• Journal of Microbiology and Biotechnology
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• v.17 no.1
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• pp.5-14
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• 2007

Nanotechnology is the creation and utilization of materials, devices, and systems through the control of matter on the nanometer. The technology has been applied to biodevices such as bioelectronics and biochips to improve their performances. Nanoparticles, such as gold (Au) nanoparticles, are the most widely used of the various other nanotechnologies for manipulation at the nanoscale as well as nanobiosensors. The immobilization of biomolecules is playing an increasingly important role in the development of biodevices with high performance. Nanopatteming technology, which is able to increase the density of chip arrays, offers several advantages, including cost lowering, simultaneous multicomponent detection, and the efficiency increase of biochemical reactions. A microftuidic system incorporated with control of nanoliter of fluids is also one of the main applications of nanotechnologies. This can be widely utilized in the various fields because it can reduce detection time due to tiny amounts of fluids, increase signal-to-noise ratio by nanoparticles in channel, and detect multi-targets simultaneously in one chamber. This article reviews nanotechnologies such as the application of nanoparticles for the detection of biomolecules, the immobilization of biomolecules at nanoscale, nanopatterning technologies, and the microfluidic system for molecular diagnosis.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.6
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• pp.751-757
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• 2011

Subminiature devices such as Lab-on-a-chip and p-TAS(Micro Total Analysis System) have been intensively studied in biotechnology and chemistry, In many cases, a micromixer was widely used to mix different solutions for synthesizing novel materials. However, in microfluidic system, there is generally a laminar flow under very small Reynolds number so it is difficult to mix each solution perfectly. To settle this problem, we propose a new mixing mechanism which generates a horizontal and vertical multi-mixing (HVM) flow for effective mixing within a short mixing section. We evaluated the proposed mechanism using CFD analysis, and the results showed that the HVM mechanism had a relative high-effectiveness comparing to the existing methods.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1844-1852
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• 2001

Recent developments in microfluidic devices based on microelectromechanical systems (MEMS) technique find many practical applications, which include electronic chip cooling devices, power MEMS devices, micro sensors, and bio-medical devices among others. For the design of such micro devices, flows characteristics inside a microchannel have to be clarified which exhibit somewhat different characteristics compared to conventional flows in a macrochannel. In the present study microchannels of various hydraulic diameters are fabricated on a silicon wafer to study the pressure drop characteristics. The effect of abrupt contraction and expansion is also studied. It is found from the results that the friction factor in a straight microchannel is about 15% higher than that in a conventional macrochannel, and the loss coefficients in abrupt expansion and contraction are about 10% higher than that obtained through conventional flow analysis.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.6
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• pp.853-859
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• 2017

Terrorists always threats the global security with the possibility of using prohibited warfare, NBCs(Nuclear, Biological and Chemical Warfare). Compared to other prohibited warfares, most of biological warfare agents (BWAs) have no physical properties and time delays from spread to affect. Therefore the early detection is important to protect and decontaminate from BWAs. On the preliminary detection stage for suspicious material, most of detection kits only serve to know weather the BWAs exists or not. Due to this reason, simple field confirmation testing for suspicious substances have been used to identify materials which show negative result on detection kits. Considering the current Lab on a Chip(LOC) technologies, we suggest simple identification platform for unknown suspicious substances based on paper fluidics. We hope that our research will envision the future direction for the specific point-of-view for LOC technologies on detection strategy of BWAs.

• Current Optics and Photonics
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• v.8 no.1
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• pp.86-96
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• 2024

This research investigation employs a terahertz (THz) time-domain spectroscopy system to study the terahertz spectral characteristics of five different citrates in both solution and solid state. The citrates under examination are lithium citrate, monosodium citrate, disodium citrate, trisodium citrate, and potassium citrate. The results show that the THz absorption coefficients of the first four citrate solutions exhibit a decreasing trend with increasing concentration. However, the potassium citrate solution shows an opposite phenomenon. At the same time, the absorption coefficients of lithium citrate, trisodium citrate, and potassium citrate solutions are compared at the same concentration. The results indicate that the absorption coefficient of citrate solution increases in proportion to the increase of metal cation radius, which is explained from the perspective of the influence of metal cations on hydrogen bonds. In addition, we also study the absorption peaks of solid citrates, and characterize the formation mechanism of the absorption peaks by molecular dynamics simulations. This methodology can be further extended to the study of multitudinous salts, presenting theoretical foundations for the detection in food and medicine industries.

• JSTS:Journal of Semiconductor Technology and Science
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• v.1 no.4
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• pp.239-247
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• 2001

The Fluorescence-Activated Cell Sorter (FACS) is a well-established instrument used for identifying, enumerating, classifying and sorting cells by their physical and optical characteristics. For a miniaturized FACS device, a disposable plastic microchip has been developed which has a hydrodynamic focusing chamber using soft lithography. As the characteristics of the spatially confined sample stream have an effect on sample throughput, detection efficiency, and the accuracy of cell sorting, systematic fluid dynamic studies are required. Flow visualization is conducted with a laser scanning confocal microscopy (LSCM), and three-dimensional flow structure of the focused sample stream is reconstructed from 2D slices acquired at $1\mutextrm{m}$ intervals in depth. It was observed that the flow structure in the focusing chamber is skewed by unsymmetrical velocity profile arising from trapezoidal cross section of the microchannel. For a quantitative analysis of a microscopic flow structure, Confocal Micro-PIV system has been developed to evaluate the accelerated flow field in the focusing chamber. This study proposes a method which defines the depth of the measurement volume using a detection pinhole. The trajectories of red blood cells (RBCs) and their interactions with surrounding flow field in the squeezed sample stream are evaluated to find optimal shape of the focusing chamber and fluid manipulation scheme for stable cell transporting, efficient detection, and sorting

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.4
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• pp.309-314
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• 2005

We performed a basic experiment for the rapid, on-line, real-time measurement of hepatitis B surface antigen using a surface plasmon resonance biosensor. We immobilized anti­HBsAg (hepatitis B surface antigen) polyclonal antibody, as a ligand, to the dextran layer on a CM5 chip surface that had previously been activated by N-hydroxysuccinimide. A sample solution containing HBsAg was fed through a microfluidic channel, and the reflecting angle change due to the mass increase from the binding was detected. The binding characteristics between HBsAg and its polyclonal antibody followed the typical monolayer adsorption isotherm. When the entire immobilized antibody had interacted, no additional, non-specific binding occurred, suggesting the immunoreaction was very specific. The bound antigen per unit mass of the antibody was independent of the immobilized ligand density. No significant steric hindrance was observed at an immobilization density of approximately $17.6 ng/mm^2$. The relationship between the HBsAg concentration in the sample solution and the antigen bound to the ligand was linear up to ca. $40{\mu}g$/mL. This linearity was much higher than that of the ELISA method. It appeared the anti­gen-antibody binding increased as the immobilized ligand density increased. In summary, this study showed the potential of this SPR biosensor-based method as a rapid, simple and multi­sample on-line assay. Once properly validated, it may serve as a more efficient method for HBsAg quantification for replacing the ELISA.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.109-109
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• 2017

알지네이트 하이드로 젤은 해조류에서 추출되는 천연 고분자인 알지네이트가 칼슘 또는 마그네슘 양이온과 이온가교(Ioninc cross linking)를 형성할 때 알지네이트의 고분자 구조가 칼슘, 마그네슘 양이온을 감싸면서 형성되는 고분자이다. 알지네이트 하이드로 젤은 높은 생체적합성(Biocompatibility)으로 인해 세포 재생을 위한 조직공학 및 재생의학, 약물전달 등의 제약 관련 분야에 광범위하게 적용될 수 있는 물질로 많은 연구가 이루어지고 있다. 본 연구에서는 마이크로 플루이딕 칩을 이용하여 알지네이트 튜브를 제조하였다. 먼저 유동 포커싱 방식(flow focussing)을 유도할 수 있는 PDMS(Polydimethylsiloxane) 마이크로 플루이딕 칩을 제조하였다. 마이크로 플루이딕 칩은 CNC(Computer Numeric Control) milling machine을 이용한 template를 만들고 NOA mold를 이용하여 최종 PDMS 칩을 제작하였다. 튜브를 만들기 위한 마이크로 채널은 내부 채널 ($200{\times}200um$), 중간 채널 ($200{\times}200um$) 및 외부 채널 ($200{\times}200um$)로 구성되며 내부, 중간, 외부의 유체가 합류하는 수집채널은 폭 500 um, 깊이 200 um로 구성되었다. 운반체로는 5%의 acetic acid를 함유한 mineral oil를 이용하였으며 내부의 core flow는 $H_2O$로 하였다. 중간 유체인 2% 알지네이트 프리폴리머는 칼슘 이온의 존재 하에서 젤화 과정이 매우 빠르기 때문에 마이크로 채널 내부에서의 반응을 제어하고 막힘을 방지하기 위해 수용성 복합 칼슘-에틸렌 디아민 테트라 아세트산 (EDTA)을 사용하였다. 본 마이크로 플루이딕 칩에 각각의 유체를 이동시켰을 때, 운반체인 oil phase의 수소이온은 중간 유체인 알지네이트 프리폴리머와의 계면을 통해 확산되어 Ca-EDTA 복합체로부터 칼슘 양이온의 방출을 유발하게 된다. 방출된 칼슘 양이온은 알지네이트 고분자와의 이온 가교를 통해 알지네이트 하이드로 젤을 형성하여, 각 유체의 flow에 따라 알지네이트 튜브를 쉽고 빠르게 제조 가능하였다. 본 연구에서 제조된 알지네이트 튜브는 인체 내 장기간 약물 전달을 위한 나노섬유로 활용하거나 인공혈관을 구성하는 extracellular matrix로 활용될 잠재력을 가지고 있어 추후 활발한 연구개발이 진행될 예정이다.

• 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.