• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.6
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• pp.599-606
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• 2010

In the present study, actuators with diaphragms of different thickness and chambers of different diameter are fabricated to examine experimentally how the behavior characteristics of the actuator diaphragm in a thermopneumatic micropump are affected by diaphragm thickness and chamber diameter under various operating conditions with different values of input voltage and frequency. The actuator comprises a microheater set on Pyrex glass, a chamber, and a diaphragm. For all values of the input energy, as the frequency decreases below 10 Hz, the maximum center deflection of the diaphragm greatly increases irrespective of diaphragm thickness and chamber diameter. At low frequencies, as the heat energy supplied to the chamber increases, the center of deflection of the diaphragm increases; the magnitude of deflection is high for thin diaphragms and for diaphragms whose chambers have small diameters. At frequencies higher than 10 Hz, all the design variables such as diaphragm thickness, chamber diameter, and the input energy have negligible effect on the center deflection of the diaphragm.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1196-1200
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• 2004

Micropump is very useful component in micro/nano fluidics and bioMEMS applications. In this study, a bubble-powered micropump was fabricated and tested. The micropump consists of two-parallel micro line heaters, a pair of nozzle-diffuser flow controller and a 1 mm in diameter, 400 ${\mu}m$ in depth pumping chamber. The two-parallel micro line heaters with 20 ${\mu}m-width$ and 200 ${\mu}m-length$ were fabricated to be embedded in the silicon dioxide layer of a wafer which serves as a base plate for the micropump. The pumping chamber, the pair of nozzle-diffuser unit and microchannels including the liquid inlet and outlet port were fabricated by etching through another silicon wafer. A glass wafer (thickness of $525{\pm}15$ ${\mu}m$) having two holes of inlet and outlet ports of liquid serve as upper plate of the pump. Finally the silicon wafer of the base plate, the silicon wafer of pumping chamber and the glass wafer were aligned and bonded (Si-Si bonding and anodic bonding). A sequential photograph of bubble nucleation, growth and collapse was visualized by CCD camera. Clearly liquid flow through the nozzle during the period of bubble growth and slight back flow of liquid at the end of collapsing period can be seen. The mass flow rate was found to be dependent on the duty ratio and the operation frequency. As duty ratio increases, flow rate decreases gradually when the duty ratio exceeds 60%. Also as the operation frequency increases, the flow rate of the micropump decreases slightly.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2251-2253
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• 2000

MEMS기술을 이용하여 단층 실리콘 나이트라이드($Si_{3}N_4$) 다이아프램을 제조하고, 이 다이아프램상에 저항성 가열 진공증착법과 고주파 마그네트론 스퍼터링법을 이용하여 차례로 In막과 ZnO막을 증착하고, In의 도핑을 위해 열처리하여 $NH_3$ 가스 감지용 마이크로센서를 제작하였다. 감지막의 열처리온도에 따른 구조적 및 전기적 특성은 XRD, SEM, AFM, 4-point probe 및 Electrometer를 통하여 각각 조사하였다. 제작된 센서의 열처리온도와 인가전력에 따라 $NH_3$ 가스에 대한 감도, 선택성 및 시간응답 특성을 조사하였다. 감지막 두께 3000 ${\AA}$, 열처리온도 400$^{\circ}C$로 제조된 마이크로 센서가 히터 인가전력 366 mW에서 100 ppm의 $NH_3$ 가스농도에서 대하여 16 %, 350 ppm의 가스농도에서 대하여 23 %의 가장 우수한 감도를 나타내었다. 그러나 CO 가스 및 $NO_x$ 가스에 대한 감지특성은 관찰되지 않았다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.7
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• pp.1071-1075
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• 2003

In this paper, we present a DNA manipulation device in the reaction chamber, which consists of a center electrode and circular outer electrodes of a reaction unit. The charged bio-molecules, DNA, are manipulated by the charge of the electrode in reaction unit. Controlling the induced dynamic electric field between the center electrode and the outer electrodes, concentration / repulsion / manipulation of bio-molecules are enabled at a periphery of electrode. Concentration of the fluorescent DNA at the center electrode is observed by applying ＋2V. Subsequently, applying －2V, the concentrated DNA is repelled rapidly from the center electrode, which makes dispersion completely in 0.5second. Furthermore, repeated applying ＋1V/－1V every 5 seconds at each outer electrode, we can circulate the DNA. We also investigate a micro-heater and sensor for DNA manipulation and reaction temperature. The coefficient of heat-resistance and heater temperature characteristic is 0.0043 and 100$^{\circ}C$/sec, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.113-113
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• 2009

This paper describes the characteristics of a poly 3C-SiC micro heater which was fabricated on $AlN(0.1{\mu}m)/3C-SiC(1.0{\mu}m)$ suspended membranes by surface micro- machining technology. The 3C-SiC and AlN thin films which have wide energy bandgap and very low lattice mismatch were used sensors for high temperature and voltage environments. The 3C-SiC thin film was used as micro heaters and temperature sensor materials simultaneously. The implemented 3C-SiC RTD (resistance of temperature detector) and the power consumption of micro heaters were measured and calculated. The TCR (thermal coefficient of the resistance) of 3C-SiC RTD is about -5200 $ppm/^{\circ}C$ within a temperature range from $25^{\circ}C$ to $50^{\circ}C$ and -1040 $ppm/^{\circ}C$ at $500^{\circ}C$. The micro heater generates the heat about $500^{\circ}C$ at 10.3 mW. Moreover, durability of 3C-SiC micro heaters in high voltages is better than pt micro heaters. A thermal distribution measured and simulated by IR thermovision and COMSOL is uniform on the membrane surface.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.7 s.250
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• pp.646-655
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• 2006

The present research is an experimental study on characteristics of cooling behavior for the adjacent copper blocks with surface roughness or micro-porous coated surface. The experiments were carried out at saturation state or within subcooled states of PF5060. The effects of heater orientation and the intervals between heating surfaces or substrates were investigated under various heat flux conditions. The boiling performance of copper block with micro-porous coated surface was better than that of copper block with surface roughness. It is understood that the bubble sweeping enhances boiling performance for the heaters with inclinations of $\theta=45^{\circ}\;and\;\theta=90^{\circ}$, where as the bubble flattening decreases boiling performance for the heaters with inclinations of $\theta=135^{\circ}\;and\;\theta=180^{\circ}$. In comparison to upper heater and below heater with orientation, the upper heater has lower superheat temperature than the below heater due to the bubble sweeping. It is also found that boiling performance decreases in the case of adjacent double heaters with only 0.2cm substrate interval.

• Journal of Sensor Science and Technology
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• v.17 no.3
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• pp.178-182
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• 2008

Planar type micro catalytic combustible gas sensor was developed by using nano crystalline $SnO_2$ Pt thin film as micro heater was deposited by thermal evaporation method on the alumina substrate. The thickness of the Pt heater was around 160 nm. The sensor showed high reliability with prominent selectivity against various gases(Co, $C_3H_8,\;CH_4$) at low operating temperature($156^{\circ}C$). The sensor with nano crystalline $SnO_2$ showed higher sensitivity than that without nano crystalline $SnO_2$. This can be explained by more active adsorption and oxidation of hydrogen by nano crystalline $SnO_2$ particles. The present planar-type catalytic combustible hydrogen sensor with nano crystalline $SnO_2$ is a good candidate for detection of hydrogen leaks.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.252-252
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• 2008

The microhotplates consisting of a Pt-ased heating element on AlN/poly 3C-SiC layers were fabricated. The microhotplate has a $600{\mu}m{\times}600{\mu}m$ square shaped membrane which made of $1{\mu}m$ thick ploycrystalline 3C-SiC suspended by four legs. 3C-SiC is known for excellent chemical durability, mechanical strength and sustaining of high temperature. The membrane is fabricated by surface micromachining using oxidized Si sacrificial layer. The Pt thin film is used for heating material and resist temperature sensor. The fabrication methodology allows intergration of an array of heating material and resist temperature detector. For reasons of a short response time and a high sensitivity a uniform temperature profile is desired. The dissipation of microhotplate was examined by a IR thermoviewer and the power consumption was measured. Measured and simulated results are compared and analyzed. Thermal characterization of the microhotplates shows that significant reduction in power consumption was achieved using suspended structure.

• Journal of Sensor Science and Technology
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• v.18 no.4
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• pp.311-315
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• 2009

This paper describes the characteristics of a poly 3C-SiC micro heater which was fabricated on AlN(0.1 $\mu$m)/3C-SiC(1.0 $\mu$m) suspended membranes by surface micro-machining technology. The 3C-SiC and AlN thin films which have wide energy band gap and very low lattice mismatch were used sensors for high temperature and voltage environments. The 3C-SiC thin film was used as micro heaters and temperature sensor materials simultaneously. The implemented 3CSiC RTD(resistance of temperature detector) and the power consumption of micro heaters were measured and calculated. The TCR(thermal coefficient of the resistance) of 3C-SiC RTD is about -5200 ppm/$^{\circ}C$ within a temperature range from 25 $^{\circ}C$ to 50 $^{\circ}C$ and -1040 ppm/$^{\circ}C$ at 500 $^{\circ}C$. The micro heater generates the heat about 500 $^{\circ}C$ at 10.3 mW. Moreover, durability of 3C-SiC micro heaters in high voltages is better than Pt micro heaters. A thermal distribution measured and simulated by IR thermovision and COMSOL is uniform on the membrane surface.

• Journal of Sensor Science and Technology
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• v.19 no.3
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• pp.197-201
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• 2010

This paper describes the fabrication and characteristics of a NO sensor using ZnO thin film integrated 3C-SiC micro heater based on polycrystalline 3C-SiC thin film of operation in harsh environments. The sensitivity, response time, and operating properties in high temperature and voltages of NO sensors based SiC MEMS are measured and analyzed. The sensitivity of device with pure ZnO thin film at the heater operating power of 13.5 mW ($300^{\circ}C$) is 0.875 in NO gas concentration of 0.046 ppm. In the case of Pt doping, the sensitivity of at power consumption of 5.9 mW ($250^{\circ}C$) was 1.92 at same gas flow rate. The ZnO with doped Pt was showed higher sensitivity, lower working temperature and faster adsorption characteristics to NO gas than pure ZnO thin film. The NO gas sensor integrated SiC micro heater is more strength than others in high voltage and temperature environments.