• Design & Manufacturing
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• v.14 no.1
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• pp.36-41
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• 2020

Recently, due to the development of MEMS technology, researches for the production of effective micro structures and shapes have been actively conducted. However, the process technology based on chemical etching has a number of problems such as environmental pollution and time problems due to multi-process. Various processes to cope with this process are being studied, and one of the mechanical etching processes is the powder blasting process. This process is a method of spraying fine particles, which has the advantage of being an effective process in manufacturing hard brittle materials. However, it is also a process that adversely affects the material surface roughness and material properties due to the impact of the injection of fine particles. In this study, after fabricating micro-channels in fused silica glass with excellent optical properties among the hard brittle materials, we used the nano indentation system to analyze the micro parts using nano-particles as well as machinability and surface roughness analysis of the processed surface. The analysis was performed for the effective processing of powder blasting.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.10 s.253
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• pp.935-941
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• 2006

Many important properties in colloidal systems are usually determined by surface charge $({\zeta}-potential)$ of the contacted solid surface. In this study, ${\zeta}-potential$ of glass ${\mu}-channel$ was evaluated from the electro-osmotic velocity distribution. The electro-osmotic velocity inside a glass f-channel was measured using a micro-PIV velocity field measurement technique. This evaluation method is more simple and easy to approach, compared with the traditional streaming potential technique. The ${\zeta}-potential$ in the glass ${\mu}-channel$ was measured fur two different mole NaCl solutions. The effect of an anion surfactant, sodium dodecyl sulphate (SDS), on the electro-osmotic velocity and f-potential in the glass surface was also studied. In the range of $0{\sim}6mM$, the surfactant SDS was added to NaCl solution in few different mole concentrations. As a result, the addition of SDS increases ${\zeta}-potential$ in the surface of the glass ${\mu}-channel$. The measured $\zeta-potential$ was found to vary from -260 to -70mV. When negatively charged particles were used, the flow direction was opposite compared with that of neutral particles. The ${\zeta}-potential$ has a positive sign for the negative particles.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.220-223
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• 2005

The rapid prototyping (RP) technology has been advanced for various applications such as verification of design, functional test. However, many RP machines still have low accuracy and limitation of applications for various materials. In this research, a hybrid RP system was developed to improve precision of micro parts. This hybrid system consists of deposition and material removal process by mechanical micro machining to fabricate nano composites using photo-curable polymer resin with various nano particles. In this work, using hybrid RP process with Multi-Walled Carbon Nano Tube (MWCNT) and hydroxyapatite, micro parts were fabricated. The precision of parts was evaluated based on the original CAD design, and to see the effect of nano particles on mechanical properties, tensile strength was measured. From the results of experiments, it was confirmed that the part made by hybrid process had higher precision, and the addition of nano particles improved mechanical properties.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.12
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• pp.134-141
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• 2002

The ER fluid can be one of efficient materials in ultraprecision polishing for optics, ceramics and semiconductors because of electrically controllable apparent viscosity. To finish small 3 dimensional structures such as the aspherical surface in optical elements, the possible arrangement of a tool, workpiece and auxiliary electrode is described. We examined the influence of the addition of a few abrasive particles on the performance of the ER fluid by measuring yield stress, and observed the behavior of abrasive particles in the ER fluid by a CCD camera, which is also theoretically predicted from the electromechanical principles of particles. On the basis of the above results, the steady flow analysis around the rotating micro tool is worked out considering the non-uniform electric field. Finally, Pyrex glass is polished using the mixture of the ER fluid and abrasive particles, and the effect of the electric field strength is evaluated.

• Journal of Korea Foundry Society
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• v.15 no.6
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• pp.588-595
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• 1995

SiC particles reinforced Mg-Zr, Mg-Zn and Mg-Zn-Zr composites were manufactured by Rheocompocasting method. Effects of Zn, Zr addition on microstructures and hardness were investigated by using the micro Vickers hardness tester, the optical and scanning electron microscopy. By the Zr addition to the pureMg/SiCp composites, SiC particles become more homogeneously dispersed and grain refined so that the micro hardness of the composite increased. In case of Zn addition, although grain refinement and homogeneous dispersion effects of SiC particles were not obtained, hardness was more increased than the only Zr added composite by the formation of many Mg-Zn intermetallic compounds at grain boundary. In the Mg-Zn-Zr/SiCp composite, the highest value of hardness was obtained by triple effects such as grain refining, dispersion hardening of SiC particles and Mg-Zn compounds.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.679-682
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• 2008

The particle which has two different characteristics on both sides is called Janus particle which is emerging as a key material in microscale transport systems. For example, if one hemisphere has polarity and the other does not, then nonpolar sides would attract each other so that a complex cluster is formed. Thus, this fascinating material can be used as an element of twisting ball panel display, complex micro-scale clusters, drug delivery unit, and active detecting beads. The keywords in developing Janus particle are size and uniformity. Former researches solved uniformity but downsizing still remains a problem. There are three methods to generate small size particles in microchannels: co-flowing, cross-flowing, and elongational flows. In this research, we generate Janus particles smaller than 10-${\mu}$m in diameter using elongational flow in microchannels. And we use UV initiator with Hydrogen UV source to solidify micro size particles. One hemisphere of the particle is coated with rhodamin for visualization.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.227-230
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• 2002

New polishing technique for small parts has been tried out using the principle of particle electromechanics. Common fine abrasives such as alumina, diamond, silicon carbide are dielectric materials which are polarized under an electric field, and a non-uniform electric field makes abrasive particles translate along the field line. Using this principle, We make abrasive particles aggregate in the vicinity of the micro tool which is fir the surface finishing of a small part without contact with it. The behavior of particles is optically measured, and the machined depth of glass is examined.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03b
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• pp.31-31
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• 2010

Nano particles (10nm $SiO_2$) were silane-treated in order to modify the surface characteristics in a epoxy nanocomposite. Then, micro particles ($3{\mu}m$ SiO2) were poured into the epoxy nanocomposite using various mixing process and epoxy/micro-and-nanomixed composites (EMNC) were prepared. The thermal (Tg) and mechanical (tensile and flexural strength) properties were measured by DSC, DMA and UTM and the data was estimated by Weibull plot.

• Structural Engineering and Mechanics
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• v.61 no.3
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• pp.381-387
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• 2017

In this paper we investigate the theory of micropolar thermoelastic bodies whose micro-particles possess microtemperatures. We transform the mixed initial boundary value problem into a temporally evolutionary equation on a Hilbert space and after that we prove the existence and uniqueness of the solution. We also approach the study of the continuous dependence of solution upon initial data and loads.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.5 no.4
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• pp.21-26
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• 2006

Characteristics of texture and groove precision lapping plate are experimentally investigated by Measuring frictional forces. It is found that the frictional coefficient decreases as the embedding of diamond particles progresses. The groove precision lapping plate with concentric micro-channels indicates superior capability in embedding micrometer-sized diamond particles and uniformity in diamond embedding compared with the texture precision lapping plate with a series of circular micro-channels.