting bridges between AgNPs, resulting in the preservation of electrical conductivity under high strain (the rate of conductivity degradation, σ / σ 0 = 4.4% at 100% strain). The AgNW-embedded conductive fi bers show the strain-sensing behavior with a broad range of applied tensile strain. The AgNW reinforced highly stretchable conductive fi bers can be embedded into a smart glove for detecting sign language by integrating fi ve composite fi bers in the glove, which can successfully perceive human motions.