• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.1999-2004
• /
• 2004

Experiments were conducted to investigate the flow characteristics of water through rectangular PDMS microchannels with a hydraulic diameter ranging from 66.67 to 200 ${\mu}m$. In the experiments, the flow rate and pressure drop across the microchannels were measured at steady states. The experimental results were compared with the predictions from the conventional laminar flow theory. A significant difference between the experimental data and the theoretical predictions was found. Experimental results indicate that the pressure gradient and flow friction in microchannels are higher than those from the conventional laminar flow theory. This may be attributed to the fact that there exists effect of surface roughness of the microchannels. In this study, a surface roughness model is implemented to interpret the experimental data. A good agreement between the experimental data and the numerical predictions with a surface roughness model were found.

• 청정기술
• /
• 제20권3호
• /
• pp.226-231
• /
• 2014

본 연구는 미세 몰드 기술을 이용하여 산세기 자극에 따라 모양이 변화하는 야누스 입자를 제조하는 방법에 관한 것이다. 야누스 입자는 산세기(pH) 응답형 단량체인 acrylic acid (AA)를 사용하여 친수성 부분을 제조하고, trimethylolpropane triacylate (TMPTA)를 사용하여 소수성 부분을 제조하였다. 제조된 야누스 입자는 산세기 변화에 따라서 친수성 부분의 팽윤이 유도되며 결과적으로 자극 응답성을 가짐을 증명 하였다. 자극 응답성 정도는 산세기의 범위 또는 AA의 조성을 다양화 함으로써 제어가 가능하다. 더 나아가 야누스 입자의 양쪽 부분이 반대 전하를 띄는 특성을 부여하기 위해 AA와 2-(dimethylamino)ethyl methacrylate (DAEMA)를 사용하여 양극성 야누스 입자를 제조하였다. 양극성 야누스 입자는 동일한 산세기 조건에서 서로 다른 팽윤율을 갖게 되며 비대칭적 형상을 띄게 된다. 결론적으로, 본 연구에서는 야누스 입자의 친수성 부분에 산세기 응답형 단량체를 사용함으로써, 산세기 자극에 의해 가역적으로 모양 변형이 가능한 야누스 입자를 제조하였다. 본 연구를 통해 제조된 자극 응답형 야누스 입자는 향후 바이오 센서나 검출 기구 등에 활용 될 것으로 기대한다.

• Smart Structures and Systems
• /
• 제12권1호
• /
• pp.1-22
• /
• 2013

Magnetic nanoparticle based bioseparation in microfluidics is a multiphysics phenomenon that involves interplay of various parameters. The ability to understand the dynamics of these parameters is a prerequisite for designing and developing more efficient magnetic cell/bio-particle separation systems. Therefore, in this work proof-of-concept experiments are combined with advanced numerical simulation to design and optimize the capturing process of magnetic nanoparticles responsible for efficient microfluidic bioseparation. A low cost generic microfluidic platform was developed using a novel micromolding method that can be done without a clean room techniques and at much lower cost and time. Parametric analysis using both experiments and theoretical predictions were performed. It was found that flow rate and magnetic field strength greatly influence the transport of magnetic nanoparticles in the microchannel and control the capturing efficiency. The results from mathematical model agree very well with experiments. The model further demonstrated that a 12% increase in capturing efficiency can be achieved by introducing of iron-grooved bar in the microfluidic setup that resulted in increase in magnetic field gradient. The numerical simulations were helpful in testing and optimizing key design parameters. Overall, this work demonstrated that a simple low cost experimental proof-of-concept setup can be synchronized with advanced numerical simulation not only to enhance the functional performance of magneto-fluidic capturing systems but also to efficiently design and develop microfluidic bioseparation systems for biomedical applications.

• 대한기계학회논문집A
• /
• 제26권9호
• /
• pp.1923-1930
• /
• 2002

In this paper, we present modeling and simulation of microlens formation by means of a deep X-ray lithography followed by a thermal treatment of a PMMA (Polymethylmethacrylate) sheet. According to this modeling, X-ray irradiation causes the decrease of molecular weight of PMMA, which in turn decreases the glass transition temperature and consequently causes a net volume increase during the thermal cycle resulting in a swollen microlens. In this modeling, the free volume theory including the relaxation process during the cooling process was considered. The simulation results indicate that the modeling in this study is able to predict the fabricated microlens shapes and the variation pattern of the maximum heights of microlens which depends on the conditions of the thermal treatment. The prediction model could be applied to optimization of microlens fabrication process and to designing a micro mold insert for micromolding processes.

• 한국분말재료학회지
• /
• 제9권4호
• /
• pp.267-272
• /
• 2002

The production of micro components is one of the leading technologies in the fields of information and communiation, medical and biotechnology, and micro sensor and micro actuator system. Microfabrication (micromachining) techniques such as X-ray lithography, electroforming, micromolding and excimer laser ablation are used for the production of micro components out of silicon, polymer and a limited number of pure metals or binary alloys. However, since the first development of microfabrication technologies there have been demands for the cost-effective replication in large scale series as well as the extended range of available material. One such promising process is micro powder injection molding (PIM), which inherits the advantages of the conventional PIM technology, such as low production cost, shape complexity, applicability to many materials, applicability to many materials, and good tolerance. This paper reports on a fundamental investigation of the application of W-Cu powder to micro metal injection molding (MIM), especially in view of achieving a good filling and a safe removal of a micro mold conducted in the experiment. It is absolutely legitimate and meaningful, at the present state of the technique, to continue developing the micro MIM towards production processes for micro components.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2009년도 제38회 동계학술대회 초록집
• /
• pp.84-84
• /
• 2010

In this study, we report on the novel lithographic patterning method to fabricate organic-semiconductor devices based on photo and e-beam lithography with well-known silicon technology. The method is applied to fabricate pentacene-based organic field effect transistors. Owing to their solubility, sub-micron sized patterning of P3HT and PEDOT has been well established via micromolding in capillaries (MIMIC) and inkjet printing techniques. Since the thermally deposited pentacene cannot be dissolved in solvents, other approach was done to fabricate pentacene FETs with a very short channel length (~30nm), or in-plane orientation of pentacene molecules by using nanometer-scale periodic groove patterns as an alignment layer for high-performance pentacene devices. Here, we introduce the atomic layer deposition of $Al_2O_3$ film on pentacene as a passivation layer. $Al_2O_3$ passivation layer on OTFTs has some advantages in preventing the penetration of water and oxygen and obtaining the long-term stability of electrical properties. AZ5214 and ma N-2402 were used as a photo and e-beam resist, respectively. A few micrometer sized lithography patterns were transferred by wet and dry etching processes. Finally, we fabricated sub-micron sized pentacene FETs and measured their electrical characteristics.

• 한국진공학회지
• /
• 제20권1호
• /
• pp.63-69
• /
• 2011

본 연구에서는 기존 실리콘 반도체 기술 기반의 포토 및 이빔 리소그래피 공정을 통하여 유기 반도체 소자를 패터닝하였다. P3HT나 PEDOT 등의 유기 반도체는 용매에 녹기 때문에 MIMIC (micro-molding in capillaries)이나 inkjet printing 기술을 이용하여 마이크로미터 크기의 소자 제작이 가능하였으나, 펜타신은 용매에 녹지 않기 때문에 매우 복잡한 방법으로 마이크로미터 크기의 소자를 제작하여왔다. 그러나, 본 연구에서는 원자층 증착 방법으로 증착한 산화 알루미늄막을 펜타신의 보호층으로 이용하여 기존의 포토 및 이빔 리소그래피 방법으로 마이크로미터크기의 펜타신 소자를 제작하였으며 그 전기 특성을 확인하였다.

• 대한기계학회논문집A
• /
• 제34권7호
• /
• pp.859-866
• /
• 2010

본 연구에서는 다단 마이크로 구조물의 대량성형을 위하여, 모듈화된 초소형몰드 시스템(MSMS)을 이용한 초소형 사출성형 공정을 수행하였다. 본 연구에서 적용된 초소형몰드 시스템은 여러 모듈들로 구성되어 있으며, 각 모듈들은 다양한 단면 마이크로 구조물을 가지고 있다. 초소형몰드 시스템의 모듈들은 X-선 리소그래피 공정 및 니켈 전주도금 공정으로 제작되었으며, 다양한 모듈들을 조합 및 결합함으로써 복잡한 형상을 가지는 초소형몰드 시스템을 효과적으로 구현할 수 있다. 이와 같은 초소형몰드 시스템을 적용함으로써, 본 연구에서는 다단 구조물의 표면에 마이크로 삼각 프리즘이 주기적으로 배열되어 있는 다단 마이크로 구조물의 초소형 사출성형 공정을 성공적으로 수행하였다.

• 전기학회논문지
• /
• 제58권1호
• /
• pp.147-154
• /
• 2009

This paper presents a grating~integrated SPR (Surface Plasmon Resonance) sensor chip for simple and inexpensive biomolecule detection. The grating-integrated SPR sensor chip has two sensing channels having a nano grating for SPR coupling. An external mirror is used for multi channel SPR sensing. The present sensor chip replaces bulky and expensive optical components, such as fiber-optic switches or special shaped prisms, resulting in a simple and inexpensive wavelength modulated multi-channel SPR sensing system. We fabricate a SPR sensor chip integrated with 835 nm-pitch gratings by a micromolding technique to reduce the fabrication cost. In the experimental characterization, the refractive index sensitivity of each sensing channel is measured as $321.8{\pm}8.1nm$/RI and $514.3{\pm}8.lnm$/RI, respectively. 0.5uM of the target biomolecule (streptavidin) was detected by a $1.13{\pm}0.16nm$ shift of the SPR dip in the 10%-biotinylated sample channel, while the SPR dip in the reference channel for environmental perturbation monitoring remained at the same position. From the experimental results, multi-channel biomolecule detection capability of the present grating-integrated SPR sensor chip has been verified. On the basis of the preliminary experiments, we successfully measured the binding reaction rate for the $2\;nM{\sim}200\;nM$ monoclonal-antibiotin, thus verifying biomolecule concentration detectability of the present SPR sensor chip. The binding reaction rates measured from the present SPR sensor chip agredd well with those from a commercialized SPR sensor.

• 폴리머
• /
• 제38권3호
• /
• pp.391-396
• /
• 2014

고분자 마이크로니들은 몰딩 공정으로 쉽고 저렴하게 생산할 수 있지만 3차원 고분자 마이크로 구조체에 수용액 기반의 약물 코팅은 어려움이 있다. 2차원 형태의 평면 금속 마이크로니들에 약물을 코팅한 기존의 코팅 마이크로니들과 비교하여 볼 때 3차원 구조의 고분자 마이크로니들은 코팅 면적이 2배 넓고 단위면적당 마이크로니들의 수를 크게 증가시킴으로써 두 배 이상의 약물을 경피를 통해 전달할 수 있다. 증점제와 계면활성제 첨가 방법의 경우 2차원의 평면에는 균일한 코팅을 얻을 수 있었지만 3차원 구조의 고분자 마이크로니들 표면에서는 만족할 코팅을 얻지 못했다. 하지만, 고분자 마이크로니들 표면을 금속 코팅 혹은 UV/ozone으로 처리한 경우 3차원의 마이크로 니들 표면에 만족할 코팅을 얻을 수 있었으나 금속 코팅의 경우 피부에 찌르고 제거하는 과정에서 금속이 피부 안에 남는 안전성 문제가 있어 UV/ozone을 최종 표면 처리 방법으로 선정하였다. 이렇게 처리한 고분자 마이크로니들 표면에 calcein이 첨가된 코팅물질로 코팅된 마이크로니들은 15분 이상의 피부 투여로 코팅물질을 성공적으로 진피층까지 전달할 수 있었다.