• Korea-Australia Rheology Journal
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• v.19 no.3
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• pp.109-115
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• 2007

A new microchip-based aggregometer that uses a stirring-aided disaggregation mechanism in a microchip was developed to measure red blood cell (RBC) aggregation in blood and RBC suspensions. Conventional methods of RBC disaggregation, such as the rotational Couette system, were replaced with a newly designed stirring-induced disaggregation mechanism. Using a stirrer in a microchip, the aggregated RBCs stored in a microchip can be easily disaggregated. With an abrupt halt of the stirring, the backscattered light intensity can be measured in a microchip with respect to time. The time recording of the backscattered light intensity (syllectogram) shows an exponential decreasing curve representing the RBC aggregation. By analyzing the syllectogram, aggregation indices such as AI and M were determined. The results showed excellent agreement with LORCA. The essential feature of this design is the incorporation of a disposable microchip and the stirring-induced disaggregation mechanism.

• Bulletin of the Korean Chemical Society
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• v.33 no.4
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• pp.1135-1140
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• 2012

An electrochromatographic microchip with carboxyl-group-derivatized mono-disperse silica packing was prepared from the corresponding colloidal silica solution by utilizing capillary action and self-assembly behavior. The silica beads in water were primed by the capillary action toward the ends of cross-patterned microchannel on a cyclic olefinic copolymer (COC) substrate. Slow evaporation of water at the front of packing promoted the self-assembled packing of the beads. After thermally binding a cover plate on the chip substrate, reservoirs for sample solutions were fabricated at the ends of the microchannel. The packing at the entrances of the microchannel was silver coated to fix utilizing an electroless silver-plating technique to prevent the erosion of the packed structure caused by the sudden switching of a high voltage DC power source. The electrochromatographic behavior of the microchip was explored and compared to that of the microchip with bare silica packing in basic borate buffer. Electrophoretic migration of Rhodamine B was dominant in the microchip with the carboxyl-derivatized silica packing that resulted in a migration approximated twice as fast, while the reversible adsorption was dominant in the bare silica-packed microchip. Not only the faster migration rates of the negatively charged FITC-derivatives of amino acids but also the different migration due to the charge interaction at the packing surface were observed. The electrochromatographic characteristics were studied in detail and compared with those of the bare silica packed microchip in terms of the packing material, the separation potential, pH of the running buffer, and also the separation channel length.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.6
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• pp.260-264
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• 2002

We developed LD Pumped Nd:$VVO_4$ microchip laser with the cavity length of 1mm. The microchip laser output was 87.5㎽ at the wavelength of 1063.9nm with the input power of 241㎽ at the wavelength of 809nm. The slope efficiency was 40.7% and the threshold input power was 31.1㎽. We have also defined input power limit for the single longitudinal mode operation theoretically. It was 2.5 times larger than that of threshold input intensity. According to the results of simulation, the Nd:YVO$_4$ microchip laser can be operated with the maximum output of 15㎽ for the single longitudinal mode up to the input power of 77.75㎽.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.12
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• pp.1115-1122
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• 2008

This paper presents a new microchip which can separate motile sperm by chemotaxis. The microchip was developed to create longitudinal concentration gradient in the microchannel due to diffusion. Linearly good concentration gradient of chemoattractant was generated without any fluid control devices. In sperm separation experiment with the developed microchip, mouse sperm was used as sample and acetylcholine was selected as chemoattractant. Human tubal fluid (HTF), buffer solution, was introduced into the microchannel of the microchip and attractants diluted in ratio of 1, 1/2, 1/4, 1/8, 1/16, 1/32 and 1/64 including control (DI water) were dropped in each outlet by $2\;{\mu}l$ volume with micropippet. After 5min, $1\;{\mu}l$ sperm solution was dropped into inlet of the chip. After 10 min, when sperms reached to the outlet by chemotaxis, we counted sperms in each outlet by using microscopy. Consequently, we could separate progressive motile sperm with the new microchip. In the experiment, the most sperms were isolated at the outlet dropped with 1/16 diluted solution. The optimal concentration gradient to induce chemotaxis was about 0.625 mg/ml/mm.

• Bulletin of the Korean Chemical Society
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• v.28 no.4
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• pp.553-556
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• 2007

We previously reported a 27.12 MHz inductively coupled plasma source at atmospheric pressure for atomic emission spectrometry based on polymer microchip plasma technology. For the PDMS polymer microchip plasma, molecular emission was observed, but no metallic detection was done. In this experiment, a lab-made electrothermal vaporizer (ETV) with tantalum coil was connected to the microchip plasma for aqueous sample introduction to detect metal ions. The electrode geometry of this microchip plasma was redesigned for better stability and easy monitoring of emission. The plasma was operated at an rf power of 30-70 W using argon gas at 300 mL/min. Gas kinetic temperatures between 800-3200 K were obtained by measuring OH emission band. Limits of detection of about 20 ng/mL, 96.1 ng/mL, and 1.01 μ g/mL were obtained for alkali metals, Zn, and Pb, respectively, when 10 μ L samples in 0.1% nitric acid were injected into the ETV.

• Bulletin of the Korean Chemical Society
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• v.30 no.3
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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.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.4
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• pp.181-187
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• 2005

In this study, a microchip system fabricated with MEMS technology was developed to detect bioelectrical signals. The developed microchip using the conductivity of gold nanoparticles could detect the biopotential with a high sensitivity. For designing the microchip, simulations were performed to understand the effects of the size and number of nanoparticles, and the sensing width between electrodes on the detection of biosignals. Then, a series of experiment was performed to validate the simulation results and understand the feasibility of the proposed microchip design. Both simulation and experimental results showed that as the sensing width between electrodes increased the conductivity decreased. Also, the conductivity increased as the density of gold nanoparticles increased. In addition, it was found that the conductivity that changes with the nanoparticles density could be approximated by a cumulative normal distribution function. The developed microchip system could effectively apply when a biosignals should be measured with a high sensitivity.

• KSBB Journal
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• v.25 no.2
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• pp.199-204
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• 2010

We generated the feasibility of DNA separation in free-solution using genetically engineered repetitive polypeptides as drag-tags. Two different-sized repetitive polypeptides were designed, expressed in E. coli, and purified. They were conjugated to a fluorescently labeled DNA (100 base), and the electrophoretic mobilities of these conjugate molecules were analyzed on a microchip. The results of these studies indicate that genetically engineered repetitive polypeptide is a prominent candidate for rapid and high-throughput genetic mutation detection, such as SNP analysis.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.3
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• pp.295-305
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• 2018

We present a passively Q-switched monolithic Er:Yb:glass microchip laser developed in our lab. The microchip laser can produce pulses at 1535 nm of the 'eye-safe' wavelengths with the pulse energy of 50 uJ and the pulse width of 4-6 ns. Using the laser we also designed and developed a pulsed Er:Yb:glass microchip laser rangefinder. Expressions for background and signal power, noise, and signal-to-noise ratio are reviewed. A computer simulation was used to optimize laser power, receiver aperture, and preamplifier bandwidth for the efficient system design of the laser rangefinder. Experimental results are presented to compare with the theory.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.45-50
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• 2014

A fully packed capillary electrochromatographic (CEC) microchip with an on-column micro-solid phase extraction (SPE) bed for the preconcentration and separation of organic analytes was prepared. A linear microchannel with monodisperse colloidal silica packing was formed on a cyclic olefinic copolymer microchip with two reservoirs on both ends. Silver-cemented silica packing frit structure was formed at the entrance of the microchannel by electroless plating treatment as a base layer. A gold coating was formed on it by reducing $Au^{3+}$ to gold with hydroxylamine. Finally micro-SPE bed was formed by self-assembly adsorption of 1-dodecanethiol on it. Micro-SPE beds were about 100-150 ${\mu}m$ long. Approximately $10^3$ fold sensitivity enhancements for Sulforhodamine B, and Fluorescein in nM concentration levels were possible with 80 s preconcentration. Basic extraction characteristics were studied.