• Proceedings of the KSME Conference
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• 2005.11a
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• pp.44.2-44.2
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• 2005

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.63.1-63.1
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• 2005

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.411-412
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• 2008

The high performance 94 GHz MMIC(Monolithic Micro-wave Integrated Circuit) single balanced mixer was designed and fabricated, using MHEMT structure based diodes and a CPW(Coplanar Waveguide) tandem coupler. A novel single-balanced structure of diode mixer is proposed in this work, where a 3-dB tandem coupler with two section of parallel-coupled line. Implemented air-bridge crossover structures achieve wide frequency operation and the fabricated mixer exhibits excellent LO-RF isolation, larger than 30 dB, in the 5 GHz bandwidth of 91-96 GHz. A good conversion loss of 7.4 dB is measured at 94 GHz. The proposed MHEMT-based diode mixer shows superior LO-RF isolation and conversion loss to those of the W-band mixers reported to date.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2811-2816
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• 2007

We conducted a numerical study of AC-electroosmotic (alternating current) effect on the fluid flow and mixing in a 3-D microchannel. The microchannel used as an efficient micro-mixer is composed of a channel and a series of pairs of electrodes attached in zigzag pattern on the bottom wall. The AC electric field is applied to the electrodes so that a steady flow current takes place around the electrodes. This current is flowing across the channel and thus contributing to the mixing of the fluid within the channel. We performed numerical simulations by using a commercial code to obtain a steady flow field. This steady flow is then used in evaluation of the mixing performance via the concept of mixing index. It was found that good combination of two kinds of electrode, which gave us a good mixing, is not simple harmonic. And when the length ratio of these two kinds of electrode is 2:1, we can get the best mixing effect.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.27-30
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• 2005

In a microfluidic chips pressure driven flow or electro-osmotic flow has been usually employed to deliver bio-samples. Flow in the chips is usually slow and the mixing performance is poor. A micro-mixer with a rapid mixing is important for practical applications. In this study a newly designed and electro-osmotic driven micro-mixer is proposed. This design is comprised of a channel and a series of metal electrodes periodically attached on the side surface. In this configuration electro-osmotic flows and the stirring effects are simulated three-dimensionally using a commercial code, CFD-ACE. Focus is given the effect on the electro-osmotic flow characteristics under the local variation of the electric field.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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• pp.430-437
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• 2006

The mixing effect is studied by comparing rotating and oscillating stirrers in the micro channel. The cases of Re=10 to 80 with various stirring speeds are considered to analysis the effect of Re and stirrer speed for the mixing. Under Re=20, the oscillating stirrer represents better mixing rate than the rotating stirrer up to the critical stirrer speed which has a maximum efficiency. Over Re=30, the results of oscillating and rotating stirrer show that the faster the stirrer speed, the higher the mixing effect within the concerned stirrer speed range and the oscillating stirrer keeps the higher mixing rate. It was found that the mixing effect is a function which has an optimum of the Reynolds number and the stirrer speed. The D2Q9 Lattice Boltzmann Method is used due to the merits of calculation for the unsteady flow with moving boundary.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.12
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• pp.1549-1556
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• 2004

We have deigned, fabricated and compared four different types of static chaos microfluid mixers, including the mixers using straight channel flow, microblock-induced alternating whirl flow, microchannel-induced lamination flow, and combined alternating whirl-lamination flow. Among them, the alternating whirl-lamination (AWL-type) mixer, composed of 3-D rotationally arranged microblocks and dividing microchannels fabricated by conventional planar lithography process, is effective to reduce the mixing length over wide flow rate ranges. We characterize the performance of the fabricated mixers, through the flow visualization technique using phenolphthalein solution. We verify that the AWL-type microfluid mixer shows the shortest fluid mixing length of 2.8mm∼5.8mm for the flow rate range of Re=0.26∼26 with the pressure drop lower than 5kPa. Compared to the previous mixers, requiring the mixing lengths of 7∼17mm, the AWL-type microfluid mixer results in the 60% reduction of the mixing lengths. Due to the reduced mixing lengths within reasonable pressure drop ranges, the present micromixers have potentials for use in the miniaturized Micro-Total-Analysis-Systems($\mu$TAS).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.1
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• pp.25-33
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• 1998

In this paper, we describe a single-gate MESFET mixer at PCS(Personal Communication Service) frequency band. The PCS frequency band is 1965~2025 MHz in FR and 140 MHz in IF irrespectly. The design of the mixer was executed by microwave simulator, EEsof Libra. The matching network is consisted of rectangular inductor, MIM capacitor and open stub. The ma- nufacture work was accomplished by the micro-pen and wedge-bonder. The mixer showed $6.69\pm0.65$ dB of conversion gain, $-14.9\pm3.5$dB of RF reflection coefficient and 57.83 dB of LO/IF isolation at 10 dBm of LO power when LO frequency is 1855 MHz. When this mixer is used at PCS terminal, IF-amplifier which compensates the conversion loss of diode mixer may be omitted.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.10
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• pp.188-195
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• 2004

In this paper, we fabricated fluidic devices like micro-channel, pump, mixer and particular gas separator with the technology of stereolithouaphy using RP(rapid-prototyping). The fabricated fluidic devices are expected to be applied to develop Lab-on-a chip type liquid analyzer. Stereolithography technology seems effective for fabricating MEMS(Micro Electro Mechanical System) with complicated structure because it makes three dimensional fabrication possible but, exclusive devices are needed to be developed fur fabricating even more microscopic MEMS structure.

• Proceedings of the Materials Research Society of Korea Conference
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• 2005.05a
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• pp.84-84
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• 2005