ABSTRACT
Geometry of porous scaffolds is critical to the success of cell adhesion, proliferation, and differentiation in bone tissue engineering. In this study, the effect of scaffold geometry on osteogenic differentiation of MC3T3-E1 pre-osteoblasts in a perfusion bioreactor was investigated. Three geometries of oligolactide-HA scaffolds, named Woodpile, LC-1000, and LC-1400, were fabricated with uniform pore size distribution and interconnectivity using stereolithography (SL) technique, and tested to evaluate for the most suitable scaffold geometry. Compressive tests revealed sufficiently high strength of all scaffolds to support new bone formation. The LC-1400 scaffold showed the highest cell proliferation in accordance with the highest level of osteoblast-specific gene expression after 21 days of dynamic culture in a perfusion bioreactor; however, it deposited less amount of calcium than the LC-1000 scaffold. Computational fluid dynamics (CFD) simulation was employed to predict and explain the effect of flow behavior on cell response under dynamic culture. The findings concluded that appropriate flow shear stress enhanced cell differentiation and mineralization in the scaffold, with the LC-1000 scaffold performing best due to its optimal balance between permeability and flow-induced shear stress.
Subject(s)
Osteogenesis , Tissue Scaffolds , Hydrodynamics , Tissue Engineering/methods , Cell Differentiation , BioreactorsABSTRACT
In this paper, stereolithographic additive manufacturing of ceramic dental crowns is discussed and reviewed. The accuracy of parts in ceramic processing were optimized through smart computer-aided design, manufacturing, and evaluation. Then, viscous acrylic resin, including alumina particles, were successfully compounded. The closed packing of alumina particles in acrylic pastes was virtually simulated using the distinct element method. Multimodal distributions of particle diameters were systematically optimized at an 80% volume fraction, and an ultraviolet laser beam was scanned sterically. Fine spots were continuously joined by photochemical polymerization. The optical intensity distributions from focal spots were spatially simulated using the ray tracing method. Consequently, the lithographic conditions of the curing depths and dimensional tolerances were experimentally measured and effectively improved, where solid objects were freely processed by layer stacking and interlayer bonding. The composite precursors were dewaxed and sintered along effective heat treatment patterns. The results show that linear shrinkages were reduced as the particle volume fractions were increased. Anisotropic deformations in the horizontal and vertical directions were recursively resolved along numerical feedback for graphical design. Accordingly, dense microstructures without microcracks or pores were obtained. The mechanical properties were measured as practical levels for dental applications.
ABSTRACT
Three-dimensional (3D) microphotonic crystals with a diamond structure composed of titania microlattices were fabricated using ultraviolet laser lithography, and the bandgap properties in the terahertz (THz) electromagnetic-wave frequency region were investigated. An acrylic resin paste with titania fine particle dispersions was used as the raw material for additive manufacturing. By scanning a spread paste surface with an ultraviolet laser beam, two-dimensional solid patterns were dewaxed and sintered. Subsequently, 3D structures with a relative density of 97% were created via layer lamination and joining. A titania diamond lattice with a lattice constant density of 240 µm was obtained. The properties of the electromagnetic wave were measured using a THz time-domain spectrometer. In the transmission spectra for the Γ-X direction, a forbidden band was observed from 0.26 THz to 0.44 THz. The frequency range of the bandgap agreed well with calculated results obtained using the planeâ»wave expansion method. Additionally, results of a simulation via transmission-line modeling indicated that a localized mode can be obtained by introducing a plane defect between twinned diamond lattice structures.
ABSTRACT
Three-dimensional fractals called the Menger sponge, with a fractal dimension D=log(20/log(3, were fabricated from epoxy resin by stereolithography. Clear attenuation of both reflection and transmission intensity was observed at 12.8 GHz for a cubic specimen with an edge size of 27 mm that was constructed up to the third stage of the self-similar patterns. The electromagnetic field was found to be confined in the central part of the specimen at this frequency. The localization is not caused by the presence of a photonic band gap as in photonic crystals but should be attributed to a singular photon density of states realized in the fractal structure. This is the first report on such localization of electromagnetic waves in three-dimensional fractal cavities.