• Journal of information and communication convergence engineering
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• v.6 no.1
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• pp.38-42
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• 2008

Highly sensitive and mechanically stable gas sensors have been fabricated using the microfabrication and micromachining techniques. The sensing materials used to detect the offensive $CH_3SH$ and $(CH_3)_3N$ gases are 1 wt% Pd-doped $SnO_2$ and 6 wt% $Al_2O_3$-doped ZnO, respectively. The optimum operating temperatures of the devices are $250^{\circ}C$ and $350^{\circ}C$ for $CH_3SH$ and $(CH_3)_3N$, respectively and the corresponding heater power is, respectively, about 55mW and 85mW. Excellent thermal insulation is achieved by the use of a double-layer membrane: i.e. $0.2{\mu}m$-thick silicon nitride and $1.4{\mu}m$-thick phosphosilicate glass. The sensors are mechanically stable enough to endure the heat cycles between room temperature and $350^{\circ}C$, at least for 30 days.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.146-150
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• 1996

A thermal micro actualtor has been fabricated using surface micromachining techniques. It consists of doped ploysilicon as a moving part and TEOS(Tetra Ethyl Ortho Silicate) as a sacrificial layer. The polysilicon was annealed for the reduction of residual stress which is the main cause to its deformation such as bending and buckling. And the newly developed HF VPE(vapor phase etching)process was also used as an effective release method for the elimination of sacrificaial layer. With noliquid involved during any of the steps for relasing, unlike other reported relase techniques, the HF VPE pocess has produced polysilicon microstructures with virtually no process-induced stiction problem. The actuation is incured by the thermal expasion due to current flow in active polysilicon cantilever, which motion is amplified bylever mechanism. The thickness of pllysilicon is 2 .mu. m and the length of active and passive polysilicon cantilever are 500 .mu. m, respectively. The moving distance of polysilicon actuator was experimentally conformed as large as 21 .mu. m at the input voltage level of 10 V and 50Hz square wave. These micro actuator technology can be utilized for the fabrication of MEMS (microlectromechanical system) such as microrelay, which requires large displacement or contact force but relatively slow response.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.424-433
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• 2001

We present a new electrostatic repulsive-force microactuator using a lateral repulsive force induced by an asymmetric distribution of electrostatic field. The lateral repulsive force has been characterized by a simple analytical equation, derived from a finite element simulation. A set of repulsive force polysilicon microactuators has been designed and fabricated by a 4-mask surface-micromachining process. Static and dynamic micromechanical behavior of the fabricated microactuators has been measured at the atmospheric pressure for a varying bias voltage. The static displacement of the fabricated microactuator, proportional to the square of the DC bias voltage, is obtained as 1.27 $\mu\textrm{m}$ for the DC bias voltage of 140V. The resonant frequency of the repulsive-force microactuator increases from 11.7 kHz to 12.7 kHz when the DC bias voltage increases from 60V to 140V. The measured quality-factor varies from 12 to 13 for the bias volatge range of 60V∼140V. The characteristics of the electrostatic repulsive-force have been discussed and compared and compared with those of the conventional electrostatic attractive-force.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.4
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• pp.43-45
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• 2001

For photosensitive and micro-structuring in $Li_2O-A1_2O_3-SiO_2$glasses by laser treatment, Nd:YAG laser in 355 nm and 1064 nm wavelength was irradiated to the glass to investigate fracture characterization and optical changes. The fractured glass surfaces irradiated by 1064 nm laser was observed by Scanning Electron Microscope(SEM) and optical microscope, and optical changes caused by 355 nm later was identified from absorption spectra. In this study, it could be expected that the laser treatment technology will be utilized for 3-dimensional micro-structure, internal waveguide, optical memory by optical absorption changes in glass matrix.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.612-614
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• 1997

Silicon based micro mirror array is a highly efficient component for use in optical applications such as adaptive optical systems and optical correlators. A micro mirror array designed, fabricated and tested here is consisted of $5{\times}5$ single layer polysilicon, electrostatically driven actuators. In this paper, deflection characteristics and pull-in behavior of the actuators for analog control was studied and particularly, the influence of the residual stress in flexure beams for the restorative force of actuators was considered. The springs are modeled as a residual stress-free spring and a spring with residual stress. In calculation, a mirror with the residual stress-free springs has 30.3N/m spring constant and 31.1V pull-in voltage. On the other hand, a mirror with the stressed springs has 23.6N/m and 27.4V respectively. The experimental result, which is 20.5N/m and 25.5V, shows that the stressed springs ore well modeled.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.12
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• pp.1639-1645
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• 2002

Micro engine that includes Micro scale combustor is fabricated. Design target was focused on the observation of combustion driven actuation in MEMS scale. Combustor design parameters are somewhat less than the size recommended by feasibility test. The engine structure is fabricated by isotropic etching of the photosensitive glass wafers. Electrode formed by electroplating of the Nickel. Photosensitive glass can be etched isotropically with almost vertical angle. Bonding and assembly of structured photosensitive glass wafer form the engine. Combustor size was determined to be 1 mm scale. Movable piston is engraved inside the wafer. Ignition was done by nickel spark plug which was electroplated with thickness of 40 ${\mu}{\textrm}{m}$. The wafers were bonded by epoxy that resists high temperature. In firing test due to the bonding method and design tolerance pressure buildup by reaction was not confirmed. But ignition, flame propagation and actuation of micro structure from the reaction was observed. From the result basement of design and fabrication technology was obtained.

• Journal of information and communication convergence engineering
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• v.14 no.4
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• pp.246-251
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• 2016

In this study, we developed a reduced 94 GHz hybrid ring coupler on a GaAs substrate in order to demonstrate the possibility of the integration of various passive components and MMICs in the millimeter-wave range. To reduce the size of the hybrid ring coupler, we used multiple open stubs on the inside of the ring structure. The chip size of the reduced hybrid ring coupler with multiple open stubs was decreased by 62% compared with the area of the hybrid ring coupler without open stubs. Performance in terms of the loss, isolation, and phase difference characteristics exhibited no significant change after the use of the multiple open stubs on the inside of the ring structure. The reduced hybrid ring coupler showed excellent coupling loss of $3.87{\pm}0.33dB$ and transmission loss of $3.77{\pm}0.72dB$ in the measured frequency range of 90-100 GHz. The isolation and reflection were -48 dB and -32 dB at 94 GHz, respectively. The phase differences between two output ports were $180^{\circ}{\pm}1^{\circ}$ at 94 GHz.

• Journal of Sensor Science and Technology
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• v.12 no.4
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• pp.156-163
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• 2003

Polypyrrole microactuators have been fabricated by the standard surface micromachining method combined with the electropolymerization of polypyrrole. The fundamental structure to verify the feasibility of the fabrication process is polypyrrole cantilever. Based on these process, polypyrrole grippers and valves for the manipulation of the cell have been fabricated. Grippers have the structure of bone and muscle which are rigid polymers and polypyrrole, respectively. Valves have the assembled structure of channels with polypyrrole cantilevers. The proposed fabrication process and structures are expected to be used for bio-related applications, for example, the cell manipulation.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.5
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• pp.182-188
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• 2003

We have demonstrated a fluidic technique for self-assembly of microfabricated parts onto substrate using patterned shapes of magnetic force self-assembled monolayers (SAMs). The metal particles and the array were fabricated using the micromachining technique. The metal particles were in a multilayer structure (Au, Ti, and Ni). Sidewalls of patterned Ni dots on the array were covered by thick negative photoresist (SU-8), and the array was magnetized. The array and the particles were mixed in buffer solution, and were arranged by magnetic force interaction. Binding direction of the metal particle onto Ni dots was controlled by multilayer structure and direction of magnetization. A quarter of total Ni dots were covered by the particles. The binding direction of the particles was controllable, and condition of particles was almost even with the Au surface on top. The particles were successfully arranged on the array.

• Journal of Electrical Engineering and information Science
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• v.2 no.4
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• pp.66-71
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• 1997

The dielectrophoretic(DEP) force acting on a cell in an electric field is experimentally determined. A cell is accelerated by the DEP force in an electric field generated between micro planar electrodes. the position of the cell is measured and the velocity and acceleration of the cell are calculated based on the measured position data. The DE force is determined from the motion equation of a moving cell in suspension. The electrode structure is fabricated by micromachining technology and the height of electrodes is 1 $\mu\textrm{m}$. Radish cell and yeast are used in th experiments. In the case of radish cell, the DEP force increases as voltage or frequency(1MHz∼3MHz) increases. The voltage dependence can be explained that the DEP force increases when ▽│E│$^2$increases. The frequency dependence means that Re[x\ulcorner] of radish cell is maximized in a certain frequency. In the case of yeast, the DEP force increases only as voltage increases. The reason for the voltage dependence is the same with the case of radish. The DEP force increases only as voltage increases. The reason for the voltage dependence is the same with the case of radish. The DEP force on a yeast does not vary when the frequency varies from 1MHz to 3MHz. This result coincides with the fact that the value of calculated Re[x\ulcorner] is constant in the test frequency range.