• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제53권4호
• /
• pp.231-236
• /
• 2004

A normally open thermopneumaticc-actuated microvalve has been fabricated and their properties are investigated. The advantages of the proposed microvalve are of the low cost fabrication process and the transparent optical property using polydimethylsiloxane (PDMS) and indium tin oxide (ITO) glass. The fabricated microvalves with in-channel configuration are easily integrated with other microfluidic devices on the same substrate. The fabrication process of thermopneumatic-actuated microvalvesusing PDMS is very simple and its performance is very suitable for a disposable lab-on-a-chip. The PDMS membrane deflection increases and the flow rates of the microchannel with microvalvels decrease as the applied power to the ITO heater increases. The powers at flow-off are dependent on the membrane thickness and the applied inlet pressure but are independent of the channel width of microvalves. The flow rate is well controlled by the switching function of ITO heater and the closing/opening times are around 20 sec and 25 sec, respectively.

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

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제53권6호
• /
• pp.342-346
• /
• 2004

A thermopneumatic-actuated polydimethylsiloxane (PDMS) micropump has been fabricated and their properties are characterized. The diffusers are used as a flow-rectifying element instead of passive check valves. The advantages of the proposed microvalve are of the low cost fabrication process and the transparent optical property using PDMS and indium tin oxide (ITO) glass. We presented the PDMS micropump that is easily integrated with the in-channel PDMS microvalves on the same substrate. The flowrate of the micropump increases linearly as the applied pulse voltage to the ITO heater increases. The fabricated ITO heater resistance is 6.54k$\Omega$. The peak of the flow rate is observed at the duty ratio of 10% for the applied pulse voltage of 55V at 6Hz and the maximum flow rate of 78nl/min is measured.

• Korean Chemical Engineering Research
• /
• 제59권1호
• /
• pp.100-105
• /
• 2021

본 연구는 적은 비용으로 분석 장치 없이 질병 진단 및 경과를 모니터링할 수 있는 종이-기반 분석 장치(paper-based analytical device, PAD)를 제작하기 위해 polydimethylsiloxane (PDMS) 블레이드 코팅 방법을 제안하였다. PAD 디자인은 레이저 커팅 기술로 쉽게 몰드에 적용할 수 있으며, 제작된 몰드로 블레이드 코팅을 수행하여 완전한 소수성 장벽 형성에 필요한 조건을 확립하였다. 코팅 조건인 잉크의 두께와 종이와의 접촉시간에 따라 PDMS 소수성 장벽의 구조와 친수성 채널의 크기 변화를 분석하여 안정적으로 소수성 장벽을 형성할 수 있는 조건을 최적화하였다. 최적화된 방법을 바탕으로 PAD를 제작하여 특별한 분석기기 없이 단백질, 당, 메탈이온을 검출하여 바이오센서에 응용가능함을 증명하였다.

• Korean Chemical Engineering Research
• /
• 제58권1호
• /
• pp.122-126
• /
• 2020

본 연구에서는 폴리디메틸실록산(PDMS)과 모세관-미세몰딩(MIMIC) 기술을 활용하여 마이크로패턴 채널 시스템을 제작하고, 단일 세포 수준에서 극성화 패턴으로 형성되는 분자 신호를 고해상도 세포 이미징을 통해 분석하였다. 이 과정에서 혈소판유래성장인자(PDGF)가 처리된 세포에서는 세포 이동에 중요한 세 종류의 신호인 포스포이노시티드 3-인산화효소(PI3K), Rac 및 액틴(Actin) 신호가 선두(front)영역에서 후미(rear)영역에 비해 강하게 활성화 하는 데 반해, 마이오신 경쇄(MLC) 신호는 비특이적 경향성을 보여주었다. 본 연구 결과는 향후 마이크로패턴의 미세환경에서 세포 극성화 신호와 세포 이동과의 상관 관계를 연구하는 데 중요한 도움이 될 것으로 사료된다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
• /
• pp.274.2-274.2
• /
• 2013

We described a simple and efficient fabrication method for generating microfluidic channels with a circular-cross sectional geometry by exploiting the reflow phenomenon of a thick positive photoresist. Initial rectangular shaped positive photoresist micropatterns on a silicon wafer, which were fabricated by a conventional photolithography process, were converted into a half-circular shape by tuning the temperature to around $105^{\circ}C$. Through optimization of the reflow conditions, we could obtain a perfect circular micropattern of the positive photoresist, and control the diameter in a range from 100 to 400 ${\mu}m$. The resultant convex half-circular photoresist was used as a template for fabricating a concave polydimethylsiloxane (PDMS) through a replica molding process, and a circular PDMS microchannel was produced by bonding two half-circular PDMS layers. A variety of channel dimensions and patterns can be easily prepared, including straight, S-curve, X-, Y-, and T-shapes to mimic an in vivo vascular network. To inform an endothelial cell layer, we cultured primary human umbilical vein endothelial cells (HUVECs) inside circular PDMS microchannels, and demonstrated successful cell adhesion, proliferation, and alignment along the channel.

• 대한기계학회논문집B
• /
• 제33권5호
• /
• pp.311-317
• /
• 2009

Due to extremely small device size and velocity scale, mixing in microchannel take place very slowly by way of molecular diffusion transport. Mixing enhancement becomes a central issue in microfluidics for biomedical and chemical applications. In this work, The optimization results and validation through experiment and fabrication. In this efficient micromixer design, it is essential to evaluate mixing efficiency with good precision. Mixing efficiency for Y-channel micromixer is measured by fluorescence intensity using LIF(Laser Induced Fluorescence) Confocal Microscope. The Y-channel micromixers are fabricated with polydimethylsiloxane(PDMS). Nile Blue A is injected into the micromixer as a fluorescence dye for measuring of fluorescence intensity by He/Ne laser. Throughout the experiments and computer simulation, accurate mixing efficiency evaluation process for a PDMS Y-channel micromixer is established.

• 한국정밀공학회지
• /
• 제27권2호
• /
• pp.29-33
• /
• 2010

We have investigated fs-laser ablation as well as optoperforation threshold of PDMS (Polydimethylsiloxane) thin lid cover on ${\mu}$-channel with changing the flow medium from water to hemoglobin. The ablation threshold is found to be independent of both PDMS thin film thickness and flow medium, but the optoperforation threshold is dependent on the films thickness. The observation that the ablation process is well described with simple two-temperature model supposed that the cover lid PDMS of $\mu$-channel be processed with minimized thermal effects by fs-laser with low laser fluence.

• 한국전자파학회논문지
• /
• 제27권2호
• /
• pp.123-130
• /
• 2016

본 논문에서는 원격 화학 센서로 활용 가능한 플렉서블 미세유체 메타물질 흡수체를 제안한다. 제안된 흡수체는 잉크젯 프린팅 기법으로 종위 기판 위에 인쇄한 분할고리공진기(SRCR: Split Ring Cross Resonator)와 Polydimethylsiloxane(PDMS) 기판에 레이저 식각된 미세유체 채널로 구성되어 있어 매우 유연한 특징을 보인다. 본 연구에서 제안한 메타물질 흡수체는 미세유체 채널에 주입된 화학물질에 따른 실효 유전율의 변화를 공진주파수의 이동으로 감지할 수 있다. 제안된 흡수체는 시뮬레이션과 측정을 통하여 성능을 검증하였다. 측정 결과, 공기의 경우에는 10.49 GHz에서 흡수가 되었고, 에탄올과 탈이온수의 경우에는 각각 10.04 GHz와 8.9 GHz에서 흡수체로 동작함을 확인할 수 있었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제54권5호
• /
• pp.227-231
• /
• 2005

We have developed a microsystem with a capillary electrophoresis (CE) and an electrochemical detector (ECD). The microfabricated CE-ECD systems are adequate for a disposable type and the characteristics are optimized for an application to the electrochemical detection. The system was realized with polydimethylsiloxane (PDMS)-glass chip and indium tin oxide electrode. The injection and separation channels (80 um wide$\ast$40 um deep) were produced by moulding a PDMS against a microfabricated master with relatively simple and inexpensive methods. A CE-ECD systems were fabricated on the same substrate with the same fabrication procedure. The surface of PDMS layer and ITO-coated glass layer was treated with UV-Ozone to improve bonding strength and to enhance the effect of electroosmotic flow. For comparing the performance of the ITO electrodes with the gold electrodes, gold electrode microchip was fabricated with the same dimension. The running buffer was prepared by 10 mM 2-(N-morpholino)ethanesulfonic acid (MES) titrated to PH 6.5 using 0.1 N NaOH. We measured olectropherograms for the testing analytes consisted of catechol and dopamine with the different concentrations of 1 mM and 0.1 mM, respectively. The measured current peaks of dopamine and catechol are proportional to their concentrations. For comparing the performance of the ITO electrodes with the gold electrodes, electropherograms was measured for CE-ECD device with gold electrodes under the same conditions. Except for the base current level, the performances including sensitivity, stability, and resolution of CE-ECD microchip with ITO electrode are almost the same compared with gold electrode CE-ECD device. The disposable CE/ECD system showed similar results with the previously reported expensive system in the limit of detection and peak skew. When we are using disposable microchips, it is possible to avoid polishing electrode and reconditioning.