• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.647-648
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• 2011

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권10호
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• pp.532-535
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• 2001

The sputtering condition of Cr thin film was established in order to get Cr gate electrode having a vertical wall structure for Mo-tip FEA. In case of Mo-tip FEA which had a vertically-etched Cr gate electrode, the field enhancement factor, was relatively increased and so the field emission performance in terms of turn-on voltage, emission current and trans-conductance could be improved when compared with the devices having a tapered gate wall.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1950-1953
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• 1996

A $1\;{\times}\;4$ micro mirror array is designed and fabricated. In contrast to other micro mirrors which utilize torsional flexure hinges or cantilevers for restoring torque and supporting purpose, we have placed a substrate hinge structure under each mirror. Each micro mirror consists of address electrode, substrate hinge consisting of pin and staple, supporter post, and mirror plate. Electrical connection between mirror plate and ground electrode is established by substrate hinge. Mirror undergoes a rotational motion due to electrostatic force when voltage difference is applied between address electrode and mirror plate. Micro mirrors with two different types of staple shape and two different pin sizes are designed and fabricated. Each mirror is designed to have ${\pm}\;10^{\circ}$ of deflection angle and have $100\;{\times}\;110\;{\mu}m^2$ of size.

• Journal of Electrical Engineering and Technology
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• 제6권3호
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• pp.402-407
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• 2011

The current paper describes a simpler ground-type, single-plate electrowetting configuration for droplet transport in digital microfluidics without performance degradation. The simplified fabrication process is achieved with two photolithography steps. The first step simultaneously patterns both a control electrode array and a reference electrode on a substrate. The second step patterns a dielectric layer at the top to expose the reference electrode for grounding the liquid droplet. In the experiment, a $5{\mu}m$ thick photo-imageable polyimide, with a 3.3 dielectric constant, is used as the dielectric layer. A 10 nm Teflon-AF is coated to obtain a hydrophobic surface with a high water advancing angle of $116^{\circ}$ and a small contact angle hysteresis of $5^{\circ}$. The droplet movement of 1 mM methylene blue on this simplified device is successfully demonstrated at control voltages above the required 45 V to overcome the contact angle hysteresis.

• Journal of Semiconductor Engineering
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• 제1권3호
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• pp.88-98
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• 2020

As biosensors are widely used in the medical field, flexible devices compatible with live animals have aroused great interest. Especially, significant research has been carried out to develop implantable or skin-attachable devices for real-time bio-signal sensing. From the device point of view, various biosensor types such as field-effect transistors (FETs) and multi-electrode arrays (MEAs) have been reported as diverse sensing strategies. In particular, the flexible FETs and MEAs allow semiconductor engineering to expand its application, which had been impossible with stiff devices and materials. This review summarizes the state-of-the-art research on flexible FET and MEA biosensors focusing on their materials, structures, sensing targets, and methods.

• 센서학회지
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• 제10권4호
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• pp.259-265
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• 2001

FET형 용존산소 센서는 pH-ISFET를 기본 소자로하여 pH 감지 게이트 근처에 백금으로 된 작업 전극을 형성한 구조를 가지고 있다. 작업전극에 특정한 전위를 인가하면 전기분해로 인하여 용존산소의 농도에 비례하는 수소 이온이 pH 감지 게이트 주변에 발생된다. 따라서 pH-ISFET를 통하여 수소 이온 농도의 변화량을 검출하면 용존산소의 농도를 측정할 수 있게된다. 본 논문에서는 이러한 FET형 용존산소 센서를 어레이 형태로 제작하여 적용하고 측정의 신뢰성을 높이기 위한 알고리즘을 도입한 FET형 용존산소 센서 어레이 측정 시스템을 개발하였다. 또한 상용 용존산소 측정기와 그 성능을 비교 분석하였다.

• 센서학회지
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• 제23권1호
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• pp.42-45
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• 2014

Recently, tremendous application utilizing electrospun nanofibers have been actively reported due to its several advantages, such as high surface to volume ratio, simple fabrication and high-throughput manufacturing. In this paper, we developed highly sensitive and consistent nanofiber humidity sensor by electrospinning. The humidity sensor was fabricated by rapid electrospinning (~2 sec) $TiO_2$/PVP/LiCl mixed solution on the micro-interdigitated electrode. In order to evaluate the humidity sensing performances, we measured current response using DC bias voltage under various relative humidity levels. The results show fast response / recovery time and marginal hysteresis as well as long-term stability. In addition, with the aid of micro-interdigitated electrode, we can reduce a total resistance of the sensor and increase the total reaction area of nanofibers across the electrodes resulting in high sensitivity and enhanced current level. Therefore, we expect that the electrospun nanofiber array for humidity sensor can be feasible and promising for diverse humidity sensing application.

• Smart Structures and Systems
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• 제28권6호
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• pp.737-744
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• 2021

In this study, structural health monitoring (SHM) methods of carbon fiber reinforced plastics (CFRPs) were investigated using electrical resistance. The developed sensing technique monitored electrical resistance in accordance with the impact damage of a CFRP. The changes in electrical resistances with multiple electrode sets enabled SHM without extra sensors so that this technique can be called self-sensing. Moreover, this study proposed electrodes only at peripheral side of a structure to minimize the number of electrodes compared to those in an array which has square number of sensors as the sensing area increases. For the intensive investigation, electromechanical sensitivity in terms of electrode distance was analyzed and optimized under drop weight impact testing. Then, SHM methods with electrodes in an array and electrodes in peripheral edges were comparatively investigated. The developed methods successfully localized impact damages into 2D coordinates. Furthermore, damage severity can be shown with a damage map by calculating electrical resistance change ratio. Therefore, structural health self-sensing system using electrical resistance was successfully developed with the minimum number of electrodes.

• 대한기계학회논문집B
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• 제36권3호
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• pp.241-249
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• 2012

본 논문에서는 유체흐름방향과 예각으로 놓여있는 평면 교차전극 위를 지나가는 입자의 크기에 따른 측면방향 변위에 대하여 소개한다. 아울러, 유체흐름방향과 평면 교차전극 사이의 각도에 따른 측면방향 변위의 변화를 보인다. 본 논문에서는 선전하(line charge) 모델을 이용하여 크기가 다른 세 종류의 형광 polystyrene(PS) 입자의 측면방향 변위를 이론적으로 예측하였다. 크기에 따른 입자의 측면방향 변위의 변화를 이용하여, 크기별로 입자를 연속적으로 분리할 수 있는 측면방향 유전영동 미세분리기를 개발하였다. 3, 5, 10 ${\mu}m$ PS 입자의 혼합물을 이용하여 분리한 실험결과로 부터 개발된 측면방향 유전영동 미세분리기는 3 ${\mu}m$ PS 입자를 99.86%, 5 ${\mu}m$를 98.82%, 10 ${\mu}m$를 99.69%의 높은 효율로 각각 분리할 수 있음을 확인하였다. 이로부터 제안된 측면방향 유전영동 미세분리기는 다종 혼합물로부터 다양한 크기의 입자들을 한 번에 분리하는 기술로 널리 활용될 수 있을 것으로 기대된다.

• Journal of Radiation Protection and Research
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• 제45권1호
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• pp.35-44
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• 2020

Background: Cadmium zinc telluride (CZT) is a promising material because of a high detection efficiency, good energy resolution, and operability at room temperature. However, the cost of CZT dramatically increases as its size increases. In this study, to achieve a large effective volume with relatively low cost, an array structure comprised of individual virtual Frisch-grid CZT detectors was proposed. Materials and Methods: The prototype consisted of 2 × 2 CZTs, a holder, anode and cathode printed circuit boards (PCBs), and an application-specific integrated circuit (ASIC). CZTs were used and the non-contacting shielding electrode method was applied for virtual Frisch-grid effect. An ASIC was used, and the holder and the PCBs were fabricated. In the current system, because the CZTs formed a common cathode, a total of 5 channels were assigned for data processing. Results and Discussion: An experiment using ¹³⁷Cs at room temperature was conducted for 10 minutes. Energy and timing information was acquired and the depth of interaction was calculated by the timing difference between the signals of both electrodes. Based on obtained three-dimensional position information, the energy correction was carried out, and as a result the energy spectra showed the improvements. In addition, a Compton image was reconstructed using the iterative method. Conclusion: The virtual Frisch-grid CZT detector based on the array structure was developed and the energy spectra and the Compton image were successfully acquired.