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3차원 마이크로 파이버 플랫폼 구현을 통한 심장세포 수축력 변이 모델링
구상모(Sangmo Koo),Zhen Ma,Nathaniel Huebsch,Mohammad A. Mandegar,Brian Siemons,Steven Boggess,Bruce R. Conklin,Costas P. Grigoropoulos,Kevin E. Healy 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
The integration of 3D artificial fibrous platform by advanced laser-based direct writing (two-photon polymerization), and human induced pluripotent stem cells (hiPSCs) allows us to measure the physiolocal phenotypes and recapitulation of diverse cardiac diseases. And additional genome editing technologies also make it possible to mimic the realistic disease pathologies. Based on those techniques, it was possible to create the patient-customized 3D platform by fabricating the 3D microscale fibrous structure which has similar mechanical properties such as stiffness for cardiac disease research. 3D cardiac tissues are anchored between two flexible cantilevers, contraction (and relaxation) force was measured by measuring fiber deflection. It is served as force sensor, and showed the tissue mechanical resistance to contraction can regulated by external microenvironments.
전반사형광현미경법과 타원체맞춤 방법을 이용한 고체벽면 근처에서의 3 차원 박테리아 경로 추적
구상모(Sangmo Koo),진송완(Songwan Jin),이용구(Yongkoo Lee),전호정(Hojeong Jeon),유정열(Jung Yul Yoo) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
The motion of flagellated bacteria close to surfaces is relevant to understanding the early stage of Biofilm formation. When Bacterium cells are close to a surface, the cells often swim parallel to the surface in a circle for some time. The simplest and most effective way of understanding this motion is the individual cell tracking. In the present study, TIRFM is used to generate the evanescent wave near the surface so that it emits a green light due to eGFP gene transfection and illuminates a small specimen volume of about 100-㎚ depth. Also, using the PTV method, we can obtain the 3D motion data of bacteria near the surface. However, most of current 3D tracking methods, which are designed for spherical particles, is not optimized to track a bacteriumlike cell which is of a prolate ellipsoid. In this study, using the PTV method and proposing the ellipsoidal fitting to model the shape of bacteria realistically, we obtain the more accurate data of bacteria motion near the wall.
펨토초 레이저 가공을 이용한 3차원 약물 검사 시스템 구현
구상모(Sangmo Koo),Zhen Ma,Nathaniel Huebsch,Bruce R. Conklin,Costas P. Grigoropoulos,Kevin E. Healy 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
A human in vitro cardiac tissue model would help to understand the cardiovascular disease and develop new strategies for cardiac diseases such as arrhythmias. In this research, we developed in vitro a three-dimensional (3D) human artificial heart tissue by populating synthetic filamentous matrices using multi-photon absorption by the femtosecond laser. With this advanced fabrication method. two-photon polymerization, the bio-inspired cardiac tissue scaffold had fabricated with a cohort of 3D filamentous matrices that precisely regulated the structural alignment of cardiac tissue. By varying the mechanical properties such as thickness and stiffness of filamentous structure, different level of cardiomyocytes contractility abnormality and susceptibility to drug-induced cardiotoxicity were measured under different physical environments.
DPSS Laser에 의한 AsGeSeS,Ag/AsGeSeS 와 AsGeSeS/Ag/AsGeSeS 박막의 홀로그래픽 데이터
구용운(Yong-Woon Koo),구상모(Sang-Mo Koo),조원주(Won-Ju Cho),정홍배(Hong-Bay Chung) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.10
We investigated the diffraction grating efficiency by the DPSS laser beam wavelength to improve the diffraction efficiency on AsGeSeS & Ag/AsGeSeS thin film. Diffraction efficiency was obtained from DPSS(532㎚)(P:P)polarized laser beam on AsGeSeS, Ag/AsGeSeS and AsGeSeS/Ag/AsGeSeS thin films. As a result, for the laser beam intensity, 0.24 ㎽, single AsGeSeS thin film shows the highest value of 0.161% diffraction efficiency at 300 s and for 2.4 ㎽, it was recorded with the fastest speed of 50 s, which the diffraction grating forming speed is faster than that of 0.24 ㎽ beam. Ag/AsGeSeS and AsGeSeS/Ag/AsGeSeS multi-layered thin film also show the faster grating forming speed at 2.4 ㎽ and higher value of diffraction efficiency at 0.24 ㎽.
후열 처리에 따른 Ga<sub>2</sub>O<sub>3</sub>/4H-SiC 이종접합 다이오드 특성 분석
이영재,구상모,Lee, Young-Jae,Koo, Sang-Mo 한국전기전자재료학회 2020 전기전자재료학회논문지 Vol.33 No.2
Ga<sub>2</sub>O<sub>3</sub>/n-type 4H-SiC heterojunction diodes were fabricated by RF magnetron sputtering. The optical properties of Ga<sub>2</sub>O<sub>3</sub> and electrical properties of diodes were investigated. I-V characteristics were compared with simulation data from the Atlas software. The band gap of Ga<sub>2</sub>O<sub>3</sub> was changed from 5.01 eV to 4.88 eV through oxygen annealing. The doping concentration of Ga<sub>2</sub>O<sub>3</sub> was extracted from C-V characteristics. The annealed oxygen exhibited twice higher doping concentration. The annealed diodes showed improved turn-on voltage (0.99 V) and lower leakage current (3 pA). Furthermore, the oxygen-annealed diodes exhibited a temperature cross-point when temperature increased, and its ideality factor was lower than that of as-grown diodes.
김성수,구상모,Kim, Sung-Su,Koo, Sang-Mo 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.11
Silicon Carbide (SiC) is the material with the wide band-gap (3.26 eV), high critical electric field (~2.3 MV/cm), and high bulk electron mobility (~900 $cm^2/Vs$). These electronic properties allow attractive features, such as high breakdown voltage, high-speed switching capability, and high temperature operation compared to Si devices. In general, device design has a significant effect on the switching and electrical characteristics. It is known that in this paper, we demonstrated that the switching performance and breakdown voltage of IGBT is dependent with doping concentration of p-base region and drift layer by using 2-D simulations. As a result, electrical characteristics of SiC-IGBT deivce is higher breakdown voltage ($V_B$= 1,600 V), lower on-resistance ($R_{on}$= 0.43 $m{\Omega}{\cdot}cm^2$) than Si-IGBT. Also, we determined that processing time and cost is reduced by the depth of n-drift region of IGBT was reduced.
중성자 조사된 SiC Schottky Diode의 온도 의존 특성
김성수,구상모,Kim, Sung-Su,Koo, Sang-Mo 한국전기전자재료학회 2014 전기전자재료학회논문지 Vol.27 No.10
The temperature dependent characteristics on the properties of SiC Schottky Diode has been investigated. In this study, the temperature dependent current-voltage characteristics of the SiC Schottky diode were measured in the range of 300 ~ 500 K. Divided into pre- and post- irradiated device was measured. The barrier height after irradiation device at 500 K increased 0.15 eV compared to 300 K, the barrier height of pre- neutron irradiated Schottky diode increased 0.07 eV. The effective barrier height after irradiation increased from 0.89 eV to 1.05 eV. And ideality factor of neutron irradiated Schottky diode at 500 K decreased 0.428 compared to 300 K, the ideality factor of pre- neutron irradiated Schottky diode decreased 0.354. Also, a slight positive shift in threshold voltage from 0.53 to 0.68 V. we analyzed the effective barrier height and ideality factor of SiC Schottky diode as function of temperature.
이재상,구상모,이상렬,Lee, Jae-Sang,Koo, Sang-Mo,Lee, Sang-Yeol 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.9
The TFTs have been fabricated with 3 different geometry SID electrodes which have the same channel W/L ratio (W/L = 5) due to constant channel resistance, The 3 samples have different channel widths (350, 150, and 25 ${\mu}m$) and channel lengths (70, 30, and 5 ${\mu}m$) by fixed channel W/L ratio simultaneously on one chip for reliable comparisons. Resultant on-current and field effect mobility are proportional to the channel width, while the subthreshold swing is inversely proportional to the channel width mainly due to the change of contact resistance. These results show that the contact resistance strongly affects the device performances and should be considered in the applications.
용액 공정으로 형성된 n-ZTO/p-SiC 이종접합 열처리 효과
정영석,구상모,Jeong, Young-Seok,Koo, Sang-Mo 한국전기전자재료학회 2015 전기전자재료학회논문지 Vol.28 No.8
We investigated the effects of annealing on the electrical and thermal properties of ZTO/4H-SiC heterojunction diodes. A ZTO thin film layer was grown on p-type 4H-SiC substrate by using solution process. The ZTO/SiC heterojunction structures annealed at $500^{\circ}C$ show that $I_{on}/I_{off}$ increases from ${\sim}5.13{\times}10^7$ to ${\sim}1.11{\times}10^9$ owing to the increased electron concentration of ZTO layer as confirmed by capacitance-voltage characteristics. In addition, the electrical characterization of ZTO/SiC heterojunction has been carried out in the temperature range of 300~500 K. When the measurement temperature increased from 300 K to 500 K, the reverse current variation of annealed device is higher than as-grown device, which is related to barrier height in the ZTO/SiC interface. It is shown that annealing process is possible to control the electrical characteristics of ZTO/SiC heterojunction diode.