Papers by Keyword: Microstereolithography

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Authors: Seung Jae Lee, Byung Kim, Geun Bae Lim, Sung Won Kim, Jong Won Rhie, Dong Woo Cho
Abstract: This paper compares the characteristics of chondrocyte adhesion on two types of threedimensional (3-D) scaffold: types A and B. These 3-D scaffolds can be repeatedly constructed with the same dimensions using microstereolithography, a system that allows the fabrication of predesigned internal structures, such as pore size and porosity, by stacking the photopolymerized material. In tissue engineering, chondrocyte adhesion to a scaffold should have a major effect on the regeneration of cartilage. In this regard, we evaluated chondrocyte adhesion to two types of scaffold and found that chondrocyte adhesion was better on the type B scaffold than on the type A, demonstrating the importance of scaffold geometry in chondrocyte adhesion.
Authors: Robert Bail
Abstract: A visible light absorber containing the colorants Quinoline Yellow, Azorubine and Green S was used as an additive for process control in a microstereolithography process operating under visible light. An aqueous solution containing the three dyestuffs was added in concentrations of 0.1 to 5.0 wt% to a photopolymerizable hydrogel. A series of experiments showed that a minimum concentration of 2.0 wt% of the dye solution and an exposure dose of 100 mJ/cm2 were prerequisites to produce utilizable results on the setup used. Full curing and excellent cure-depth control were only achieved at the highest of the tested concentrations of 5.0 wt% dye solution. The working curve derived for the latter concentration suggested that an exposure dose of 147.6 mJ/cm2 was required to cure an exactly 100-micrometer thin layer. Furthermore, addition of the absorber improved the elasticity of the produced structures from an average modulus of 38.2 MPa at 2% to 30.6 MPa at 5% dye concentration. These results demonstrated that broadband absorbers could be useful as low-cost additives for cure-depth control in photopolymerizable hydrogel materials.
Authors: Daisuke Sano, Soshu Kirihara
Abstract: We designed micro-scale photonic crystal with or without graded lattice spacing composed of copper to control Terahertz (THz) waves. Designed structures were fabricated by using micro-stereolithography. By proper dewaxing and sintering process, pure copper photonic crystals were obtained. Transmission properties of THz waves propagating through the photonic crystals were measured by THz time-domain spectroscopy. Measured results showed good agreements with the simulated results.
Authors: Guang Shen Xu, Huan Pan, Xun Ming Ma, Sheng Luo, Rong Hua Qiu
Abstract: The non-uniformity distribution of UV light intensity in the imaging plane of integral micro-Stereolithography (µSL) System will induces serious distortion of object in building process, and the building accuracy of the SL system can not be assured. To obtain uniformity distribution of UV light intensity, experimental investigations were performed to research the relationship of UV light intensity with position (x,y) in the imaging plane and gray-scale z of the pattern in the integral µSL System. Based on the experiment results, the model of UV light intensity was established with least squares method. According to the model, for a given point in the imaging plane of the µSL system, the UV light intensity can be changed with varying the gray-scale of the pattern. As a result, Uniformity UV light intensity distribution is obtained in the imaging plane, and the difference between maximum and minimum value of UV light intensity is 0.06µW/cm2. The uniformity UV light intensity distribution provides a foundation for building accurate microstructures with the µSL system.
Authors: Masaru Kaneko, Soshu Kirihara
Abstract: The diamond photonic crystals with the periodic arrangement of high dielectric constant (ε=100) were fabricated, and photonic band gap properties in the millimeter waveguides were investigated. Acrylic diamond lattice structures with TiO2 dispersion at 40 vol. % were fabricated by Micro-stereolithography. The forming accuracy was 10m. After sintering process, TiO2 diamond lattice structures are obtained. The relative density reached 96%. The millimeter wave transmittance properties were measured with network analyzer and W-band millimeter waveguide. The band gap was measured between 90 GHz and 110 GHz in the Γ-X <100> direction, which was well agreed with the results calculated by the plane wave expansion method and simulated by the Transmission Line Modeling method.
Authors: Sung Hoon Kim, Dae Jun Jung, Jae Young Joo, Sung Ho Jeong
Abstract: The curing characteristics of a photocurable resin are critical factors that often decide the ultimate resolution and structural sharpness of a final product fabricated by microstereolithography (μ-STL). In this study, we investigated the curing characteristics of the FA1260T photopolymer under a visible laser light of 442nm wavelength. Modification of the curing property of the FA1260T is attempted to reduce the cure depth (Dc) by adding a radical quencher to the resin. Also, an organic solvent was used to reduce the resin viscosity for an improvement of the flatness of the liquid surface during layer-by-layer curing. As a result, the minimum Dc has been reduced over a factor of 3 with no abrupt increase. Samples of three dimensional microstructures fabricated using the modified FA1260T are presented.
Authors: Guang Shen Xu, Xun Ming Ma, Huan Pan, Song Qiao Hu
Abstract: In order to fabricate micro/meso structures, a novel micro-stereolithography (SL) system with dynamic pattern generator using digital micro-mirror device (DMD) has been investigated. The micro-stereolithography system solidifies photo-sensitive resin with image mask generated by dynamic pattern generator. The micro-stereolithography system is made up of dynamic pattern generator, recoating system and control system. The dynamic pattern generator consists of parabolic concentrator, UV lamp, collimating lens, shutter, DMD and its control, lens and computer. UV light intensity distribution in the imaging plane is investigated. Uniformity UV light intensity distribution is obtained in the imaging plane with changing small area’s gray-scale, and the difference between maximum and minimum value of UV light intensity is 0.4µW/cm2. Small size parts with intricate microstructures have been fabricated with the novel SL system. Compared with laser scanning SL system, the advantage of the novel micro-SL system is that the new SL system can build small objects having micro-structures with low cost in shorter time. The novel micro-SL system provides a solution to the problem that has hampered the progress of SL process into high resolution with low cost.
Authors: Jin Woo Lee, Byung Kim, Geun Bae Lim, Dong Woo Cho
Abstract: Although tissue engineering is an area with great potential, it still has few applications due to the lack of biocompatible, biodegradable materials with suitable mechanical properties. Recently, several biodegradable materials were developed, of which poly(propylene fumarate (PPF) is one of the most notable. It degrades into fumaric acid and propylene glycol, which are both biocompatible products. Microstereolithography is a new technology that can be used to fabricate free-form 3-D microstructures by dividing a desired shape into many slices of a given horizontal thickness. This technology requires a low-viscosity resin to fabricate fine structures. However, the viscosity of PPF is too high to fabricate 3D structures using microstereolithography. Therefore, we reduced the viscosity of the resin by adding diethyl fumarate (DEF). Then, we added a photoinitiator to photo-crosslink the DEF/PPF resin, and fabricated 2.5-D scaffolds using our system. We confirmed that microstereolithography technology is effective in scaffold fabrication. The fabricated 2.5-D scaffolds were seeded with fibroblasts and the cells attached well after seeding.
Authors: Soshu Kirihara, Toshiki Niki, Masaru Kaneko
Abstract: Fabrication and terahertz wave properties of alumina micro photonic crystals with a diamond structure were investigated. The three-dimensional diamond structure was designed on a computer using 3D-CAD software. Acrylic diamond structures with alumina particles dispersion were formed by using micro-stereolithography. Fabricated precursors were dewaxed and sintered in the air. The electromagnetic wave properties were measured by terahertz time-domain spectroscopy. A complete photonic band gap was observed at the frequency range from 0.40 to 0.47 THz, and showed good agreement with the simulation results calculated by the plane wave expansion method. Moreover, a localized mode was obtained by introducing a plane defect between twinned diamond structures. The one-way transmission of the electromagnetic wave was realized by using this twinned photonic crystal with the graded diamond structure. They corresponded to the simulation by the transmission line modeling (TLM) method.
Authors: Seung Jae Lee, Byung Kim, Jin Sang Lee, Sung Won Kim, Min Soo Kim, Joo Sung Kim, Geun Bae Lim, Dong Woo Cho
Abstract: 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 3D microfabricated scaffolds. The results demonstrate that controllable and reproducible inner-architecture can be fabricated. Chondrocytes from human nasal septum were cultured in 3D scaffolds for 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.
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