• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.5
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• pp.227-231
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• 2005

We have developed a microsystem with a capillary electrophoresis (CE) and an electrochemical detector (ECD). The microfabricated CE-ECD systems are adequate for a disposable type and the characteristics are optimized for an application to the electrochemical detection. The system was realized with polydimethylsiloxane (PDMS)-glass chip and indium tin oxide electrode. The injection and separation channels (80 um wide$\ast$40 um deep) were produced by moulding a PDMS against a microfabricated master with relatively simple and inexpensive methods. A CE-ECD systems were fabricated on the same substrate with the same fabrication procedure. The surface of PDMS layer and ITO-coated glass layer was treated with UV-Ozone to improve bonding strength and to enhance the effect of electroosmotic flow. For comparing the performance of the ITO electrodes with the gold electrodes, gold electrode microchip was fabricated with the same dimension. The running buffer was prepared by 10 mM 2-(N-morpholino)ethanesulfonic acid (MES) titrated to PH 6.5 using 0.1 N NaOH. We measured olectropherograms for the testing analytes consisted of catechol and dopamine with the different concentrations of 1 mM and 0.1 mM, respectively. The measured current peaks of dopamine and catechol are proportional to their concentrations. For comparing the performance of the ITO electrodes with the gold electrodes, electropherograms was measured for CE-ECD device with gold electrodes under the same conditions. Except for the base current level, the performances including sensitivity, stability, and resolution of CE-ECD microchip with ITO electrode are almost the same compared with gold electrode CE-ECD device. The disposable CE/ECD system showed similar results with the previously reported expensive system in the limit of detection and peak skew. When we are using disposable microchips, it is possible to avoid polishing electrode and reconditioning.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1686-1687
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• 2011

A microfabricated chip with in-channel electrochemical cell using interdigitated gold electrode was fabricated for sensitive electrochemical analysis. The gold electrodes were fabricated on glass wafer using thermal evaporator and were covered using PDMS mold containing microchannel for analyte and electrolyte. The active area of each electrode was $250\;{\mu}m{\times}200\;{\mu}m$ with a gap of 200 ${\mu}m$ between the electrodes. Microelectrodes results in maximum amplification of signal, since the signal enhancement effect due to cycling of the reduced and oxidized species strongly depends on the inter electrode distance. Analytes such as methylene blue and guanosine were characterized using the fabricated electrodes and their electrochemical characteristics were compared with conventional bulk electrodes. The device so developed shall find use as disposable electrochemical cell for rapid and sensitive analysis of electroactive species.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.18 no.1
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• pp.116-121
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• 2009

Thermosonic flip chip bonding is an important technology for the electronic packaging due to its simplicity, cost effectiveness and clean and dry process. Mechanical properties of the horn and the shank, such as the natural frequency and the amplitude, have a great effect on the bonding capability of the transverse flip chip bonding system. In this research, two kinds of study are performed. The first is the new design of the clamp and the second is the effect of tolerance parameters to the performance of the system. The clamp with a bent shape is newly designed to hold the nodal point of the flip chip. The second is the effect of the design parameters on the vibration amplitude and planarity at the end of the shank. The variation of the tolerance parameters changes the amplitude and the frequency of the vibration of the shank. They, in turn, have an effect on the quantity of the plastic deformation of the gold ball bump, which determined the quality of the flip chip bonding. The tolerance parameters that give the great effect on the amplitude of the shank are determined using Taguchi's method. Error of set-up angle, the length and diameter of horn and error of the length of the shank are determined to be the parameters that have peat effect on the amplitude of the system.

• Korean Journal of Veterinary Service
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• v.30 no.4
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• pp.489-496
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• 2007

An oligonucleotide microarray system was developed for the simultaneous detection of porcine epidemic diarrhea virus, transmissible gastroenteritis virus, porcine enteric calicivirus, porcine group A and C rotavirus. RNAs of the reference viruses and porcine diarrhea samples were extracted and amplified using one-step multiplex RT-PCR in the presence of cyanine 5-dCTP and hybridized on the microarray chip that spotted the virus-specific oligonucleotides. This system were approximately 10-to 100-fold higher in sensitivity than conventional RT-PCR, and the assay time was less than 3 hours. The relative sensitivity and specificity were 92% and 72.2%, respectively, based on 102 porcine diarrhea samples using RT-PCR as gold standard. These results suggested that the oligonucleotide microarray system in this study be probably more reliable and reproducible means for detecting porcine enteric viruses and that it could be of substantial use in routine diagnostic laboratories.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.207-210
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• 2000

Properties of SrTiO$_3$ thin films were characterized under the influence of an applied dc voltage utilizing a gold resonator with a flip-chip capacitor. The measurements were performed at microwave frequency ranges and low temperatures cryogenic temperatures. The dielectric constant of 830 and the low loss tangent of 6X10$^{-3}$ at 3.64 GHz were observed at 90 K and 100 V. The quality in the SrTiO$_3$ film was presented in terms of fractional frequency under the bias voltages and cryogenic temperatures.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.05a
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• pp.65-70
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• 2006

In this study, a DNA chip with a microelectrode array was fabricated using microfabrication technology. Several probe DNAs consisting of mercaptohexyl moiety at their 5 end were immobilized on the gold electrodes by DNA arrayer. Then target DNAs were hybridized and reacted with Hoechst 33258, which is a DNA minor groove binder and electrochemically active dye. Linear sweep voltammetry or cyclic voltammetry showed a difference between target DNA and control DNA in the anodic peak current values. It was derived from Hoechst 33258 concentrated at the electrode surface through association with formed hybrid. It suggested that this DNA chip could recognize the sequence specific genes.

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.4
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• pp.221-226
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• 2003

With the current rapid development of nanotechnology and synthesis technology for designed oligonucleotides or oligonucleotide-modified nanoparticle conjugates, the combined strategies have become one of the most valuable methods in detection technology for DNA analysis. Using the uniquely recognizable interactions of pre-designed DNA molecules in assembling nanoparticles, various novel approaches have been recently developed towards detecting specific DNA sequences. Here we describe the key fundamentals and issues of this promising strategies ranging from the initial findings of rationally designed DNA-based assembly of nanoparticles to the extended chip-based detection system. Some limitations of these new strategies and possible approaches will be also discussed for the practical application in the area of DNA microarray detection.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.9
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• pp.749-755
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• 2007

Recently, novel MEMS probe cards can support reliable wafer level chip test with high density probing capacity. However, manufacturing cost and process complexity are crucial weak points for low cost mass production. To overcome these limitations, we have developed micro spring structured MEMS probe card. For fabrication of micro spring module, a wire bonder and electrolytic polished gold wires are used. In this case, stringent tension force control is essential to guarantee the low level contact resistance of micro spring for reliable probing performance. For this, relation between tension force of fabricated probe card and contact resistance is characterized. Compare to conventional probe cards, developed MEMS probe card requires fewer fabrication steps and it can be manufactured with lower cost than other MEMS probe cards. Also, due to the small contact scratch patterns, we expect that it can be applied to bumping types chip test which require higher probing density.

• Journal of fish pathology
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• v.27 no.2
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• pp.99-105
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• 2014

Biosensors consist of biochemical recognition agents like antibodies immobilized on the surfaces of transducers that change the recognition into a measurable electronic signal. Here we report a piezoelectric immunosensor made to detect Vibrio vulnificus. A 9MHz AT-cut piezoelectric wafer attached with two gold electrodes of 5mm diameter was used as the transducer of the QCM biosensor with a reproducibility of ${\pm}0.1Hz$ in frequency response. We have tried different approaches to immobilize antibody on the sensor chip. Concerning the orientation of antibody for the best antigen binding capacity, the antibody was immobilized by specific binding to protein G or by cross-linking through hydrazine. In addition, protein G was cross-linked on glutaraldehyde activated immine layer (PEI) or EDC/NHS activated sulfide monolayer (MPA). PEI was found to be more effective to immobilize protein G following glutaraldehyde activation than MPA. However, hydrazine chip showed a better capability to immobilize more IgG than protein G chip and a higher sensitivity. The sensor system was able to detect V. vulnificus in dose dependent manner and was able to detect bacterial cells within 5 minutes by monitoring frequency shifts in real time. The detection limit can be improved by preincubation to enrich the bacterial cell number.

• Transactions on Electrical and Electronic Materials
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• v.14 no.2
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• pp.63-66
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• 2013

This paper describes the highly productive process technologies of microprobe arrays, which were used for a probe card to test a Dynamic Random Access Memory (DRAM) chip with fine pitch pads. Cantilever-type microprobe arrays were fabricated using conventional micro-electro-mechanical system (MEMS) process technologies. Bonding material, gold-tin (Au-Sn) paste, was used to bond the Ni-Co alloy microprobes to the ceramic space transformer. The electrical and mechanical characteristics of a probe card with fabricated microprobes were measured by a conventional probe card tester. A probe card assembled with the fabricated microprobes showed good x-y alignment and planarity errors within ${\pm}5{\mu}m$ and ${\pm}10{\mu}m$, respectively. In addition, the average leakage current and contact resistance were approximately 1.04 nA and 0.054 ohm, respectively. The proposed highly productive microprobes can be applied to a MEMS probe card, to test a DRAM chip with fine pitch pads.