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Younghak Cho,Beomjoon Kim,Seokkwan Hong,Jeongjin Kang 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.3
This paper deals with a novel structure for single-cell characterization which makes use of bimorph micro thermal actuators combined with electrical sensor device and integrated microfluidic channel. The goal for this device is to capture and characterize individual biocell. Quantitative and qualitative characteristics of bimorph thermal actuator were analyzed with finite element analysis methods. Furthermore, optimization for the dimension of cantilevers and integrated parallel systems with microfluidic channels is able to be realized through the virtual simulation for actuation and the practical fabrication of prototype of probes. The experimental value of probe deflection was in accordance with the simulated one.
Fabrication Methods for Microscale 3D Structures on Silicon Carbide
Younghak Cho,Jihong Hwang,Min-Soo Park,Bo Hyun Kim 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.23 No.12
Silicon carbide (SiC) is an attractive material for many industrial applications, such as semiconductors, electronic power devices, and optical and mechanical devices, owing to its wide bandgap, high thermal and wear resistance, and chemical inertness. Although SiC has superior properties, fabricating micro-features on SiC is very expensive and time-consuming. Many studies have introduced various fabrication methods utilizing physical, chemical, and thermal principles to remove SiC material. This paper reviews the state-of-the-art processes applicable for fabricating micro-3D structures on SiC, including etching, mechanical, thermal, and additive processes. The advantages and limitations of these processes are also discussed to guide the selection of processes suitable for SiC.
Distinct Mechanosensing of Human Neural Stem Cells on Extremely Limited Anisotropic Cellular Contact
Baek, Jieung,Cho, Soo-Yeon,Kang, Hohyung,Ahn, Hyunah,Jung, Woo-Bin,Cho, Younghak,Lee, Eunjung,Cho, Seung-Woo,Jung, Hee-Tae,Im, Sung Gap American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.40
<P>Human neural stem cells (hNSCs) can alter their fate choice in response to the biophysical cues provided during development. In particular, it has been reported that the differentiation of neural stem cells (NSCs) is enhanced by anisotropic contact, which facilitates focal adhesion (FA) formation and cytoskeletal organization. However, a biomolecular mechanism governing how the cells process the biophysical cues from these anisotropic geometries to their fate commitment is still poorly understood due to the limited availability of geometrical diversities (contact width above 50 nm) applicable to cell studies. Here, we firstly demonstrate that the biomolecular mechanism for enhanced neurogenesis on an anisotropic nanostructure is critically dependent on the resolution of a contact feature. We observed a totally different cellular response to anisotropic geometries by first utilizing a high-resolution nanogroove (HRN) structure with an extremely narrow contact width (15 nm). The width scale is sufficiently low to suppress the integrin clustering and enable us to elucidate how the contact area influences the neurogenesis of hNSCs at an aligned state. Both the HRN and control nanogroove (CN) pattern with a contact width of 1 μm induced the spontaneous topographic alignment of hNSCs. However, intriguingly, the focal adhesion (FA) formation and cytoskeletal reorganization were substantially limited on the HRN, although the cells on the CN showed enhanced FA formation compared with flat surfaces. In particular, the hNSCs on the HRN surface exhibited a strikingly lower fraction of nuclear yes-associated protein (YAP) than on the CN surface, which was turned out to be regulated by Rho GTPase in the same way as the cells sense the mechanical properties of the environment. Considering the previously reported role of YAP on neurogenesis, our finding newly substantiates that YAP and Rho GTPase also can be transducers of hNSCs to process topographical alternation to fate decision. Furthermore, this study with the unprecedented high-resolution nanostructure suggests a novel geometry sensing model where the functional crosstalk between YAP signaling and Rho GTPase integrally regulate the fate commitment of the hNSCs.</P> [FIG OMISSION]</BR>