• Food Science and Biotechnology
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• v.16 no.3
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• pp.337-342
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• 2007

Conventional methods for pathogen detection and identification are labor-intensive and take days to complete. Biosensors have shown great potential for the rapid detection of foodborne pathogens. Fiber-optic biosensors have been used to rapidly detect pathogens because they can be very sensitive and are simple to operate. However, many fiber-optic biosensors rely on manual sensor handling and the sandwich assay, which require more effort and are less sensitive. To increase the simplicity of operation and detection sensitivity, a binding inhibition assay method for detecting Listeria monocytogenes in food samples was developed using an automated, fiber-optic-based immunosensor: RAPTOR (Research International, Monroe, WA, USA). For the assay, fiber-optic biosensors were developed by the immobilization of Listeria antibodies on polystyrene fiber waveguides through a biotin-avidin reaction. Developed fiber-optic biosensors were incorporated into the RAPTOR to evaluate the detection of L. monocytogenes in frankfurter samples. The binding inhibition method combined with RAPTOR was sensitive enough to detect L. monocytogenes ($5.4{\times}10^7\;CFU/mL$) in a frankfurter sample.

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.89-91
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• 2003

The determination of DNA hybridization reaction can apply the molecular biology research, clinic diagnostics, bioengineering, environment monitoring, food science and other application area. So, the improvement of DNA detection system is very important for the determination of this hybridization reaction. In this study, we report the characterization of the probe and target oligonucleotide hybridization reaction using the evanescent field microscopy. First, we have fabricated DNA chip microarray. The particles which were immobilized oligonucleotides were arranged by the random fluidic self-assembly on the pattern chips, using hydrophobic interaction. Second, we have detected DNA hybridization reaction using evanescent field microscopy. The 5'-biotinylated probe oligonucleotides were immobilized on the surface of DNA chip microarray and the hybridization reaction with the Rhodamine conjugated target oligonucleotide was excited fluorescence generated on the evanescent field microscopy. In the foundation of this result, we could be employed as the basis of a probe olidonucleotide, capable of detecting the target oligonucleotide and monitoring it in a large analyte concentration range and various mismatching condition.

• Bulletin of the Korean Chemical Society
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• v.32 no.9
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• pp.3400-3404
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• 2011

A new rhodamine B-coumarin conjugate (1) capable of recognizing both $Cu^{2+}$ and $Fe^{3+}$ using two different detection modes have been designed and synthesized. The metal ion induced optical changes of 1 were investigated in $CH_3CN-H_2O$ (1:1, v/v, HEPES 50 mM, pH = 7.0) solution. Sensor 1 exhibits selective colorimetric recognition of $Cu^{2+}$ and fluorescent recognition of $Fe^{3+}$ with UV-vis and fluorescence spectroscopy, respectively. Moreover, both of the $Cu^{2+}$ and $Fe^{3+}$ recognition processes are observed to be barely interfered by other coexisting metal ions.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1219-1220
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• 2015

마이크로, 나노유체 (micro-, nanofluidics)을 이용한 종이 기반 분석 소자 (paper-based analytical devices, micro-PADs)에 대한 관심이 증가하고 있다. 종이 기반의 분석 소자는 초저가의 비용과 간단한 공정 방법으로 인하여 상용화 컨셉의 바이오센서로 각광받고 있다. 하지만, 종이 기반의 분석 소자는 낮은 검출 한계 (limit of detection, LOD)와 민감도 (sensitivity)의 제한이 있다. 그로 인해 우리는 이온 선택적 투과층 (ion permselective membrane, i.e. Nafion)을 종이 기반의 분석 소자와 결합하여 이온 농도 분극 (ion concentration polarization, ICP) 현상을 구현하여 낮은 검출한계와 민감도를 개선할 수 있었다. 접착력이 있는 테이프 표면에 이온 선택적 투과층을 패터닝 (patterning)하여 종이 기반 분석 소자와 결합하여 매우 간단하게 소자를 제작할 수 있었다. 따라서 종이 기반의 채널 양단에 직류 전압을 인가했을 때 발생하는 ICP 현상으로 인하여 형광 물질 (fluorescence dye)이 농축(preconcentration)되는 것을 확인할 수 있었다. 구체적으로, 초기 농도가 1.55 nM인 형광 물질을 이용하여 200 V의 외부전압을 인가했을 때, 500 초 이내에 1000 배 이상의 농축비를 얻을 수 있었다. 따라서, 외부 전압을 상용화된 건전지 출력값으로 낮출 수 있다면 다양한 종이 기반 분석 소자와 간단한 결합 방법을 통해 상용화 컨셉의 바이오센서로도 구현이 가능할 것이다.

• Textile Coloration and Finishing
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• v.20 no.1
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• pp.8-15
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• 2008

We presented the modified decal-transfer lithography (DTL) and light stamping lithography (LSL) as new powerful methods to generate patterns of poly(dimethylsiloxane) (PDMS) on the substrate. The microstructures of PDMS fabricated by covalent binding between PDMS and substrate had played as barrier to locally control wettability. The transfer mechanism of PDMS is cohesive mechanical failure (CMF) in DTL method. In the LSL method, the features of patterned PDMS are physically torn and transferred onto a substrate via UV-induced surface reaction that results in bonding between PDMS and substrate. Additionally we have exploited to generate the patterning of rhodamine B and quantum dots (QDs), which was accomplished by hydrophobic interaction between dyes and PDMS micropatterns. The topological analysis of micropatterning of PDMS were performed by atomic force microscopy (AFM), and the patterning of rhodamine B and quantum dots was clearly shown by optical and fluorescence microscope. Furthermore, it could be applied to surface guided flow patterns in microfluidic device because of control of surface wettability. The advantages of these methods are simple process, rapid transfer of PDMS, modulation of surface wettability, and control of various pattern size and shape. It may be applied to the fabrication of chemical sensor, display units, and microfluidic devices.

• ETRI Journal
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• v.29 no.5
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• pp.667-669
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• 2007

This letter presents a smart integrated microfluidic device which can be applied to actively immobilize proteins on demand. The active component in the device is a temperature-controllable microelectrode array with a smart polymer film, poly(N-isopropylacrylamide) (PNIPAAm) which can be thermally switched between hydrophilic and hydrophobic states. It is integrated into a micro hot diaphragm having an integrated micro heater and temperature sensors on a 2-micrometer-thick silicon oxide/silicon nitride/silicon oxide (O/N/O) template. Only 36 mW is required to heat the large template area of 2 mm${\times}$16 mm to $40^{\circ}C$ within 1 second. To relay the stimulus-response activity to the microelectrode surface, the interface is modified with a smart polymer. For a model biomolecular affinity test, an anti-6-(2, 4-dinitrophenyl) aminohexanoic acid (DNP) antibody protein immobilization on the microelectrodes is demonstrated by fluorescence patterns.

• The Korean Journal of Physiology and Pharmacology
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• v.23 no.4
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• pp.237-249
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• 2019

Confirming the direct link between neural circuit activity and animal behavior has been a principal aim of neuroscience. The genetically encoded calcium indicator (GECI), which binds to calcium ions and emits fluorescence visualizing intracellular calcium concentration, enables detection of in vivo neuronal firing activity. Various GECIs have been developed and can be chosen for diverse purposes. These GECI-based signals can be acquired by several tools including two-photon microscopy and microendoscopy for precise or wide imaging at cellular to synaptic levels. In addition, the images from GECI signals can be analyzed with open source codes including constrained non-negative matrix factorization for endoscopy data (CNMF_E) and miniscope 1-photon-based calcium imaging signal extraction pipeline (MIN1PIPE), and considering parameters of the imaged brain regions (e.g., diameter or shape of soma or the resolution of recorded images), the real-time activity of each cell can be acquired and linked with animal behaviors. As a result, GECI signal analysis can be a powerful tool for revealing the functions of neuronal circuits related to specific behaviors.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.2
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• pp.130-134
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• 2019

In this paper, a laser-based non-contact load cell is newly developed for measuring forces in prestressed concrete tendons. First, alumina particles have been sprayed onto an empty load cell which has no strain gauges on it, and the layer has been used as a passive stress sensor. Then, the spectral shifts in fluorescence spectroscopy have been measured using a laser-based spectroscopic system under various force levels, and it has been found that the relation of applied force and spectral shift is linear in a lab-scale test. To validate the field applicability of the customized load cell, a full-scale prestressed concrete specimen has been constructed in a yard. During the field test, it was, however, found that the coating surface has irregular stress distribution. Therefore, the location of a probe has to be fixed onto the customized load cell for using the coating layer as a passive stress sensor. So, a prototype customized load cell has been manufactured, which consists of a probe mount on its casing. Then, by performing lab-scale uniaxial compression tests with the prototype load cell, a linear relation between compression stress and spectrum shift at a specific point where laser light had been illuminated has been detected. Thus, it has a high possibility to use the prototype load cell as a force sensor of prestressed concrete tendons.

• Journal of Bio-Environment Control
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• v.28 no.4
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• pp.461-470
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• 2019

This study was carried out to quantify the drought stress in grafted watermelon seedlings non-destructively by using chlorophyll fluorescence (CF) imaging technique rather than the visual judgment. Six-day old watermelon seedlings were grown under uniform irrigation for 3 days, and then given drought stress. Afterward, the sensor for the measurement of water content in plug tray cell unit was used to classify the drought-stress level into nine groups from D1 (53.0%, sufficient moisture state) to D9 (15.7%, extremely dry stress), and the 16 CF parameters were measured. In addition, re-irrigation was performed on the drought stressed seedlings(D5 - D9) to determine the growth and photosynthesis recovery level, which was not confirmed by visual judgment. The kinetic curve patterns of CF in three different drought stressed seedling groups were found to be different for the early detection of drought stress. All the 16 CF parameters decreased continuously with exposure to drought stress and drastically decreased from D5 (32.1%) where the visual judgment was possible. The fluorescence decline ratio (Rfd_Lss) started to decrease from the initial drought stress level (D5 - D6), and the Maximum PSII quantum yield (Fv/Fm) was significantly decreased in the later extreme drought stress range (D7 - D9) by re-irrigation recovery test. Thus, Rfd_Lss and Fv/Fm parameters were finally selected as potent indicators of growth and photosynthesis recovery in the initial and later stages of drought stress. Also, to the differences in the numerical values of the individual chlorophyll fluorescence parameters, the drought stress level was intuitively confirmed through the image. These results indicate that Rfd and Fv/Fm can be considered as potential CF parameters for the detection of low and extremely high drought stress, respectively. Furthermore, Fv/Fm can be considered as the best CF parameters for recovery at re-irrigation.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.74-78
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• 2003

Multi-channel images of 11-MUA and 11-MUOH self-assembled monolayers were obtained by using two-dimensional surface plasmon resonance (SPR) absorption. Patterning process was simplified by exploiting direct photo-oxidation of thiol bonding (photolysis) instead of conventional photolithography. Sharper images were resolved by using a white light source in combination with a narrow bandpass filter in the visible region, minimizing the diffraction patterns on the images. The line profile calibration of the image contrast caused by different resonance conditions at each points on the sensor surface (at a fixed incident angle) enables us to discriminate the monolayer thickness in sub-nanometer scale. Furthermore, there is no signal degradation such as photo bleaching or quenching which are common in the detection methods based on the fluorescence.