Molded Micro Research Articles

X-ray tomography of powder injection moulded micro parts using synchrotron radiation

Powder injection moulding is one of the most promising replication methods for the mass production of metal and ceramic micro parts. The material for injection moulding, a so-called feedstock, consists of thermoplastic binder components and inorganic filler with approximately equal volume fractions. Injection moulding of the feedstock leads to a green part that can be processed to a dense metal or ceramic micro part by debinding and sintering.During the injection moulding process extremely high shear rates are applied. This promotes the separation of powder and binder leading to a particle density variation in the green part causing anisotropic shrinkage during post-processing. The knowledge of introducing density gradients and defects would consequently allow the optimization of the feedstock, the moulding parameters and the validation of a simulation tool based on the Dissipative Particle Dynamics which is currently under development, as well.To determine the particle density and defect distribution in micro parts synchrotron radiation tomography in absorption mode was used. Due to its parallel and monochromatic character a quantitative reconstruction, free of beam hardening artifacts, is possible. For the measurement, bending bars consisting of dispersed fused silica particles in a polymeric matrix were used. The presented results using this set-up show that crucial defects and density variations can be detected.

Analysis of Residual Stresses in Micro Powder Injection Moulded Micro Bending Specimens Made of Zirconia

Analysis of the residual stress state, the microstructure and surface topography of ceramic microcomponents made of Y2O3-stabilized ZrO2 produced by micro powder injection moulding were performed. During the production of the microspecimens sintering conditions were varied. The measurement of residual stresses has been carried out using the MAXIM (MAterials XRay IMaging) diffractometer at HASYLAB beamline G3 at DESY in Hamburg (Germany). The microstructure and surface topography of differently moulded specimens were examined using a scanning electron microscope (SEM) and a confocal white light microscope type NANOFOCUS. The findings are used to establish correlations between process parameters and characteristics of the microcomponents. These will allow to improve the production process with respect to the mechanical properties of the microcomponents.

Low-wavefront aberration and high-temperature stability molded micro Fresnel lens

A high-diffraction efficiency (>50%), small lens diameter (0.5 mm phi ), short focal length (1 mm), and thin (0.25 mm) molded micro Fresnel lens suitable for compact optical devices is discussed. The device is fabricated by means of a photopolymerization process using a UV-curable resin. By adopting glass as the substrate, low-wavefront aberration ( >