Ho-Young Kim is a mechanical engineer and an academic. He is a Professor and chair in the Department of Mechanical Engineering at Seoul National University. Kim's research interests encompass fluid mechanics, biofluid dynamics, microfluidics, soft matter, and their applications in bio-inspired soft mechanics, biomimetic soft robotics, nanofluidics, and renewable energy. Among numerous awards, he is the recipient of SNU President's Research Excellence Award, Gasan Award for Research Excellence and the Namheon Award for Research Excellence from the Korean Society of Mechanical Engineers. Kim is a Fellow of the American Physical Society. He has served as an Associate Editor for Droplet.
Education Kim obtained his B.S. in Mechanical Engineering from Seoul National University in 1994. In 1996, he pursued an S.M. (Master of Science) in Mechanical Engineering at the Massachusetts Institute of Technology (MIT) in Cambridge and earned his Ph.D. in Mechanical Engineering from MIT in 1999.
Career Kim began his career as a Senior Research Scientist as Military Service at the Korea Institute of Science and Technology from 1999 to 2004. During the military stint, he held positions as a Visiting Scholar at the Laboratory for Manufacturing and Productivity at the Massachusetts Institute of Technology (MIT) in 2001 and a Visiting Scientist at the University of Cambridge, in 2002. In 2004, he worked as a Postdoctoral Fellow in the Division of Engineering and Applied Sciences at Harvard University. He then joined Seoul University as an assistant professor in the same year and has held the position of Professor in the Department of Mechanical Engineering at the Seoul National University since 2014. Kim has held numerous professional appointments, including Track Chair for the World Congress on Biomechanics 2022 and co-chair for the International Conference on Nature Inspired Surface Engineering 2020, and organizer for the IUTAM Symposium on Capillarity and Elastocapillarity in Biology 2024.
Research Kim's research has focused on biofluid mechanics, capillarity, bubbles, nanofabrication, and soft matter, and has integrated experimental and theoretical approaches.
Biofluid mechanics Motivated by the ability of water striders to jump off water surface without sinking, Kim studied how super-water-repellent solids can be disengaged from water. He showed that a tiny superhydrophobic sphere can bounce off water surface when it impacts onto water with speeds of a narrow range. By studying the force and energy required to lift a solid object clear from the water surface, he found that a drastic degree of energy saving (up to 99%) is achieved when lifting a superhydrophobic object as compared with an object with moderate wettability. He also obtained the load supported by small floating objects as a function of the contact angle, and the sinking speeds of small but heavy solids into either inviscid or viscous liquids. These hydrodynamic studies eventually allowed him to capture the essential physics behind water jumping of water striders and to build a robotic water strider. He has extended his interests to the jumps of terrestrial insects, and solved the motion of a simple jumper (elastic hoop) to predict its maximum jump height accurately. In addition to the locomotion of semi-aquatic arthropods, he studied thrust generation of flapping appendages of swimming robots and animals. He found a kinematic condition of a compliant, beating fin for maximizing the thrust of a robotic fish. He also found that flapping paddles, tails, and fins of ducks, standing dolphins, and starting fish generate thrust by forming a vortical structure different from a conventional starting-stopping vortex paradigm, which allowed him to construct a scaling law to predict the thrust of the flapping plate in the absence of a free stream velocity. He also obtained a universal scaling law for the lift of hovering insects through simple scaling arguments of the strength of the leading edge vortex and the momentum induced by the vortical structure. In addition, his collaborative work used a fluttering flag to devise a novel scheme to generate electric power based on triboelectrification.
Capillarity Upon the basis of the pioneering theory of elastocapillarity, Kim continued to investigate the bending of thin elastic objects due to interfacial forces as they touch the liquid-fluid interface. He formulated the elastic deformation of elastic sheets under the line force of surface tension and the loading due to hydrostatic and Laplace pressures, and solved the free-boundary problem as the location of the meniscus is a part of the solution. The problems that he investigated include a two-dimensional paintbrush, a bubble-actuated paddle, and a floating flexible leg. He investigated the clustering behavior of micropillars and lamellae as a liquid film evaporates and pulls the solid structures together due to surface tension effects. He has also expanded this research to hygroscopic poroelastic structures, like paper, that deform with impregnation of water. The development of micro- and nanofabrication technology has enabled the formation of microscopically rough surfaces with tailored topography. Such surface textures magnify either wettability or water-repellency of smooth surfaces, which used to be impossible. He investigated the dynamics of liquid drops deposited on superhydrophilic textured surfaces to find that the spreading dynamics are qualitatively different from those on smooth surfaces and obtained the various scaling laws that govern the hemiwicking dynamics. Noting that writing with ink involves the similar process of superwetting of rough surfaces (paper) from a moving source (pen), he mathematically analyzed the process of writing. He also showed the effectiveness of superhydrophilic surfaces in collecting water from humid air via dewing, and modeled the shape of large drops on superhydrophobic surfaces. Using the micro- and nanofabrication technology, he also generated surfaces with super- wettability-contrast, such that superhydrophobic areas are surrounded by superhydrophilic area or vice versa. Liquid drops impacting on the micro-wetting patterned surfaces exhibit novel and even aesthetically pleasing dynamic behaviors, leading to the formation of various deposit morphologies such as radiating liquid spokes and liquid rings.
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