• Biotechnology and Bioprocess Engineering:BBE
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• 제9권2호
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• pp.132-136
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• 2004

The LAL (Limulus amebocyte lysate) test for the detection and quantification of endotoxin is based on the gelation reaction between endotoxin and LAL from a blood extract of Limulus polyphemus. The test is labor intensive, requiring dedicated personnel, a relatively long reaction time (approximately 1 h), relatively large volumes of samples and reagents and the detection of the end-point is rather subjective. To solve these problems, a miniaturized LOC (lab-on-a-chip) prototype, 62mm (L) ${\times}$ 18 mm (W), was fabricated using PDMS (polydimethylsiloxane) bonded to glass. Using this prototype, in which 2mm (W) ${\times}$ 44.3mm (L) ${\times}$ 100 $\mu\textrm{m}$ (D) microfluidic channel was constructed, turbidometric and chromogenic assay detection methods were compared, and the chromogenic method was found the most suitable for a small volume assay. In this assay, the kinetic-point method was more accurate than the end-point method. The PDMS chip thickness was found to be minimized to around 2 mm to allow sufficient light transmittance, which necessitated the use of a glass slide bonding for chip rigidity. Due to this miniaturization, the test time was reduced from 1 h to less than 10 min, and the sample volume could be reduced from 100 to ca. 4.4 ${\mu}$L. In summation, this study suggested that the LOC using the LAL test principle could be an alternative as a semi-automated and reliable method for the detection of endotoxin.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2002년도 추계학술대회 논문집
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• pp.49-50
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• 2002

In micro-channels, the electro-viscous effect is caused by the electrical double layer on pressure-driven liquid flow. Velocity fields of flow inside micro-channels were measured using micro-PIV system for investigating the electro-viscous effect. De-ionized water and aqueous NaCl solutions with four different concentrations were used as working fluid in a PDMS micro-channel of $100{\mu}m$ width and $66{\mu}m$ height. The pressure gradient, dP/dx, was determined from the pre-determined input flow rate Q of syringe pump. The mean velocity $u_m$ used for calculating Reynolds number was obtained from the PIV velocity field data. These are used to plot the pressure gradient as a function of Reynolds numbers. The pressure gradient far lower concentration solution $(10^{-5}\;M)$ was higher than that for the higher concentration solution. The increase of flow resistance was about $30\%\;and\;37.5\%$ at Re=0.02 and 0.06, respectively.

• 한국식품영양학회지
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• 제16권4호
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• pp.372-378
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• 2003

SDE 및 SPME를 이용하여 계피로부터 추출한 휘발성 향기성분을 GC/MSD 분석한 결과 terpenes 20종, alcohol 3종, carbonyl 5종, esters 2종으로 총 30개의 휘발성 성분을 확인하였다. 이들 중 trans-cinnamaldehyde (86.4%), cis-cinnamaldehyde(0.9％), hydrocinnamaldehyde (0.1%) 등의 carbonyl 화합물이 peak area% 기준으로 약 88.2%로 계피 중 대부분을 차지하는 것으로 나타났다. 또한 식물체의 향기성분 분석에 많이 이용되는 SPME fiber 4종류를 비교 분석한 결과 terpen류 화합물들은 PDMS fiber에서 추출효율이 가장 좋았으며, cinnamyl alcohol과 같은 다소 극성인 화합물의 경우 DVB/CAR/PDMS fiber와 PA fiber에서 추출 효율이 가장 좋은 것으로 나타났다. SPME법에서 최적 조건을 설정하기 위해 추출온도와 추출시간을 달리하면서 비교 분석한 결과 copaene, murolene, cadinene, cis-cinnamaldehyde 등의 area% 값은 온도와 시간이 커질수록 증가한 반면에 trans-cinnamaldehyde의 area% 값은 감소하였다.

• 센서학회지
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• 제28권4호
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• pp.205-215
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• 2019

A flexible polyvinylidene fluoride (PVDF)/polydimethylsiloxane (PDMS) composite prototype with high piezoelectricity and force sensitivity was constructed, and its huge potential for applications such as biomechanical energy harvesting, self-powered health monitoring system, and pressure sensors was proved. The crystallization, piezoelectric, and electrical properties of the composites were characterized using an X-ray diffraction (XRD) experiment and customized experimental setups. The composite can sustain up to 100% strain, which is a huge improvement over monolithic PVDF fibers and other PVDF-based composites in the literature. The Young's modulus is 1.64 MPa, which is closely matched with the flexibility of the human skin, and shows the possibility for integrating PVDF/PDMS composites into wearable devices and implantable medical devices. The $300{\mu}m$ thick composite has a 14% volume fraction of PVDF fibers and produces high piezoelectricity with piezoelectric charge constants $d_{31}=19pC/N$ and $d_{33}=34pC/N$, and piezoelectric voltage constants $g_{31}=33.9mV/N$ and $g_{33}=61.2mV/N$. Under a 10 Hz actuation, the output voltage was measured at 190 mVpp, which is the largest output signal generated from a PVDF fiber-based prototype.

• 센서학회지
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• 제23권3호
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• pp.165-169
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• 2014

An existing infrared (IR) analysis system is generally composed of infrared source, IR focusing lenses, IR detector, and optical chopper. An optical chopper is widely used in combination with lock-in amplifier to improve the signal-to-noise ratio by periodically interrupting incident light beam. During recent years, a few researches on miniaturized optical chopper have been reported to apply to micro-scaled optical systems. In this paper, a micro optical chopper operated by electromagnetic actuation is proposed and applied to a miniaturized micro-scaled optical system operating in IR spectral range. Additionally, the fabrication method of the proposed micro chopper is demonstrated. The proposed micro optical chopper is composed of the polydimethylsiloxane (PDMS) membrane, solenoid, and permanent magnet. The permanent magnet is bonded on the PDMS membrane using an ultraviolet-activated adhesive. The operation of the chopper is based on the attractive and repulsive forces between permanent magnet and solenoid induced by an electrical current flowing through the solenoid. The fabricated micro optical chopper could operate up to 200 Hz of frequency. The maximum operating distance of the chopper with 7mm diameter membrane was $750{\mu}m$ at 100 Hz of frequency.

• 대한기계학회논문집B
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• 제30권3호
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• pp.255-261
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• 2006

Flow characteristics of DI water in a microchannel with a stenosis were investigated using .a micro PIV system with varying flow rate. The width and depth of the PDMS micro-channel were $100{\mu}m\;and\;50{\mu}m$, respectively. To Investigate flow characteristics in the micro-stenosis, the same experiment was carried out in a straight microchannel under the same flow rate. The measured mean velocity fields were almost symmetric with respect to the channel centerline. The experimental results are well agreed with the theoretical Hagen-Poiseuille profile. In the contraction part of the micro-stenosis, the oncoming flow is accelerated rapidly and the maximum velocity occurs at the throat, almost 4.99 time faster than that without the stenosis.

• 한국물환경학회지
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• 제26권4호
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• pp.622-628
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• 2010

In this study, Solid-phase microextraction (SPME) with GC/FID was studied as a possible alternative to liquid-liquid extraction for the analysis of BTEX and MTBE. Experimental parameters affecting the SPME process (such as kind of fibers, adsorption time, desorption time, volume ratio of sample to headspace, salt addition, and magnetic stirring) were optimized. Experimental parameters such as CAR/PDMS, adsorption time of 20 min, desorption time of 5 min at $250^{\circ}C$, headspace volume of 50 mL, sodium chloride (NaCl) concentration of 25% combined with magnetic stirring were selected in optimal experimental conditions for analysis of BTEX and MTBE. The general affinity of analytes to CAR/PDMS fiber was high in the order p-Xylene>Toluene>Ethylbenzene>MTBE>Benzene. The linearity of $R^2$ for BTEX and MTBE was from 0.970 to 0.999 when analyte concentration ranges from $30{\mu}g/L$ to $500{\mu}g/L$, respectively. The relative standard deviation (% RSD) were from 2.5% to 3.2% for concentration of $100{\mu}g/L$ (n=5), respectively. Finally, the limited of detection (LOD) observed in our study for BTEX and MTBE were from $7.5{\mu}g/L$ to $15{\mu}g/L$, respectively.

• 분석과학
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• 제24권2호
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• pp.119-126
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• 2011

국내 시중에 유통되어 음용되고 있는 먹는 샘물(생수) 30 종과 가정으로 공급되는 수돗물 9종 중의 벤젠, 톨루엔, 에틸벤젠, 자일렌을 고체상미량추출법을 사용하여 정량하였다. 정지상은 $100\;{\mu}m$ PDMS fiber를 이용하였고, 실험조건은 실온에서, 교반시간 1200 RPM G, 흡착시간 4 분, 탈착시간 1 분 이었다. 정량은 표준검량선법을 사용하였다. 평균검출한계는 벤젠 0.39 (${\pm}0.04$) ng/mL, 톨루엔 0.08 (${\pm}0.04$) ng/mL, 에틸벤젠 0.04 (${\pm}0.01$) ng/mL, o-자일렌 0.05 (${\pm}0.02$) ng/mL 이었다. 30 종의 먹는 샘물(생수)조사 결과 벤젠과 o-자일렌은 모든 시료에서 검출되지 않았으며, 톨루엔의 경우는 11 개의 시료, 에틸벤젠은 3 개의 시료에서 검출되었다. 검출된 물질의 각각의 농도범위는 $0.24({\pm}0.09)\sim2.95\;({\pm}0.08)\;ng/mL$, $0.08({\pm}0.06)\sim0.93({\pm}0.10)\;ng/mL$였다.

• 대한전자공학회논문지SD
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• 제47권2호
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• pp.7-14
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• 2010

본 논문에서는 금속 전극을 미세접촉인쇄방식으로 Ag ink를 이용하여 제작하는데 있어서 접착속도, 분리속도, 접촉시간의 세 가지의 동역학적 파라미터가 잉크 전이율에 미치는 영향을 분석하여 최적의 공정조건을 도출하였다. 잉킹공정에서는 접촉속도는 1 mm/s 이하, 접촉 후 유지시간은 짧게 하며, 분리속도는 1000 mm/s로 빠르게 해야 잉크의 전이율이 98%이상 높았다. 프린팅 공정에서는 반대로 접촉속도는 100mm/s 이상의 빠르게, 접촉 후 유지시간은 30초 이상, 분리속도는 1mm/s 이하로 느리게 할 때 최고의 인쇄특성을 보였다. 이를 이용해 전체 $5cm{\times}5cm$ 면적에 최소 선폭 $30{\mu}m$, 두께는 300~500nm, 50nm이하의 약 $15{\sim}16{\mu\Omega\cdot}cm$ 비저항을 가지는 전극을 인쇄하였다.

• Bulletin of the Korean Chemical Society
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• 제30권3호
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• pp.595-598
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• 2009

The authors describe an analytical method to determine total chlorine in a sanitizer liquid, incorporating a lab-made He-rf-plasma within a PDMS polymer microchip. Helium was used instead of Ar to produce a plasma to achieve efficient Cl excitation. A quartz tube 1 mm i.d. was embedded in the central channel of the polymer microchip to protect it from damage. Rotational temperature of the He-microchip plasma was in the range 1350-3600 K, as estimated from the spectrum of the OH radical. Chlorine was generated in a volatilization reaction vessel containing potassium permanganate in combination of sulfuric acid and then introduced into the polymer microchip plasma (PMP). Atomic emission lines of Cl at 438.2 nm and 837.7 nm were used for analysis; no emission was observed for Ar plasma. The achieved limit of detection was 0.81 ${\mu}g\;mL^{-1}$ (rf powers of 30-70 W), which was sensitive enough to analyze sanitizers that typically contained 100-200 ${\mu}g\;mL^{-1}$ of free chlorine in chlorinated water. This study demonstrates the usefulness of the devised PMP system in the food sciences and related industries.