• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.663-664
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• 2007

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.1
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• pp.45-49
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• 2006

A nano-stereolithography (NSL) process has been developed for the fabrication of three-dimensional (3D) micro-devices with high spatital resolution of approximately 100 nm. In the NSL process, a complicated 3D structure can be created by stacking layer-by-layer, so it does not require any sacrificial layer or any supporting structure. A laminated layer was fabricated by means of solidifying liquid-state monomers using two-photon absorption (TPA) which was induced by a femtosecond laser. When the fabrication of a 3D stacked structure was finished, unsolidified liquid resins were rinsed by ethanol to develop the fabricated structures; then, the polymerized structure was only left on the glass substrate. Through this work, several 3D microstructures such as a micro-channel, shell structures, and photonic crystals were fabricated to evaluate the possibility of the developed system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.525-526
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• 2006

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.605-606
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.657-658
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• 2010

• Journal of the Korean Society for Precision Engineering
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• v.30 no.3
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• pp.340-348
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• 2013

In Projection Stereolithography Apparatus (PSLA), Digital Micromirror Device (DMD) and Liquid Crystal Display (LCD) are used as a beam pattern generator. The DMD shows high resolution, but it is mostly applied in micro stereolithography due to high cost and fabricable area. In LCD, the size of pattern beam is freely controlled due to various panel sizes. The LCD, however, has some limitations such as short life time by the high power light source, non-uniform light intensity of pattern beam and low transmittance of UV-light. To solve these problems in LCD-based PSLA, a Scanbeam-SLA with LCD of 19 inches and visible LED-array is developed. In this system, the light module works like a scanner for uniform illumination. The system configuration, working principle and fabrication examples are addressed in this study.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.173-174
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• 2006

Understanding chondrocyte behavior inside complex, three-dimensional environments with controlled patterning of geometrical factors would provide significant insights into the basic biology of tissue regenerations. One of the fundamental limitations in studying such behavior has been the inability to fabricate controlled 3D structures. To overcome this problem, we have developed a three-dimensional microfabrication system. This system allows fabrication of predesigned internal architectures and pore size by stacking up the photopolymerized materials. Photopolymer SL5180 was used as the material for 3D scaffolds. The results demonstrate that controllable and reproducible inner-architecture can be fabricated. Chondrocytes harvested from human nasal septum were cultured in two kinds of 3D scaffolds to observe cell adhesion behavior. Such 3D scaffolds might provide effective key factors to study cell behavior in complex environments and could eventually lead to optimum design of scaffolds in various tissue regenerations such as cartilage, bone, etc. in a near future.

• Polymer(Korea)
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• v.29 no.4
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• pp.418-421
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• 2005

Three-dimensional (3D) microfabrication process using two-photon polymerization (TPP) is developed to fabricate the curved microstructures in a layer, which can be applied potentially to optical MEMS, nano/micro-devices, etc. A 3D curved structure can be expressed using the same height-contours that are defined by symbolic colors which consist of 14 colors. Then, the designed bitmap figure is transformed into a multi-exposure voxel matrix (MVM). In this work a multi-exposure voxel matrix scanning method is used to generate various heights of voxels according to each laser exposure time that is assigned to the symbolic colors. An objective lens with a numerical aperture of 1.25 is employed to enlarge the variation of a voxel height in the range of 1.2 to 6.4 um which can be controlled easily using the various exposure time. Though this work some 3D curved micro-shapes are fabricated directly to demonstrate the usefulness of the process without a laminating process that is generally required in a micro-stereolithography process.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.1
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• pp.138-144
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• 2008

Micro-machining of a brittle material such as glass, silicon, etc., is important in micro fabrication. Particularly, micro-abrasive jet machining (${\mu}-AJM$) has become a useful technique for micro-machining of such materials. The ${\mu}-AJM$ process is mainly based on the erosion of a mask which protects brittle substrate against high velocity of micro-particle. Therefore, fabrication of an adequate mask is very important. Generally, for the fabrication of a mask in the ${\mu}-AJM$ process, a photomask based on the semi-conductor fabrication process was used. In this research a rapid mask fabrication technology has been developed for the ${\mu}-AJM$. By scanning the focused UV laser beam, a micro-mask pattern was fabricated directly without photolithography process and photomask. Two kinds of mask patterns were fabricated using SU-8 and photopolymer (Watershed 11110). Using fabricated mask patterns, abrasive-jet machining of Si wafer were conducted successfully.

• The Journal of Advanced Prosthodontics
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• v.9 no.6
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• pp.463-469
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• 2017

PURPOSE. To evaluate the fit of a three-unit metal framework of fixed dental prostheses made by subtractive and additive manufacturing. MATERIALS AND METHODS. One master model of metal was fabricated. Twenty silicone impressions were made on the master die, working die of 10 poured with Type 4 stone, and working die of 10 made of scannable stone. Ten three-unit wax frameworks were fabricated by wax-up from Type IV working die. Stereolithography files of 10 three-unit frameworks were obtained using a model scanner and three-dimensional design software on a scannable working die. The three-unit wax framework was fabricated using subtractive manufacturing (SM) by applying the prepared stereolithography file, and the resin framework was fabricated by additive manufacturing (AM); both used metal alloy castings for metal frameworks. Marginal and internal gap were measured using silicone replica technique and digital microscope. Measurement data were analyzed by Kruskal-Wallis H test and Mann-Whitney U-test (${\alpha}=.05$). RESULTS. The lowest and highest gaps between premolar and molar margins were in the SM group and the AM group, respectively. There was a statistically significant difference in the marginal gap among the 3 groups (P<.001). In the marginal area where pontic was present, the largest gap was $149.39{\pm}42.30{\mu}m$ in the AM group, and the lowest gap was $24.40{\pm}11.92{\mu}m$ in the SM group. CONCLUSION. Three-unit metal frameworks made by subtractive manufacturing are clinically applicable. However, additive manufacturing requires more research to be applied clinically.