• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.10
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• pp.741-744
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• 2013

In this study, we fabricated anodic aluminum oxide (AAO) membrane by two step anodizing process for pH detection. The structural properties were observed by X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). Electrochemical measurements of the pH sensor have been performed in capacitance-voltage (C-V) and drift rates. The characterization of AAO membrane exhibited high sensitivity (99.1 mV/pH) at second anodizing time of 4 min.

• Proceedings of the Korea Contents Association Conference
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• 2015.05a
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• pp.229-230
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• 2015

신생혈관 형성은 기존에 존재하는 혈관으로부터 새로운 혈관을 형성하는 기작으로 정상 세포에서 상처 치유, 세포의 발생 및 성장에 관여한다고 알려져 있다. 더 중요한 것은 이 기작이 암의 성장 및 전이에서도 매우 중요한 역할을 하고 있다는 사실이다. 특히, 엔지오제닌(Angiogenin)이 신생혈관형성을 촉진하는 것으로 알려져있다. 이러한 주요 물질을 최신 바이오칩 기술 중 하나인 액적 기반 미세유체 시스템을 활용하여 1 나노리터 수준의 시료 내에 존재하는 엔지오제닌을 정량하는 기술을 개발함으로써 현재 일반적으로 사용되고 있는 정량 기술에 비해 시간뿐만 아니라 비용을 절감할 수 있음을 보여주었다. 이외에도 본 연구에서 개발한 액적 기반 미세유체 시스템 기술은 수은과 같은 중금속의 검출도 가능하기 때문에 환경 센서로의 활용 가능성을 보여준다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.3
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• pp.294-298
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• 2004

Carbon nanotubes(CNTs) were synthesized by thermal chemical vapor deposition(CVD) method. To fabricate CNT gas sensor, catalyst metal layer was deposited on microstructure. The CNT gas detecting layer was grown by thermal CVD method on the catalyst metal layer. In order to investigate the gas sensing characteristics of the fabricated CNT gas sensor, it was exposed in NO$_2$ gas and sensitivity, response, and recovery time were measured. As the result, this sensor has better reproductibility and faster recovery time than another CNT gas sensors.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2537-2539
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• 2005

In many cases the systems are so complex that it is not possible to obtain reasonable models using physical laws. Also a model based on physical laws contains a number of unknown parameters even if the structure is derived from physical laws. These problems can be solved by system identification. In this paper, a nano stage system is selected as an example for system identification. The transfer functions of this system is derived by using state-space model structure based on input/output data through experiment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.404-405
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• 2008

In this work, we investigated the effect of the functionalized SWNT-polymer composites for increasing sensitivity and imparting selectivity to nanotube sensors. To do this, CNT -based gas sensors were fabricated with two types of dispersed SWNT solution involving different polymer resin of TEOS (Tetraethyl orthosilicate) or MTMS (Methyl trimethoxysilane) which is blended to adhere to substrate well. As the surfaces of TEOS and MTMS surrounding SWNTs remain functionalized to -OH and $-CH_3$ groups respectively after hardening, gas adsorption will be affected differently according to the type of gases. In the experiment, we examined the response of electrical conductance for alcohol vapour gas. As the result, the conductance in the sensors using TEOS decreased considerably while that of MTMS was nearly invariable.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.5
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• pp.510-517
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• 2004

A fine hot-wire is used both as a heating element and a temperature sensor in transient hot-wire method. The traditional sensor system is unnecessarily big so that it takes large fluid volume to measure the thermal conductivity. To dramatically reduce this fluid volume, a new sensor fabrication and a data processing method are proposed in this article. Contrast to the conventional and most popular two wire sensor, the new sensor system is made up of divided multiple long and short wires. Through validation experiments, it is found that the measured thermal conductivities of the glycerin are exactly same each other between the conventional and proposed new method. Also some technical considerations in arranging the multiple wires are briefly discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.122-122
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• 2011

HgCdTe는 고성능 적외선 센서 재료로 널리 사용되고 있다. 현재 상용화된 HgCdTe 소재는 통상적으로 액상 에피 성장법으로 제조 되고 있다. 액상 에피 성장법에 의해 제조된 HgCdTe는 갓 성장 상태에서 많은 양의 Hg-공공(vacancy)을 함유하게 되며 적외선 소자의 응용을 위해서는 이러한 Hg-공공을 채우기 위한 Hg-분위기 열처리 공정을 거치게 된다. 열처리 혹은 성장 공정 시 HgCdTe 소재 내에 발생하는 마이크로 혹은 나노스케일의 조성의 변화는 응력의 집중을 가져오며 이는 전자, 혹은 정공의 응집을 가져와 소자 동작의 불균일성을 야기한다. 본 연구에서는 액상 에피 성장법으로 성장 된 HgCdTe 박막내에 존재하는 응력의 분포와 Hg-공공을 채우기 위한 열처리 과정에서 생성 또는 소멸되는 응력의 변화를 Geometric phase strain 분석법으로 관찰하였다. 분석결과, 응력의 집중된 부분은 주로 성장 시 석출된 Te 및 Hg-공공으로 부터 기인함을 확인하였다. Hg-분위기 열처리를 통하여 석출된 Te 제거 및 Hg-공공의 감소를 확인하였고 이에 따른 응력의 집중 부분도 해소됨을 알 수 있었다.

• Journal of Powder Materials
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• v.19 no.4
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• pp.297-303
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• 2012

In this study, voltammetry system for realizing high sensitivity nano-labeled sensor of detecting heavy metals was designed, and optimal system operating conditions were determined. High precision digital to analog converter (DAC) circuit was designed to control applied unit voltage at working electrode and analog to digital converter (ADC) circuit was designed to measure the current range of $0.1{\sim}1000{\mu}A$ at counter electrode. Main control unit (MCU) circuit for controlling voltammetry system with 150 MHz clock speed, main memory circuit for the mathematical operation processing of the measured current value and independent power circuit for analog/digital circuit parts to reduce various noise were designed. From result of voltammetry system operation, oxidation current peaks which are proportional to the concentrations of Zn, Cd and Pb ions were found at each oxidation potential with high precision.

• Ceramist
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• v.21 no.2
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• pp.38-48
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• 2018

This paper reports a comprehensive review of the state-of-the-art in research on the enhancement of sensing properties for the detection of gases in exhaled breath. Daily health monitoring and early diagnosis of specific diseases via the analysis of exhaled breath is possible. Because biomarkers in exhaled breath are emitted in a very small amount, it is necessary to develop highly sensitive gas sensors. In recent years, a number of researches have been carried out using various strategies for the enhancement of sensing properties such as doping, catalyst, hollow sphere, heterojunction, size effect. We introduced each strategy and summarized recent progress on sensing properties for detection of biomarkers in exhaled breath.

• Ceramist
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• v.22 no.1
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• pp.96-106
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• 2019

Semiconducting carbon-based nanomaterials including single-walled carbon nanotubes(SWCNTs), multi-walled CNT(MWCNTs), graphene(GR), graphene oxide(GO), and reduced graphene oxide(RGO), are very promising sensing materials due to their large surface area, high conductivity, and ability to operate at room temperature. Despite of these advantages, the semiconducting carbon-based nanomaterials intrinsically possess crucial disadvantages compared with semiconducting metal oxide nanomaterials, such as relatively low gas response, irreversible recovery, and poor selectivity. Therefore, in this paper, we introduce a variety of strategies to overcome these disadvantages and investigate principle parameters to improve gas sensing performances.