Dendritic electrodes composed of yttria stabilized zirconia (YSZ) and nickel oxide (NiO) were successfully fabricated by using micro stereolithography for solid oxide fuel cells. The dendritic structures constructed from micrometer order ceramic rods with coordination numbers of 4, 6, 8, and 12 were designed in computer graphic application. Range of aspect ratios determined by rod diameters and lengths was varied from 0.75 to 3.00. Gaseous fluid permeabilities in the dendritic lattices were simulated and visualized by using finite volume methods. The dendritic lattice with 12 coordination number was verified to exhibit the largest surface area and smooth fluid transparent characteristics. The optimized dendritic structure of 100 μm in lattice constant was fabricated by using micro stereolithography. Composite precursors of acrylic resin and nanometer sized YSZ and Ni particles were dewaxed at 600 °C for 2 hs and sintered at 1350-1450 °C for 2 hs. Microstructures were observed by using optical and scanning electron microscope.
Magnetophotonic crystals with periodic arranged of permeability can reflect terahertz waves through Bragg diffraction. The micrometer order photonic crystals were fabricated by stereolithographic method. In this process, acrylic resin including metallic and oxide glass particles was spread on a polyethylene substrate with 10 μm in layer thickness. Then a two dimensional pattern was formed by illuminating visible laser with 405 nm in wavelength. Through stacking layer process, a micrometer order three dimensional structure was constructed. Metallic and oxide glass composite material was obtained through heat treatment. The amorphous structure of the metallic glass was kept by low temperature heating process. The transmission spectrum of terahertz wave for the fabricated crystals was measured by terahertz time domain spectroscopy.
Fractal patterns composed of hard alloys were created on light metal substrates for surface stress control by using a laser scanning stereolithography and reaction diffusion treatments. Photo sensitive urethane resin including pure copper particles of 75 μm in average diameter was spread on tensile specimens of pure aluminum with 100 μm in layer thickness. Hilbert fractal curves with self-similarities of 1, 2 and 3 in stage number were drawn by single stroke scanning of an ultra violet laser beam of 100 μm in spot size. Self similar patterns composed of copper aluminides were created through heat treatments at 600°C above eutectic temperature for 8 hs in an argon atmosphere. Microstructures and composite distributions were observed by a scanning electron microscopy and energy dispersive X-ray spectroscopy, Measured mechanical properties by tensile tests were compared with simulated ones by finite element method. Above mentioned fractal patterning of hard alloys can be expected to strengthen the light metals efficiently through controlling of surface stress distributions.
Graded porous scaffolds were fabricated via stereolithography. For the geometrical design, an inverse body-centered-cubic structure and four-coordinate lattices graded structures were considered. In the manufacturing process, a photosensitive resin containing hydroxyapatite particle was spread on a substrate and scanned to create two-dimensional images. The precursors were obtained after layer stacking processes. A full ceramic sample was obtained through heat treatment processes. Fine hydroxyapatite microstructures without cracks were observed by using a scanning electron microscope. This result shows that stereolithography is a novel technology that can be used to fabricate bio-scaffolds. The successfully manufactured bone substitute and the strictly designed bioscaffold structures can be used to promote appropriate biochemical reactions and body fluid circulation in the near future through tissue engineering.