• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.8
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• pp.731-736
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• 2016

Three-dimensional (3D) high-aspect-ratio (HAR) microstructures for biomedical applications (e.g., microneedle, microadhesive, etc.) are microfabricated using the hybrid ultraviolet (UV) lithography in which inclined, rotational, and reverse-side UV exposure processes are combined together. The inclined and rotational UV exposure processes are intended to fabricate tapered axisymmetric HAR microstructures; the reverse-side UV exposure process is designed to sharpen the end tip of the microstructures by suppressing the UV reflection on a bottom substrate which is inevitable in conventional UV lithography. Hybrid UV lithography involves fabricating 3D HAR microstructures with an epoxy-based negative photoresist, SU-8, using our customized UV exposure system. The effects of hybrid UV lithography parameters on the geometry of the 3D HAR microstructures (aspect ratio, radius of curvature of the end tip, etc.) are measured. The dependence of the end-tip shape on SU-8 soft-baking condition is also discussed.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.10a
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• pp.14-17
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• 2006

This paper describes a novel processing technique for fabrication of polymer-derived SiCN (silicone carbonitride) microstructures for super-temperature MEMS applications. PDMS (polydimethylsiloxane) mold is fabricated on SU-8 photoresist using standard UV photolithographic process. Liquid precursor is injected into the PDMS mold. Finally, solid polymer structure is cross-linked using HIP (hot isostatic pressure) at $400^{\circ}C$, 205 bar Optimum pyrolysis and anneal ins conditions are determined to form a ceramic microstructure capable of withstanding over $1400^{\circ}C$. The fabricated SiCN ceramic microstructure has excel lent characteristics, such as shear strength (15.2 N), insulation resistance ($2.163{\times}10^{14}\;{\Omega}$) and BDV (min. 1.2 kV) under optimum process condition.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.788-790
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• 2003

Closed-cell type barrier ribs of PDP were formed by capillary molding process using molds prepared by inclined UV lithography process. Various types of molds with different inclined angles were prepared by patterning SU-8 thick photoresist film and casting with PDMS. The ribs with various type cells were successfully formed by the process. The effects of inclined angle on the distortion of barrier ribs during sintering were investigated. The results indicated that the barrier ribs with a draft angle and dimensional change does not affect the distortion of the barrier ribs during sintering, suggesting that the closed-cell must be isotropic in sintering shrinkage.

• Journal of the Optical Society of Korea
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• v.13 no.4
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• pp.478-483
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• 2009

An optical sheet with a cone array is designed, simulated, and fabricated in order to substitute the dual crossed prism sheets in the edge-type LCD backlight. The optimum structure of cone textures that is compatible with the dual crossed prism sheets was obtained by simulating the backlight installed with the cone array optical sheet. A SU-8 photoresist films of thickness $30{\sim}50{\mu}m$ were spin-coated on a polyethylene terephtalate film (PET), and the cone texture array was formed by using the diffuse lithography that employed a photomask with circular patterns and an optical diffuser.

• Laser Solutions
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• v.11 no.2
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• pp.26-32
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• 2008

Micro lens array (MLA) is widely used in information technology (IT) industry fields, for examples such as a projection display, an optical power regulator, a micro mass spectrometer and for medical appliances. Recently, MLA have been fabricated and developed by using a reflow method, micro etching, electroplating, micromachining and laser local heating. Laser local thermal-expansion (LLTE) technology demonstrates the formation of microdots on the surface of polymer substrate, in this paper. We have also investigated the new direct fabrication method of placing the MLA on the surface of a SU-8 photoresist layer. We have obtained the 3D shape of the micro lens processed by UV laser irradiation and have experimentally verified the optimal process conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.9
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• pp.1429-1434
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• 2004

Immunoassay is one of the important analytical methods for clinical diagnoses and biochemical studies, but needs a long time, troublesome procedures and expensive reagents. In this study, therefore, we propose the micro filter chip with microbeads for immunoassay, which has pillar structures. The advantage of the proposed micro filter chip is to use simple fabrication process and cheap materials. The mold was made by the photolithography technique with Si wafer and negative photoresist SU-8. The replica was made of PDMS, bonded on the pyrex glass. The micro filter chip consists of inlet channel, filter chamber and outlet channel. HBV (Hepatitius B virus) monoclonal antibody (Ag1) labeled with biotin were immobilized onto streptavidin coated beads of 30∼50 $\mu$m size. Fluorescein isothiocyanate (FITC)-labeled HBV monoclonal antibody (Ag8) was used to detect HBsAg (Hebatitis B virus surface Antigen), and fluorescence intensity was monitored by epi-fluorescence microscope. In this study, the immune response of less than 30 min was obtained with with the use of 100 $m\ell$ of sample.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.238-242
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• 2005

In this work, Polydimethylsiloxane (PDMS) and SU-8 (Microchem, USA) photoresist were used to make the microchannel by soft lithographic method. To investigate the effects of external voltages and widths of the microchannel, we made the microchannel by soft lithographic method. To investigate the effects of external voltages and widths of the microchannel, we made the microchannel with various widths: $100{\mu}m,\;200{\mu}m$ and $300{\mu}m$. And each micorchannel was supplied with external voltage, respectively. As a result, the fluid velocity increased with an increase of the external voltage at the same width. It was speculated that the electrical double layer was condensed and the zeta potential increased with increase of the external voltage. The fluid velocity increased with the microchannel width increase at the same external voltage. It is concluded that the resistance in the microchannel decreased as the microchannel width increased.

• Coupled systems mechanics
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• v.5 no.4
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• pp.355-369
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• 2016

Changes in chemical structure have profound effects on the physical properties of epoxy-based materials, and eventually affect the durability of the entire system. Microscopic structural voids generally existing in the epoxy cross-linked networks have a detrimental influence on the epoxy mechanical properties, but the relation remains elusive, which is hindered by the complex structure of epoxy-based materials. In this paper, we investigate the effect of structural voids on the epoxy-based materials by using our developed mesoscale model equipped with the concept of multiscale modeling, and SU-8 photoresist is used as a representative of epoxy-based materials. Developed from the results of full atomistic simulations, the mesoscopic model is validated against experimental measurements, which is suitable to describe the elastic deformation of epoxy-based materials over several orders of magnitude in time- and length scales. After that, a certain quantity of the structure voids is incorporated in the mesoscale model. It is found that the existence of structural voids reduces the tensile stiffness of the mesoscale epoxy network, when compared with the case without any voids in the model. In addition, it is noticed that a certain number of the structural voids have an insignificant effect on the epoxy elastic properties, and the mesoscale model containing structural voids is close to those found in real systems.

• Journal of Sensor Science and Technology
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• v.15 no.1
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• pp.53-57
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• 2006

This paper describes a novel processing technique for fabrication of polymer-derived SiCN (silicone carbonitride) microstructures for super-temperature MEMS applications. PDMS (polydimethylsiloxane) mold is fabricated on SU-8 photoresist using standard UV photolithographic process. Liquid precursor is injected into the PDMS mold. Finally, solid polymer structure is cross-linked using HIP (hot isostatic pressure) at $400^{\circ}C$, 205 bar. Optimum pyrolysis and annealing conditions are determined to form a ceramic microstructure capable of withstanding over $1400^{\circ}C$. The fabricated SiCN ceramic microstructure has excellent characteristics, such as shear strength (15.2 N), insulation resistance ($2.163{\times}10^{14}{\Omega}$) and BDV (min. 1.2 kV) under optimum process condition. These fabricated SiCN ceramic microstructures have greater electric and physical characteristics than bulk Si wafer. The fabricated SiCN microstructures would be applied for supertemperature MEMS applications such as heat exchanger and combustion chamber.

• 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.