코팅 두께에 따른 친수성 무기 필름의 특성 분석

정연호,최원석,신용탁,이민지,김희곤,Joung, Yeunho,Choi, Won Seok,Shin, Yongtak,Lee, Minji,Kim, Heekon 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.6

In this paper, we present a novel hydrophilic coating material (Wellture Finetech, Korea) which can be utilized as a coating layer for anti-contamination for electrical and electronic system. The coating material was deposited on 4 inch silicon wafer with several different film thickness. The film thickness was controlled by spin coating speed. After curing of the film, we have scratched by permanent marker to check self-cleaning property of the film. Also we have executed several mechanical tests of the films. As the spin coating speed is increased, the film thickness was thinned from 230 nm to 125 nm. Contact angle of the film was lowered from $30^{\circ}$ to $12^{\circ}$ as the spin coating speed is increased from 700 to 2,500 rpm. On permanent marker scratched film surface coated at 1,000 rpm, we have poured regular city water to investigate self cleaning property of the film. The scratches were gradually separated from the film surface due to super-hydrophilicity of the film. Hardness of spin coated film was 9H measured by ASTM D3363 method. and adhesion of all film was 5B tested by ASTM D3359 method. Also, to get exact hardness value of the film, we have utilized a nano-indenter. As spin speed is increased, the hardness of film was increased from 3 GPa to 5 GPa.

기판 각도에 따른 탄소나노월의 성장 특성

김성윤,정연호,한재찬,최원석,Kim, Sung Yun,Joung, Yeun-Ho,Han, Jae Chan,Choi, Won Seok 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.9

The carbon nanowall (CNW) is a carbon-based nanomaterials and it was constructed with vertical structure graphenes and it has the highest surface density among carbon-based nanostructures. In this study, we have checked the growth properties of CNW according to the substrate angle. Microwave plasma enhanced chemical vapor deposition (PECVD) system was used to grow CNW on Si substrate with methane ($CH_4$) and hydrogen ($H_2$) gases. And, we have changed the substrate angle from $0^{\circ}$ to $90^{\circ}$ in steps of $30^{\circ}$. The planar and vertical conditions of the grown CNWs according to the substrate angle were characterized by a field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). In case of the growth angle increases, our experimental results showed that the length of the CNW was shortened and the content of carbon component was decreased.

무선 압력센서를 이용한 실시간 맥박수 측정기 개발

최상동,조성환,정연호,Choi, Sang-Dong,Cho, Sung-Hwan,Joung, Yeun-Ho 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.5

Among the various physiological information that could be obtained from human body, heartbeat rate is a commonly used vital sign in the clinical milieu. Photoplethysography (PPG) sensor is incorporated into many wearable healthcare devices because of its advantages such as simplicity of hardware structure and low-cost. However, healthcare device employing PPG sensor has been issued in susceptibility of light and motion artifact. In this paper, to develop the real-time heart rate measurement device that is less sensitive to the external noises, we have fabricated an ultra-small wireless LC resonant pressure sensor by MEMS process. After performance evaluation in linearity and repeatability of the MEMS pressure sensor, heartbeat waveform and rate on radial artery were obtained by using resonant frequency-pressure conversion method. The measured data using the proposed heartbeat rate measurement system was validated by comparing it with the data of an commercialized heart rate measurement device. Result of the proposed device was agreed well to that of the commercialized device. The obtained real time heartbeat wave and rate were displayed on personal mobile system by bluetooth communication.

실시간 맥박 및 혈압 측정을 위한 폴리머 기판 압력센서 개발

김진태,김성일,정연호,Kim, Jin-Tae,Kim, Sung Il,Joung, Yeun-Ho 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.9

In this study, we introduce a polymer(polyimide) based pressure sensor to measure real-time heart beat and blood pressure. The sensor have been designed with consideration of skin compatibility of material, cost effectiveness, manufacturability and wireless detection. The designed sensor was composed of inductor coils and an air-gap capacitor which generate self-resonant frequency when electrical source is applied on the system. The sensor was obtained with metalization, etching, photolithography, polymer adhesive bonding and laser cutting. The fabricated sensor was shaped in circular type with 10mm diameter and 0.45 mm thickness to fit radial artery. Resonant frequencies of the fabricated sensors were in the range of 91~96 MHz on 760 mmHg pressurized environment. Also the sensor has good linearity without any pressure-frequency hysteresis. Sensitivity of the sensor was 145.5 kHz/mmHg and accuracy was less than 2 mmHg. Real-time heart beat measurement was executed with a developed hand-held measurement system. Possibility of real-time blood pressure measurement was showed with simulated artery system. After installation of the sensor on skin above radial artery, simple real blood pressure measurement was performed with 64 mmHg blood pressure variation.

LC 공진형 압력 센서를 이용한 돼지 경골 동맥의 실시간 혈압 측정

최원석,김진태,정연호,Choi, Won-Seok,Kim, Jin-Tae,Joung, Yeun-Ho 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.6

We have developed an implantable wireless sensor for real time pressure monitoring of blood circulation system. MEMS (micro-electro-mechanical system) technology was adopted as a sensor development method. The sensor is composed of photolithographically patterned inductors and a distributed capacitor in gap between the inductors. A resulting LC resonant system produces its resonant frequency in range of 269 to 284 MHz at 740 mmHg. To read the resonant frequency changed by blood pressure variation, we developed a custom readout system based on a network analyzer functionality. The bench-top testing of the pressure sensors showed good mechanical and electrical functionality. A sensor was implanted into tibial artery of farm pig, and interrogated wirelessly with accurate readings of blood pressure. After 45 days, the sensor's electrical response and histopathology were studied with good frequency reading and biocompatibility.

인체 삽입용 LC 공진형 혈압 센서 디자인 및 제작

김진태,김성일,정연호,Kim, Jin-Tae,Kim, Sung Il,Joung, Yeun-Ho 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.3

In this paper, we present a MEMS (micro-electro-mechanical system) implantable blood pressure sensor which has designed and fabricated with consideration of size, design flexibility, and wireless detection. Mechanical and electrical characterizations of the sensor were obtained by mathematical analysis and computer aided simulation. The sensor is composed of two coils and a air gap capacitor formed by separation of the coils. Therefore, the sensor produces its resonant frequency which is changed by external pressure variation. This frequency movement is detected by inductive coupling between the sensor and an external antenna coil. Theoretically analyzed resonant frequency of the sensor under 760 mmHg was calculated to 269.556 MHz. Fused silica was selected as sensor material with consideration of chemical and electrical reaction of human body to the material. $2mm{\times}5mm{\times}0.5mm$ pressure sensors fitted to radial artery were fabricated on the substrates by consecutive microfabrication processes: sputtering, etching, photolithography, direct bonding and laser welding. Resonant frequencies of the fabricated sensors were in the range of 269~284 MHz under 760 mmHg pressure.

Quatrz 웨이퍼의 직접접합과 극초단 레이저 가공을 이용한 체내 이식형 혈압센서 개발

김성일,김응보,소상균,최지연,정연호,Kim, Sung-Il,Kim, Eung-Bo,So, Sang-kyun,Choi, Jiyeon,Joung, Yeun-Ho 대한의용생체공학회 2016 의공학회지 Vol.37 No.5

In this paper we present an implantable pressure sensor to measure real-time blood pressure by monitoring mechanical movement of artery. Sensor is composed of inductors (L) and capacitors (C) which are formed by microfabrication and direct bonding on two biocompatible substrates (quartz). When electrical potential is applied to the sensor, the inductors and capacitors generates a LC resonance circuit and produce characteristic resonant frequencies. Real-time variation of the resonant frequency is monitored by an external measurement system using inductive coupling. Structural and electrical simulation was performed by Computer Aided Engineering (CAE) programs, ANSYS and HFSS, to optimize geometry of sensor. Ultrafast laser (femto-second) cutting and MEMS process were executed as sensor fabrication methods with consideration of brittleness of the substrate and small radial artery size. After whole fabrication processes, we got sensors of $3mm{\times}15mm{\times}0.5mm$. Resonant frequency of the sensor was around 90 MHz at atmosphere (760 mmHg), and the sensor has good linearity without any hysteresis. Longterm (5 years) stability of the sensor was verified by thermal acceleration testing with Arrhenius model. Moreover, in-vitro cytotoxicity test was done to show biocompatiblity of the sensor and validation of real-time blood pressure measurement was verified with animal test by implant of the sensor. By integration with development of external interrogation system, the proposed sensor system will be a promising method to measure real-time blood pressure.

허리통증을 가진 엘리트 야구선수의 플라이오메트릭스 트레이닝이 어깨 근 기능에 미치는 영향

안나영(Ahn, Na-Young),정연호(Joung, Yeon-Ho),김기진(Kim, Ki-Jin) 한국코칭능력개발원 2015 코칭능력개발지 Vol.17 No.4

동잡음 저감을 위한 심전도 전극 특성에 대한 연구

강영환,박재순,조범기,최상동,정연호,Kang, Young-Hwan,Park, Jae-Soon,Cho, Bum-Ki,Choi, Sang-Dong,Joung, Yeun-Ho 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.6

In this paper, we introduce an electrocardiogram (ECG) system designed to solve problems caused by wetgels and motion artifacts in measuring active movement. The system is called a dry-contact ECG and was designed by considering impedance matching between skin and electrode as well as the frictional electricity between electrode and clothes. In order to create the system, we measured impedance on the skin-electrode interface, and the result was applied to the electronic circuit scheme. Moreover, we added an electrode on the back of the measurement electrode to make a flow path to ground the electrical noise. The final ECG circuit and novel electrode were used to detect real human cardiac signals from a subject who was tested while standing still and walking. The signals obtained from the two activities were nicely shaped, without any motion artifact noise. We took electrode size into account in this study because the impedance depended on the area of the electrode. An electrode of 50 mm diameter showed the best curve for the ECG signal without any electrical noise.

반응가스의 변화에 따른 탄소나노월의 성장 및 저항 특성

김성윤,이상준,최원석,정연호,임동건,Kim, Sung Yun,Lee, Sangjoon,Choi, Won Seok,Joung, Yeun-Ho,Lim, Dong-Gun 한국전기전자재료학회 2014 전기전자재료학회논문지 Vol.27 No.4

Graphite electrodes are used for secondary batteries, fuel cells, and super capacitors. Research is underway to increase the reaction area of graphite electrodes. In this study, we have investigated the growth properties of carbon nanowall (CNW) according to the ingredient of gas. Microwave plasma enhanced chemical vapor deposition (MPECVD) system was used to grow CNW on Si substrate with a variety of the reaction gas. The planar and vertical growth conditions of the grown CNWs according to the ingredient of the gas were characterized by a field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). The electrical characteristics of CNWs were analyzed using a 4-point probe.