• 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.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.642-649
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• 2021

Energy saving standard for buildings are strengthened, the application of exterior insulation finishing system and thickness of insulation materials are increasing. Most buildings with exterior insulation finishing system is applied organic insulating material. Organic insulating material have workability, economic feasibility, reduction in construction cost, and excellent thermal insulation performance. However, Organic insulating material is very vulnerable to heat, so when a fire occurs, rapid fire spread and toxic gas are generated, causing many casualties. Inorganic insulating material can be non-combustible performance, but it is heavy and has low thermal insulation performance. Mineral wool has higher thermal insulation performance than other types of inorganic insulating material, but mineral wool is disadvantageous to workability and vulnerable to moisture. Glass bubble are highly resistant to water and chemically stable substances. In addition, the density of the glass bubble is very low and the particles are spherical, fluidity is improved by the ball bearing effect. Glass bubbles can be used with cement-based ino rganic insulating material to impro ve the weight and thermal insulatio n perfo rmance o f cement-based inorganic insulation. This study produced a inorganic insulating materials were manufactured using cement-based materials and glass bubble. In order to evaluate the insulation performance and flame retardant performance of cement-based super light-weight inorganic insulating materials using with glass bubble, insulation performance or flame retardant and non-combustible performance were evaluated after manufacturing insulating materials using micro cement and two types of glass bubbles. From the test result, Increasing the mixing ratio of glass bubbles improved the insulation performance of cement-based super light-weight inorganic insulating materials, and when the mixing ratio of glass bubbles was 10%, it sho wed sufficient flame retardant and no n-co mbustible perfo rmance.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.315-316
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• 2002

Electrochemical discharge machining is a very recent technique for non-conducting materials such as ceramics and glasses. ECDM is conducted in the NaOH solution and the cathode electrode is separated from the solution by $H_2$ gas bubble. Then the discharge is appeared and the non-conductive material is removed by spark and some chemical reactions. In the ECDM technology, the $H_2$ bubble control is the most important factor to stabilize the discharging condition. In this paper, we proposed the discharge peak monitoring/ discharging duty feedback algorithms for the discharge stabilization and the feasibility of this algorithm is verified by various pattern machining in the constant preload conditions for the cathode electrode.

• KSTLE International Journal
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• v.3 no.2
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• pp.95-100
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• 2002

Electrochemical discharge machining is a very recent technique for non-conducting materials such as ceramics and glasses. ECDM is conducted in the NaOH solution and the cathode electrode is separated from the solution by H$_2$ gas bubble. Then the discharge is appeared and the non-conductive material is removed by spark and some chemical reactions. In the ECDM technology, the H$_2$ bubble control is the most important factor to stabilize the discharging condition. In this paper we proposed the discharge peak monitoring/discharging duty feedback algorithms fur the discharge stabilization and the feasibility of this algorithm is verified by various pattern machining in the constant preload conditions for the cathode electrode.

• Journal of the Korean Society of Visualization
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• v.4 no.2
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• pp.32-36
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• 2006

Recently there are many researches about single flow and two-phase flow phenomena in the mini and microchannel. But from this result the principle in the microchannel was not explained clearly. In this paper two-phase flow pattern was visualized in the micro-multi-branched-channel using a high speed camera. Microchannel was fabricated with PDMS and glass slide. The velocity profile was obtained by a Micro PIV. Then flow boiling at the near inlet area was occurred and vapor was moved in the micro-multi-branched-channel.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1186-1190
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• 2003

In this paper, a valveless bubble-actuated fluid micropump was has been developed and its performance was tested. The valveless micropump consists of the lower plate, the middle plate, the upper plate and a resistive heater. The lower plate includes the nozzle-diffuser elements and the double-chamber. Nozzle-diffuser elements and a double-chamber are fabricated on the silicon wafer by the DRIE(Deep Reactive Ion Etching) process. The lower plate also has inlet/outlet channels for fluid flow. The middle plate is made of glass and plays the role of the diaphragm. The chamber in the upper plate is filled with deionized water, and which contacts with the resistive heater. The resistive heater is patterned on a silicon substrate by Ti/Pt sputtering. Three plates and the resister heater are laminated by the aligner and bonded in the anodic bonder. Since the bubble is evaporated and condensed periodically in the chamber, the fluid flows from inlet to outlet with respect to the diffusion effect. In order to avoid backflow, the double chamber system is introduced. Analytical and experimental results show the validity of the developed double-chamber micropump.

• Composites Research
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• v.28 no.2
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• pp.70-74
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• 2015

In this paper, carbon nanotubes (CNTs) and micro glass bubbles (GBs) have been incorporated into a polyamide6 (PA6) matrix to impart thermoelectric properties. The spaces created in the matrix by GBs allows the formation of "segregated" CNT network. The tightly bound CNT network, if controlled properly, can serve as a conductive path for electron transport, while prohibiting phonon transport, which would provide an ideal configuration for thermoelectric applications. The CNTs and GBs were dispersed in a nylon-formic acid solution using horn sonication followed by coagulation in deionized water, and nanocomposite panels were fabricated using a hot press. The performance of nanocomposite panels was evaluated from thermal and electrical conductivities and Seebeck coefficient, and a thermoelectric figure of merit as high as 0.016 was achieved.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.8
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• pp.624-632
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• 2008

In this research, we developed new PDMS-glass based microbiochip consisted of the micromixer and microreactor for DNA ligation. The micromixer was composed of a straight channel integrated with nozzles and pillars, and the microreactor was composed of a serpentine channel. We coated the PDMS chip surface with the 0.25wt.% PVP solution to prevent the bubble generation which was caused by the hydrophobicity of the PDMS. The new micomixer was passive type and the mixing was enhanced by a convective diffusion using the nozzle and pillar. The 10.33mm long micromixer showed the good mixing efficiency of 87.7% at 500 l/min flow rate. We could perform the DNA ligation successfully in the microbiochip, and the ligation time was shortened from 4 hours in conventional laboratory method to 5 min in the microbiochip.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.518-522
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• 2013

This study investigatesthe coloration mechanism by identifying the factor that affects thered coloration of copper red glazesin traditional Korean ceramics. The characteristics of the reduction-fired copper red glaze's sections are analyzed using an optical microscope, Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX). The sections observed using an optical microscope are divided into domains of surface, red-bubble, and red band. According to the Raman micro spectroscopy analysis results, the major characteristic peak is identified as silicate in all three domains, and the intensity of $Cu_2O$ increases toward the red band. In addition, it is confirmed that the most abundant CuO exists in the glaze bubbles. Moreover, CuO and $Cu_2O$ exist as fine particles in a dispersed state in the surface domain. Thus, Cu combined with oxygen is distributed evenly throughout the copper red glaze, and $Cu_2O$ is more concentrated toward the interface between body and glaze. It is also confirmed that CuO is concentrated around the bubbles. Therefore, it is concluded that the red coloration of the copper red glaze is revealed not only through metallic Cu but also through $Cu_2O$ and CuO.

• Tribology and Lubricants
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• v.38 no.4
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• pp.121-127
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• 2022

This study presents the development of an integrated oil purification system consisting of moisture removal, oil flushing, and oil filtering devices. In this system, the oil flushing device is combined with a micro-bubble generator. Oil purification is necessary for ensuring the high performance of the lubricant through the efficient removal of contaminants and thus enables good maintenance of mechanical systems. The developed purification system removes moisture, varnish, and solid particles. Moreover, during oil purification, the oil flushing device separates foreign materials and contaminants remaining in the lubricating oil piping or mechanical systems. The microbubble generator, which is combined with the oil flushing device, can separate harmful contaminants, such as sludge, wear particles, and rust, from piping or lubrication systems through the cavitation effect. Moisture is removed using a double high-vacuum chamber, while sludge and varnish are removed via electro-absorption using a high-voltage generator. Additionally, the total maintenance cost of the system is reduced through the use of domestically fabricated cartridge filters composed of glass fiber and cellulose. The heater, which maintains the temperature of the lubricant at 60℃, can process 41,000 L of lubricant simultaneously. Multiple tests confirmed that the proposed integrated purification system exhibits good performance in oil flushing and removal of water and varnish.