• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.552-552
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• 2012

We fabricated reduced graphene oxide field-effect transistor (RGO-FET) on glass for highly sensitive temperature and IR detection. The device has the channels of RGO responsive to physical stimuli such as temperature and IR. The RGO sensing layers are fabricated from exfoliated graphene oxide sheets that are deposited to form a thin continuous network by electrostatic assembly. These graphene oxide networks are reduced toward reduce graphene oxide by exposure to a hydrazine hydrate vapor. To improve performance and eliminate interferences from oxygen and water vapor absorption to electrical properties of RGO-FET, the sensor devices were encapsulated by the tetratetracontane layer after annealing treatment. The device with encapsulation layer showed lower hysteresis, improved stability, and better repeatability. The temperature response of RGO-FET is examined by measuring changing the temperature, the device exhibited the high sensitivity and repeatability even with the temperature interval of 1 K. We also demonstrated that our devices have capability of IR sensing.

• Journal of the Korean Ceramic Society
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• v.37 no.8
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• pp.817-823
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• 2000

A solid-state electrochemicall cell for sensing CO2 gas was fabricated using a solid electrolyte of Li2CO3-Li3PO4-Al2O3 mixture and a reference electrode of LiMn2O4. The e.m.f. (electromotive force) of sensor showed a good accordance with theoretical Nernst slope (n=2) for CO2 gas concentration range of 100-10000 ppm above 35$0^{\circ}C$. The e.m.f. of sensor was constant regardless of oxygen partial pressure at the high temperature above 0.1 atm. It was, however, a little depended on oxygen partial pressure as the pressure decreased below 0.1 atm. The oxygen-dependency of our sensor gradually disappeared as the operating temperature increased. The sensing behavior of our CO2 sensor was affected by the presence of water vapor, but its effect was small comparing with other sensors.

• Journal of the Korean Vacuum Society
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• v.17 no.5
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• pp.448-454
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• 2008

The purpose of this paper is to discuss the fabrication of $\beta$-PVDF($\beta$-Polyvinylidene fluoride, ${\beta}-PVF_2$) organic thin films through the vapor deposition method and to investigate the piezoelectric properties of the organic thin films produced. Vapor deposition was performed under the following conditions : the temperature of evaporator, the applied electric field and the pressure of reaction chamber were $270^{\circ}C$, 142.4 kV/cm and $2.0{\times}10^{-5}Torr$, respectively. The results showed that the amount of $\beta$-form PVDF increased from 72 % to 95.5 % with an increase in the substrate temperature. In the case of a sensor response characteristic by varying the force moment from $1.372{\times}10^{-5}N{\cdot}m$ to $39.2{\times}10^{-5}N{\cdot}m$, the output voltage increased from 1.39V to 7.04V.

• Journal of Sensor Science and Technology
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• v.14 no.2
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• pp.69-77
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• 2005

The electronic nose (e-nose) has been used in food industry and quality controls in plastic packaging. Recently it finds its applications in medical diagnosis, specifically on detection of diabetes, pulmonary or gastrointestinal problem, or infections by examining odors in the breath or tissues with its odor characterizing ability. Moreover, the use of portable e-nose enables the on-site measurements and analysis of vapors without extra gas-sampling units. This is expected to widen the application of the e-nose in various fields including point-of-care-test or e-health. In this study, a PDA-based portable e-nose was developed using micro-machined gas sensor array and miniaturized electronic interfaces. The rich capacities of the PDA in its computing power and various interfaces are expected to provide the rapid and application specific development of the diagnostic devices, and easy connection to other facilities through information technology (IT) infra. For performance verification of the developed portable e-nose system, Six different vapors were measured using the system. Seven different carbon-black polymer composites were used for the sensor array. The results showed the reproducibility of the measured data and the distinguishable patterns between the vapor species. Additionally, the application of two typical pattern recognition algorithms verified the possibility of the automatic vapor recognition from the portable measurements. These validated the portable e-nose based on PDA developed in this study.

• ETRI Journal
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• v.35 no.4
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• pp.566-570
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• 2013

In this paper, we demonstrate the capabilities of 380-nm ultraviolet (UV) light-emitting diodes (LEDs) using metal organic chemical vapor deposition. The epi-structure of these LEDs consists of InGaN/AlGaN multiple quantum wells on a patterned sapphire substrate, and the devices are fabricated using a conventional LED process. The LEDs are packaged with a type of surface mount device with Al-metal. A UV LED can emit light at 383.3 nm, and its maximum output power is 118.4 mW at 350 mA.

• Advances in aircraft and spacecraft science
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• v.2 no.3
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• pp.263-273
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• 2015

Carbon nanotube strain sensors, or so called "fuzzy fiber" sensors have not yet been studied sufficiently. These sensors are composed of a bundle of fiberglass fibers coated with CNT through a thermal chemical vapor deposition process. The characteristics of these fuzzy fiber sensors differ from a conventional nanocomposite in that the CNTs are anchored to a substrate fiber and the CNTs have a preferential orientation due to this bonding to the substrate fiber. A numerical model was constructed to predict the strain response of a composite with embedded fuzzy fiber sensors in order to compare result with the experimental results obtained in an earlier study. A comparison of the numerical and experimental responses was conducted based on this work. The longitudinal sensor output from the model matches nearly perfectly with the experimental results. The transverse and off-axis tests follow the correct trends; however the magnitude of the output does not match well with the experimental data. An explanation of the disparity is proposed based on microstructural interactions between individual nanotubes within the sensor.

• Korean Journal of Human Ecology
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• v.8 no.1
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• pp.151-163
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• 1999

The purpose of this study was to investigate the thermal resistance and the liquid/vapor water transfer characteristics of four waterproof and water vapor permeable coated fabrics with the ground fabric called nylon taffeta. In order to establish the experimental environment, outdoor temperature and humidity in Taegu during the last three years were examined and the experiment was performed at (1) $15^{\circ}C$, 50% R.H., (2) $20^{\circ}C$, 60% R.H., (3) $25^{\circ}C$, 65% R.H., which were the average standards in spring and fall. The test results were as follows ; 1. Among physical parameters, the thinner the thickness was, the higher the water vapor permeability was. But the porosity in thickness was not proportional to water vapor permeability linearly. 2. The thicker the thickness of specimens was and the smaller the bulk density and porosity were, the higher the thermal resistance. And the results also shown that the larger the temperature difference between the environmental temperature and the hot plate was, the more the difference of CLO values was apparent. 3. Since the contact angle of all specimens are above $90^{\circ}$, the all specimens have a good performance in waterproof. The more the specimens surface were rough, the higher the thermal resistance was. 4. According to the result of performing moisture transfer test using the simulating body skin-clothing-environment system, the humidity sensor placed in between the fabric and the environment detected the full saturation in 10 minutes after the experiment had began at $15^{\circ}C$, 50% R.H. and in 15 minutes after the experiment both at $20^{\circ}C$, 60% R.H. and at $25^{\circ}C$, 65% R.H. 5. ${\Delta}$ values of the humidity sensors placed in between the human body and the fabric and in between the fabric and the environment fluctuated repeatedly within the range of $20{\sim}40%$ at $20^{\circ}C$, 60% R.H., and $15{\sim}30%$ at $25^{\circ}C$, 65% R.H.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.3
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• pp.583-589
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• 2016

Volatile organic compounds(VOCs) are regarded as a harmful cause substance not only causing air pollutions but also causing global warming phenomenon. For this reason, VOCs are managed politically to reduce emissions by each country. In particular, the vapor from the gas station contains VOCs which is harmful to the human body such as carcinogens benzene and pollute the atmosphere, the Ministry of Environment defined every gas station must install vapor recovery equipment to recover volatile organic compounds. Recently, there are many accidents caused by existing vapor treatment methods, the liquefaction recovery technology is getting the spotlight to cool the vapor at the field. However, because the liquefaction recovery technology have risks of fire or explosion in accordance with temperature, the real time monitoring is critical factor. In this paper, we implement an Android-based monitoring application for liquified vapor recovery device which attached sensor module for temperature and power to monitoring real time information.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.272-272
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• 2014

SnO thin films, 100 nm in thickness, were deposited on glass substrates by RF magnetron sputtering. A stack structure of $SnO_2/SnO$, where few nanometers of $SnO_2$ were determined on the SnO thin film by X-ray photoelectron spectroscopy. In addition, XPS depth profile analysis of the pristine and heat treated thin films were introduced. The electrical behavior of the as-sputtered films during the annealing was recorded to investigate the working conditions for the SnO sensor. Subsequently, The NH3 sensing properties of the SnO sensor at operating temperature of $50-200^{\circ}C$ were examined, in which the p-type semiconducting sensing properties of the thin film were noted. The sensor shows good sensitivity and repeatability to $NH_3$ vapor. The sensor properties toward several gases like $H_2S$, $CH_4$ and $C_3H_8$ were also introduced. Finally, a sensing mechanism was proposed and discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.401-401
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• 2014

In this study, graphene, the most attractive material today, has been applied to the wavelength-modulated surface plasmon resonance (SPR) sensor. The optical fiber sensor technology is the most fascinating topic because of its several benefits. In addition to this, the SPR phenomenon enables the detection of biomaterials to be label-free, highly sensitive, and accurate. Therefore, the optical fiber SPR sensor has powerful advantages to detect biomaterials. Meanwhile, Graphene shows superior mechanical, electrical, and optical characteristics, so that it has tremendous potential to be applied to any applications. Especially, grapheme has tighter confinement plasmon and relatively long propagation distances, so that it can enhance the light-matter interactions (F. H. L. Koppens, et al., Nano Lett., 2011). Accordingly, we coated graphene on the optical fiber probe which we fabricated to compose the wavelength-modulated SPR sensor (Figure 1.). The graphene film was synthesized via thermal chemical vapor deposition (CVD) process. Synthesized graphene was transferred on the core exposed region of fiber optic by lift-off method. Detected analytes were biotinylated double cross-over DNA structure (DXB) and Streptavidin (SA) as the ligand-receptor binding model. The preliminary results showed the SPR signal shifts for the DXB and SA binding rather than the concentration change.