• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권7호
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• pp.328-334
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• 2002

The DNA chips are devices associating the specific recognition properties of two DNA single strands through hybridization process with the performances of the microtechnology. In the literature, the "Gene chip" or "DNA chip" terminology is employed in a wide way and includes macroarrays and microarrays. Standard definitions are not yet clearly exposed. Generally, the difference between macro and microarray concerns the number of active areas and their size, Macroarrays correspond to devices containing some tens spots of 500$\mu$m or larger in diameter. microarrays concern devices containing thousnads spots of size less than 500$\mu$m. The key technical parameters for evaluating microarray-manufacturing technologies include microarray density and design, biochemical composition and versatility, repreducibility, throughput, quality, cost and ease of prototyping. Here we report, a new method in which minute particles are arranged in a random fashion on a chip pattern using random fluidic self-assembly (RFSA) method by hydrophobic interaction. We intend to improve the stability of the particles at the time of arrangement by establishing a wall on the chip pattern, besides distinction of an individual particle is enabled by giving a tag structure. This study demonstrates the fabrication of a chip pattern, immobilization of DNA to the particles and arrangement of the minute particle groups on the chip pattern by hydrophobic interaction.ophobic interaction.

• 대한기계학회논문집B
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• 제38권3호
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• pp.263-270
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• 2014

유체이송 기술은 최근 마이크로 유체시스템 개발에서 핵심문제로 인식되고 있다. 본 논문에서는 외부동력을 사용하지 않고 액적을 이송시킬 수 있는 새로운 개념을 제안하고, 수치해석을 통해 증명하였다. 제안된 장치는 표면을 단순하게 친수성과 소수성 표면의 복합표면으로 구성하는 것이다. 새로운 개념을 입증하기 위한 수치해석은 보존적인 압력기반 유한체적방법에 기초한 비정렬 셀 중심 방법 및 VOF 방법에 체적포착법인 CICSAM을 채용하고 있는 자체개발 코드(PowerCFD)를 사용하였다. 연구결과 본 연구에서 제안된 개념이 마이크로 유체시스템에서 액적이송에 대해 우수한 성능을 나타내는 것으로 확인되었다.

• 한국가시화정보학회지
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• 제18권3호
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• pp.116-121
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• 2020

In this study, a single-phase analysis of droplet slug with different contact angles was performed based on the visualization of experimental results. Droplet slug - flowing between gases in a hydrophobic mini channel - moves with a triple contact line without a gas liquid film on the wall. The results show that the rotational flow inside the droplet occurred; this was compared and verified with the results of two-phase analysis. The pressure field shows pressure rise at the front and rear ends. The effective length - the section that satisfies the laminar flow condition - became shorter as the droplet velocity increased. The Choi's correlation for the effective length agrees with this analysis results with a slight difference. This difference is judged as the difference in the contact angle of the slug model.

• 대한수의학회지
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• 제25권2호
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• pp.149-153
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• 1985

Salmonella pullorum strain W was serially passaged on the brain heart infusion agar containing acrdine orange(AO) as a concentration of 100 mcg/ml. S. pullorum AO60 and S. pullorum AO150, which were subcultured 60 and 150 passages on AO media, were examined for permeability barrier function of the cell wall. AO60 and AO150 were appeared to be decreased in susceptibility against hydrophobic substances such as crystal violet, chloramphenicol and rifamycin, which might be resulted from the changes of permeability barrier function of the cell wall. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis of bacterial protein, the protein profiles of AO6O and AO150 didn't differ significantly from W, but increased amount of the band of MW 140,000-145,000 was confirmed. And [G+C] contents of DNA in AO60 and A0150 were decreased than that of W.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2007년도 추계학술대회
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• pp.84-87
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• 2007

Recently, many studies concern on the slip flow and slip length, which allow liquid flow to reduce drag force in microchannel. However, until now not enough investigation is performed experimentally to understand the slip flow in the superhydrophobic microchannel exhibiting riblet structures on vertical wall. Here we investigated and compared the slip flows according to the surface characteristics; hydrophilic, hydrophobic, and superhydrophobic wettabilities. Using the micro-PIV, velocity profiles can be obtained in the glass (hydrophilic), PDMS (hydrophobic), and micro-structured PDMS (superhydrophobic) microchannels. For both PDMS and superhydrophobic PDMS microchannels, we observed the slip effects showing the microscale slip lengths. Due to the micro-riblet, there are two distinctive flow characteristics on the riblet surface and the liquid meniscus in the valleys.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.656-657
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• 2008

The droplet dynamics in a hydrophilic/hydrophobic microchannel, which is applicable to a typical proton exchange membrane fuel cell (PEMFC), is studied numerically by solving the equations governing conservation of mass and momentum. The liquid-gas interface or droplet shape is determined by a level set method which is modified to treat contact angles. The matching conditions at the interface are accurately imposed by incorporating the ghost fluid approach based on a sharp-interface representation. The effects of contact angle, inlet flow velocity, droplet size and side wall on the droplet motion are investigated parametrically. Based on the numerical results, the droplet dynamics including the sliding and detachment of droplets is found to depend significantly on the contact angle. Also, a droplet removal process is demonstrated on the combination of hydrophilic and hydrophobic surfaces.

• 멤브레인
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• 제24권3호
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• pp.240-248
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• 2014

열유도상분리법(TIPS) 및 연신의 복합공정을 적용하여 막증류(Membrane distillation, MD)용 다공성 PVDF 중공사 분리막을 제조하였다. 분리막의 투과도를 증가시키기 위하여 분리막 투과도를 향상시킬 수 있는 성능인자들 중 분리막의 벽두께를 감소시키고자 하였다. 분리막의 두께를 감소시키기 위하여 분리막 제조 시 토출량을 감소시키고 중공 형성 시 주입하는 bore fluid 주입량을 증대시켰다. 토출량의 감소 및 bore fluid의 증가에 따라 벽두께는 감소하였고, 공기투과도와 수투과도는 크게 증가하였으며, 결과적으로 막증류 공정에 적용 시 투과플럭스도 증가하는 경향을 보여 주었다.

• 대한화장품학회지
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• 제32권1호
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• pp.29-33
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• 2006

본 연구는 효소의 활성을 저해하는 주위 환경, 특히 열로부터 효소의 활성을 장기간 유지할 수 있는 효소 안정화 시스템에 대한 것으로, 이 시스템은 poly(${\epsilon}-caprolactone$) (PCL) 마이크로 캡슐로, 파파인 효소를 모델 효소로 하여, poly(propylene glycol) (PPG) 층이 코어 효소층을 둘러싸고 있는 형태로 설계되어 있다. 공촛점 현미경 및 장기 열 안정도 결과를 분석해본 결과, 파파인 효소가 소수성 PPG로 둘러쌓여 있고, 배타적 볼륨 효과(exclusive volume effect)에 의해 안정화되어 있음을 밝힐 수 있었다. 이와 같이 향상된 효소의 열 안정도는 소수성 사슬이 긴 PPG를 사용할수록 증가됨을 알 수 있었으며, 이것은 효소와 PPG 계면 사이에서 PPG 층이 파파인 효소를 효과적인 형태 고정(conformational anchoring)을 통해 안정화한 것임을 알 수 있었다.

• Journal of Mechanical Science and Technology
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• 제20권5호
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• pp.710-716
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• 2006

Micro-PIV system with a high speed CCD camera is used to measure the flow field near the advancing meniscus of a water slug in microchannels. Image shifting technique combined with meniscus detecting technique is proposed to measure the relative velocity of the liquid near the meniscus in a moving reference frame. The proposed method is applied to an advancing front of a slug in microchannels with rectangular cross section. In the case of hydrophilic channel, strong flow from the center to the side wall along the meniscus occurs, while in the case of the hydrophobic channel, the fluid flows in the opposite direction. Further, the velocity near the side wall is higher than the center region velocity, exhibiting the characteristics of a strong shear-driven flow. This phenomenon is explained to be due to the existence of small gaps between the slug and the channel wall at each capillary corner so that the gas flows through the gaps inducing high shear on the slug surface. Simulation of the shape of a static droplet inside a cubic cell obtained by using the Surface Evolver program is supportive of the existence of the gap at the rectangular capillary corners. The flow fields in the circular capillary, in which no such gap exists, are also measured. The results show that a similar flow pattern to that of the hydrophilic rectangular capillary (i.e., center-to-wall flow) is always exhibited regardless of the wettability of the channel wall, which is also indicative of the validity of the above-mentioned assertion.

• Korea-Australia Rheology Journal
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• 제17권4호
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• pp.207-215
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• 2005

We present a finite difference solution for electrokinetic flow in rectangular microchannels encompassing Navier's fluid slip phenomena. The externally applied body force originated from between the nonlinear Poisson-Boltzmann field around the channel wall and the flow-induced electric field is employed in the equation of motion. The basic principle of net current conservation is applied in the ion transport. The effects of the slip length and the long-range repulsion upon the velocity profile are examined in conjunction with the friction factor. It is evident that the fluid slip counteracts the effect by the electric double layer and induces a larger flow rate. Particle streak imaging by fluorescent microscope and the data processing method developed ourselves are applied to straight channel designed to allow for flow visualization of dilute latex colloids underlying the condition of simple fluid. The reliability of the velocity profile determined by the flow imaging is justified by comparing with the finite difference solution. We recognized the behavior of fluid slip in velocity profiles at the hydrophobic surface of polydimethylsiloxane wall, from which the slip length was evaluated for different conditions.