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홍종간(Jonggan Hong),김동식(Dongsik Kim),최재명(Jaemyung Choi),황일두(Ildoo Hwang) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
Various types of microfabricated thermal cyclers have recently been developed for micro-PCR using MEMS technology. Most of these micro-PCR thermal cyclers consist of micro-chambers and micro-channels, together with a complicated microfluidic system for pumping, injecting and ejecting samples into the reaction chamber. In addition, conventional micro PCR thermal cyclers have thin-film-resistor heaters which induce unnecessary heat transfer to the chamber wall. In this work, a novel design of a micro-PCR system without the complex microfluidic system and unnecessary heat transfer is presented. The method is based on laser indirect heating of a small-volume sample with simultaneous monitoring and control of the temperature. The results demonstrate that the proposed microscale thermal technique can be employed to eliminate the cumbersome sample-handling process used in the conventional micro PCR process and to achieve effective heat transfer to a tiny amount of DNA sample.
홍종간(Jonggan Hong),최선락(Sun Rock Choi),김동식(Dongsik Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
This work reports development of novel liquid-level sensors based on the 3ω method. The sensors determine the liquid level by measuring the thermal response as in the conventional hot-wire technique. However the sensors employ an AC heating method to enhance the sensitivity, noise resistance and time response. Also, the microfabricated thin-film structure of the sensor provides mass-producibility as well as improved sensor performance owing to the increase in the surface-volume ratio of the sensor. Two different types of the sensor are developed: one for point detection of the fluid phase and the other for monitoring continuous variation of liquid level. Notable is that the performance of the sensor is not considerably affected by the liquid flow.
마이크로 채널 내 액체 시료의 실시간 열분석 기법 개발
최선락(Sun Rock Choi),홍종간(Jonggan Hong),김동식(Dongsik Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
This work introduces a novel method for real-time measurement of the thermal conductivity and heat capacity of nanoliter-scale liquid samples. The device uses a micromachined thermal sensor composed of a microchannel and a thin-film probe. The method, based on the 3w technique, employs a multiparameter-fitting scheme to determine the thermal properties with numerical computation of heat transfer. The results demonstrate that the sensor can measure the thermal conductivity and heat capacity of 12 nl samples simultaneously. Furthermore, real-time thermal characterization of fluid samples flowing in a microchannel has been demonstrated, manifesting strong potential of the proposed technique as an in-situ probe in various microfluidic applications.
입자크기와 레이저 조사가 나노유체의 열전도율 향상에 미치는 영향
김상현(Sang Hyun Kim),최선락(Sun Rock Choi),홍종간(Jonggan Hong),김동식(Dongsik Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
In this study, the effects of particle size and laser irradiation on thermal-conductivity of nanofluids are investigated experimentally. The thermal conductivity of nanofluids is measured by the transient hot-wire method using an anodized tantalum wire and the results are compared with theoretical models. Three different metallic oxide particles, alumina (Al₂O₃), zinc oxide (ZnO) and titanium dioxide (TiO₂) with three different mean diameters, are dispersed in distilled water and ethylene glycol to form nanofluids. Enhancement of the thermal conductivity of nanofluids is analyzed for ZnO nanofluids by varying the incident laser energy.