• 대한기계학회논문집B
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• 제30권2호
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• pp.110-116
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• 2006

A syringe pump or a device using high electric voltage has been used for controlling flows inside a LOC (lab-on-a-chip). Compared to LOC, however, these microfluidic devices are large and heavy that they are burdensome for a portable ${\mu}-TAS$ (micro total analysis system). In this study, a new flow control technique employing pressure regulators and pressure chambers was developed. This technique utilizes compressed air to control the micro-scale flow inside a LOC, instead of a mechanical actuator or an electric power supply. The pressure regulator controls the output air pressure by adjusting the variable resistor attached. We checked the feasibility of this system by measuring the flow rate inside a capillary tube of $100{\mu}m$ diameter in the Re numbers ranged from 0.5 to 50. In addition, the performance of this flow control system was compared with that of a conventional syringe pump. The developed flow control system was found to show superior performance, compared with the syringe pump. It maintains automatically the: air pressure inside a pressure chamber whether the flow inside the capillary tube is on or off. Since the flow rate is nearly proportional to the resistance, we can control flow in multiple microchannels precisely. However, the syringe pump shows large variation of flow rate when the fluid flow is blocked in the microchannel.

• Korean Chemical Engineering Research
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• 제50권4호
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• pp.738-742
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• 2012

본 연구에서는 알루미나 나노 템플레이트(anodic alumina oxide; AAO)를 이용하여 신속하면서도 효과적으로 나노입자 및 바이오물질을 분리, 농축할 수 있는 나노필터 소자를 개발하였다. 본 연구에서 사용한 나노필터 소자는 유체의 주입 및 흐름이 가능한 미세유체채널(microfluidic channel)을 PDMS에 패터닝하였다. 위아래로 형성된 PDMS 미세유체채널 사이로, 다양한 크기의 나노 다공을 형성하고 있는 AAO 막을 삽입하여 크기에 따른 나노입자 및 바이오 물질을 분리할 수 있었다. 위아래로 PDMS 유체채널과 AAO 분리막을 집적하고, 최종적으로 아크릴레이트 플락스틱(acrylic plastic)으로 전체 소자를 고정하여 나노필터유체소자를 제작하였다. 완성된 나노필터소자를 이용하여 나노입자의 농축효율 및 은나노입자가 뭉쳐져있는 필터존(filtration zone)으로부터 뎅기 바이러스(dengue virus)를 표면증강라만(surface enhanced Raman scattering)분석법에 의해 검출할 수 있었다.

• 대한기계학회논문집B
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• 제37권12호
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• pp.1159-1165
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• 2013

파우더 블라스팅은 미세 유리가공법으로서 가공속도가 빠르고 저비용의 장점이 있지만 유리를 취성파괴 시키기 때문에 표면거칠기가 좋지않다. 블라스팅된 표면에 저압의 워터젯을 분사하여 표면에서의 연마 슬러리의 흐름을 통해 표면거칠기를 저감할 수 있다. 본 연구에서는 소다라임 유리에 블라스팅으로 마이크로 채널을 가공한 후 워터젯을 연속 적용하고, 마이크로 채널의 표면거칠기 및 단면 형상의 변화의 과정을 관찰하였다. 워터젯의 적용결과, 초기단계에서는 블라스팅에 의한 미세 요철이 제거되었고, 이후 표면하부의 크랙이 제거되어 평균 표면거칠기 50 nm 근방의 매끈한 표면을 얻을 수 있었다. 표면거칠기 저감에 동반하여 채널단면의 확장 과정도 함께 관측하였다. 마지막으로 제안한 방법에 의해 미세유체칩의 가공 결과를 제시하였다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제8권4호
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• pp.233-239
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• 2003

For the quantitative analysis of an unknown sample a calibration curve should be obtained, as analytical instruments give relative, rather than absolute measurements. Therefore, researchers should make standard samples with various known concentrations, measure each standard and the unknown sample, and then determine the concentration of the unknown by comparing the measured value to those of the standards. These procedures are tedious and time-consuming. Therefore, we developed a polymer based microfluidic device from polydimethylsiloxane, which integrates serial dilution and capillary electrophoresis functions in a single device. The integrated microchip can provide a one-step analytical tool, and thus replace the complex experimental procedures. Two plastic syringes, one containing a buffer solution and the other a standard solution, were connected to two inlet holes on a microchip, and pushed by a hydrodynamic force. The standard sample is serially diluted to various concentrations through the microfluidic networks. The diluted samples are sequentially introduced through microchannels by electro-osmotic force, and their laser-induced fluorescence signals measured by capillary electrophoresis. We demonstrate the integrated microchip performance by measuring the fluorescence signals of fluorescein at various concentrations. The calibration curve obtained from the electropherograms showed the expected linearity.

• 한국가시화정보학회지
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• 제15권1호
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• pp.47-52
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• 2017

In droplet-based microfluidic systems, in-droplet preconcentration of a sample is one of the important prerequisites for biochemical or medical analysis. There have been a few studies on preconcentration in a moving droplet, but they are limited to practical applications since 1) their method are time-consuming or 2) they require specific properties such as electric and magnetic properties. In this study, we demonstrated the position control of polystyrene particles of 5 and $10{\mu}m$ in diameter inside a moving water-in-oil droplet using traveling surface acoustic waves. Since the frequencies for effective control of each diameter were found, microparticles with no labels could be utilized. In addition, the proposed method enabled on-demand preconcentration inside a polydimethylsiloxane microchannel. In-droplet preconcentration of microparticles was realized by splitting a mother droplet with manipulated particles at a downstream bifurcation zone. Given these advantages, the proposed system is a promising acoustofluidic lab-on-a-chip platform for preconcentration inside a droplet.

• 대한기계학회논문집A
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• 제34권12호
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• pp.1785-1791
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• 2010

중합효소 연쇄반응(PCR)을 수행하려면 세포 용해(cell lysis)와 DNA추출(DNA purification)과정이 포함된 시료 전처리 과정을 거쳐야 한다. 종래의 시료 전처리 과정은 계면활성제와 같은 세포용해 버퍼를 이용하거나 열 또는 전기적 방법으로 세포막 파열을 유도하여 세포벽을 깬 후에 잔여물 처리과정을 거쳐 DNA를 추출하게 된다. 본 연구에서는 마이크로 비드와 PDMS 기둥을 이용한 필터가 있는 시료 전처리용 바이오칩을 설계 및 제작하였다. 또한 제작된 바이오칩을 사용하여 $80^{\circ}C$에서 2분간 세포용해를 수행하고 DNA를 추출하였다. 칩에서 전처리과정을 거친 시료내의 DNA농도와 순도를 측정하고 DNA PCR과 겔 전기영동을 통해 시료 전처리용 바이오칩의 성능을 평가하였다.

• Tribology and Lubricants
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• 제39권5호
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• pp.197-202
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• 2023

Recently, research on experimental and analytical techniques utilizing microfluidic devices has been pursued. For example, lab-on-a-chip devices that integrate micro-devices onto a single chip for processing small sample quantities have gained significant attention. However, during sample preparation, unnecessary gases can be introduced into the internal channels, thus, impeding device flow and compromising specific function efficiency, including that of analysis and separation. Several methods have been proposed to mitigate this issue, however, many involve cumbersome procedures or suffer from complexities owing to intricate structures. Recently, some approaches have been introduced that utilize hydrophobic device structures to remove gases within channels. In such cases, the permeability of gases passing through the structure becomes a crucial performance factor. In this study, a method involving the deposition and sintering of diluted Ag-ink onto a silicon wafer surface is presented. This is followed by unstructured nano-pattern creation using a Metal Assisted Chemical Etching (MACE) process, which yields a nanostructured surface with unstructured pillar shapes. Subsequently, gas permeability in the spaces formed by these surface structures is investigated. This is achieved by experiments conducted to incorporate a pressure chamber and measure gas permeability. Trends are subsequently analyzed by comparing the results with existing theories. Finally, it can be confirmed that the significance of this study primarily lies in its capability to effectively evaluate gas permeability through unstructured pillar-like nanostructures, thus, providing quantitative values for the appropriate driving pressure and expected gas removal time in practical device operation.

• 대한기계학회논문집A
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• 제28권1호
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• pp.63-69
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• 2004

It is of great interest to enhance mixing performance in a microchannel in which the flow is usually characterized as a low Reynolds number (Re) so that good mixing is quite difficult to be achieved in this laminar flow regime. In this regard, we present a new chaotic passive micromixer, named Barrier Embedded Micromixer (BEM), of which the mixing mechanism is based on chaotic flows. In BEM, chaotic flow is induced by periodic perturbation of the velocity field due to periodically inserted barriers along the channel wall while a helical type of flow is obtained by slanted grooves on the bottom surface of the channel in the pressure driven flow. To experimentally compare the mixing performance, a T-microchannel and a microchannel with only slanted grooves were also fabricated. All microchannels were made of PDMS (Polydimethylsiloxane) from SU-8 masters that were fabricated by conventional photolithography. Mixing performance was experimentally characterized with respect to an average mixing intensity by means of color change of phenolphthalein as pH indicator. It was found that mixing efficiency decreases as Re increases for all three micromixers. Experimental results obviously indicate that BEM has better mixing performance than the other two. Chaotic mixing mechanism, suggested in this study, can be easily applied to integrated microfluidic systems , such as Micro-Total-Analysis-System, Lab-on-a-chip and so on.

• Journal of Microbiology and Biotechnology
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• 제17권1호
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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.

• 한국정밀공학회지
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• 제28권6호
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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.