• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1645-1646
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• 2006

Micro ElectroMechanical Systems (MEMS) 기술을 이용한 초미세 유체 제어 시스템 (마이크로 펌프, 마이크로 밸브, 마이크로 채널, 마이크로 믹서 등)은 화학, 생명분야의 DNA 분석, 항원-항체 분석, 질병의 진단 등에 사용되는 lab-on-a-chip, micro total analysis system ($\mu$-TAS) 등에서 화학 및 바이오 유체를 제어하는 분석 시스템의 일부분으로서 사용되며 필수적으로 요구된다. 본 논문에서는 이러한 microchip을 구현하기 위해 초미세 유체 제어 소자인 마이크로 펌프와 밸브를 같은 기관 위에 polydimethylsiloxane (PDMS)와 indium tin oxide (ITO)-Glass를 사용하여 동일한 구조로 집적 하였다. 마이크로 펌프의 pumping rate은 인가 직류 펄스 전력의 주파수와 duty 비를 변화시켜 최적화하였다. 직류 펄스 전력 500 mW를 인가하였을 때 주파수 2 Hz, duty 비 7 %에서 약 $1.05{\mu}l/min$의 최대 유량이 측정되었다. 마이크로 밸브는 ITO 히터에 전력을 인가함으로서 유량의 on/off 제어가 잘 됨을 확인할 수 있었고 유체를 closing하기 위해 필요한 전력은 약 300 mW이다.

• Journal of Sensor Science and Technology
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• v.31 no.3
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• pp.175-179
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• 2022

The physical properties of biomaterials are important for their isolation and separation from body fluids. In particular, the precise evaluation of the multi-physical properties of single biomolecules is essential in that the correlation between physical and biological properties of specific biomolecule. However, the majority of scientific equipment, can only determine specific-physical properties of single nanoparticles, making the evaluation of the multi-physical properties difficult. The improvement of analytical techniques for the evaluation of multi-physical properties is therefore required in various research fields. In this study, we developed a motion-tracking algorithm to evaluate the multi-physical properties of single-nanoparticles by analyzing their behavior. We observed the Brownian motion and electric-field-induced drift of fluorescent nanoparticles injected in a microfluidic chip with two electrodes using confocal microscopy. The proposed algorithm is able to determine the size of the nanoparticles by i) removing the background noise from images, ii) tracking the motion of nanoparticles using the circular-Hough transform, iii) extracting the mean squared displacement (MSD) of the tracked nanoparticles, and iv) applying the MSD to the Stokes-Einstein equation. We compared the evaluated size of the nanoparticles with the size measured by SEM. We also determined the zeta-potential and surface-charge density of the nanoparticles using the extracted electrophoretic velocity and the Helmholtz-Smoluchowski equation. The proposed motion-tracking algorithm could be employed in various fields related to biomaterial analysis, such as exosome analysis.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.273-273
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• 2013

Recently, Point-of-care (POC) testing microdevices enable to do the patient monitoring, drug screening, pathogen detection in the outside of hospital. Immunochromatographic strip (ICS) is one of the diagnostic technologies which are widely applied to POC detection. Relatively low cost, simplicity to use, easy interpretations of the diagnostic results and high stability under any circumstances are representative advantages of POC diagnosis. It would provide colorimetric results more conveniently, if the genetic analysis microsystem incorporates the ICS as a detector part. In this work, we develop a reverse transcriptase-polymerase chain reaction (RT-PCR) microfluidic device integrated with a ROSGENE strip for colorimetric influenza H1N1 virus detection. The integrated RT-PCR- ROSGENE device is consist of four functional units which are a pneumatic micropump for sample loading, 2 ${\mu}L$ volume RT-PCR chamber for target gene amplification, a resistance temperature detector (RTD) electrode for temperature control, and a ROSGENE strip for target gene detection. The device was fabricated by combining four layers: First wafer is for RTD microfabrication, the second wafer is for PCR chamber at the bottom and micropump channel on the top, the third is the monolithic PDMS, and the fourth is the manifold for micropump operation. The RT-PCR was performed with subtype specific forward and reverse primers which were labeled with Texas-red, serving as a fluorescent hapten. A biotin-dUTP was used to insert biotin moieties in the PCR amplicons, during the RT-PCR. The RT-PCR amplicons were loaded in the sample application area, and they were conjugated with Au NP-labeled hapten-antibody. The test band embedded with streptavidins captures the biotin labeled amplicons and we can see violet colorimetric signals if the target gene was amplified with the control line. The off-chip RT-PCR amplicons of the influenza H1N1 virus were analyzed with a ROSGENE strip in comparison with an agarose gel electrophoresis. The intensities of test line was proportional to the template quantity and the detection sensitivity of the strip was better than that of the agarose gel. The test band of the ROSGENE strip could be observed with only 10 copies of a RNA template by the naked eyes. For the on-chip RT-PCR-ROSGENE experiments, a RT-PCR cocktail was injected into the chamber from the inlet reservoir to the waste outlet by the micro-pump actuation. After filling without bubbles inside the chamber, a RT-PCR thermal cycling was executed for 2 hours with all the microvalves closed to isolate the PCR chamber. After thermal cycling, the RT-PCR product was delivered to the attached ROSGENE strip through the outlet reservoir. After dropping 40 ${\mu}L$ of an eluant buffer at the end of the strip, the violet test line was detected as a H1N1 virus indicator, while the negative experiment only revealed a control line and while the positive experiment a control and a test line was appeared.

• Journal of Life Science
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• v.34 no.5
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• pp.339-355
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• 2024

The pulmonary system is a highly complex system that can only be understood by integrating its functional and structural aspects. Hence, in vivo animal models are generally used for pathological studies of pulmonary diseases and the evaluation of inhalation toxicity. However, to reduce the number of animals used in experimentation and with the consideration of animal welfare, alternative methods have been extensively developed. Notably, the Organization for Economic Co-operation and Development (OECD) and the United States Environmental Protection Agency (USEPA) have agreed to prohibit animal testing after 2030. Therefore, the latest advances in biotechnology are revolutionizing the approach to developing in vitro inhalation models. For example, lung organ-on-a-chip (OoC) and organoid models have been intensively studied alongside advancements in three-dimensional (3D) bioprinting and microfluidic systems. These modeling systems can more precisely imitate the complex biological environment compared to traditional in vivo animal experiments. This review paper addresses multiple aspects of the recent in vitro modeling systems of lung OoC and organoids. It includes discussions on the use of endothelial cells, epithelial cells, and fibroblasts composed of lung alveoli generated from pluripotent stem cells or cancer cells. Moreover, it covers lung air-liquid interface (ALI) systems, transwell membrane materials, and in silico models using artificial intelligence (AI) for the establishment and evaluation of in vitro pulmonary systems.

• Journal of the Korean Chemical Society
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• v.48 no.5
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• pp.483-490
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• 2004

We have developed a novel polymerase chain reaction (PCR)-microchip gel electrophoresis (MGE) method based on the sieving gel mixture of commercially available poly(vinylpyrrolidone) (PVP) and hydroxy ethyl cellulose (HEC) for the rapid detection and diagnosis of the orf virus (ORFV) from Korean indigenous goat. After amplification of 594-bp DNA fragment from the B2L gene of ORF virus, the amplicon was analyzed by the MGE separation. The glass microfluidic chip (64 mm total length (36 mm effective length)${\times}$90 ${\mu}$m width${\times}$20 ${\mu}$m depth) allowed the fast detection and diagnosis of ORFV in the mixture of 1.0% PVP ($M_r$ 360,000) and 1.0% HEC ($M_r$250,000) as a sieving matrix with better resolution and reproducibility of DNA fragments. Under the electric field of 277.8 V/cm, the 594-bp DNA was analyzed within 4 min. Compared to traditional slab gel electrophoresis, the PCR-MGE method was twenty times faster and an effective clinical method for the quantitative analysis of ORFV.