Fujio Tsumori

Coupled, macro-micro modeling for hot deformation and sintering.

Abstract Coupled, macro–micro modeling is proposed to describe hot deformation and sintering behavior of materials at the elevated temperature. Micro-model for description of microstructure evolution is coupled in the hierarchical structure with the macro-model for deformation of structural members or specimens. Owing to the homogenization theory and the selected unit-cell model, hot pressing as well as hipping processes can be quantitatively described by the present method. Direct coupling among the elasto-creep deformation, the thermal transient and the diffusion process enables us to construct the theoretical frame for quantitative description of various material behavior at the elevated temperature. Numerical examples are shown to demonstrate the validity and effectiveness of the present methodology.

Development of improved solid oxide fuel cell electrolyte sheet by microimprinting for layered material

At present, the solid oxide fuel cell (SOFC) is attracting much attention because it possesses the highest power generation efficiency among many types of fuel cell, and SOFC emits only water that does not harm the environment. Recently, the electrolyte structure for SOFC has been processed into various forms to increase the efficiency of SOFC. In this work, we tried to improve the performance of SOFC by changing the mesostructure on the interfaces between the electrolyte and electrodes. This hundred-micrometer-scaled mesostructure has been proposed to increase the reaction on the interfaces. However, there has been no effective method of fabricating the cells with the microstructure along the interfaces. We have already proposed the micro powder imprint (?PI) method to create fine patterns on ceramic samples. In this study, the ?PI method for layered material was newly developed to fabricate the micropatterns on both sides of an electrolyte sheet. The optimization of process parameters, such as compounding ratio, debinding temperature, and sintering temperature, was examined to obtain desired wavy patterns on both surfaces of the electrolyte sheet.

Magnetic actuator using interaction between micro magnetic elements

This paper reports a new type magnetic actuator using interaction between micro magnetic elements. Small magnetic elements are arranged periodically on an elastic membrane to actuate a beam structure by an applied magnetic field. The arrangement pattern of elements changed the behavior of the present actuator. Finally we demonstrate a hand type actuator. The thumb of the hand-actuator can be deformed differently from the other four fingers even if the applied magnetic field is homogeneous. It is shown theoretically that the present actuator can work if it is miniaturized.

Gene transfer device utilizing micron-spiked electrodes produced by the self-organization phenomenon of Fe-alloy

In the diffusional phase transformation of two-phase alloys, the new phase precipitates form the matrix phase at specific temperatures, followed by the formation of a mixed microstructure comprising the precipitate and the matrix. It has been found that by specific chemical-etching treatment, the precipitate in Fe-25Cr-6Ni alloy projects substantially and clusters at the surface. The configuration of the precipitate has an extremely high aspect ratio: it is several microns in width and several tens of microns in length (known as micron-spiked). This study targets the development of a gene transfer device with a micro-spike produced based on the self-organization phenomenon of the Fe-25Cr-6Ni alloy. With this spike-projected device, we tried to efficiently transfer plasmid DNA into adherent cells by electric pulse-triggered gene transfer using a plasmid-loaded electrode (electroporation-based reverse transfection). The spiked structure was applied to a substrate of the device to allow efficient gene transfer into adherent cells, although the general substrate was flat and had a smooth surface. The results suggest that this unique spike-projected device has potential applications in gene transfer devices for the analysis of the human genome in the post-genome period.

Magnetic Micro Actuator Using Interactive Force between Magnetic Elements

In micro electro mechanical system (MEMS) field, there have been used many kinds of actuators. Among them, the magnetic actuator has some advantages. As magnetic micro actuators do not need electric wiring for energy supply, the structure can be simple and be downsized easily. However, the magnetic force would be very small with downsizing, which is the main problem for conventional magnetic actuators. We propose a new type actuator using magnetic interaction force between magnetic elements to solve this matter. This actuator can work even if it gets smaller, because the interaction force is dominant in a microscopic region. We fabricated the actuator by a casting process with photolithography using the SU-8 resist material. Then, the structure was fabricated by casting the mixture of poly(dimethylsiloxane) (PDMS) and a magnetic powder material. The beam type actuator works successfully and also shows interesting behavior. We can control the behavior of this actuator by changing the arrangement of magnetic elements on the structure. We also show theoretical evaluation of the deformation of the present actuator.

Effects of Resist Thickness and Viscoelasticity on the Cavity Filling Capability in Bilayer Thermal Embossing

Poly(methyl methacrylate) (PMMA) bilayer structures are employed as resists to investigate deformation of polymers by microthermal embossing. Owing to the dispersion of Fe3O4 particles in the upper layer, the distinct interface profiles of each layer resist can be observed by scanning electronic microscope (SEM). Deformation and replication fidelity are attributed to a variety of factors in the imprinting process. In particular, the thickness of each resist layer and the viscoelasticity of different molecular weight polymers play the most crucial roles among these factors. Based on experimental results, we improved the deformation models of imprinting for bilayer PMMA material and evaluated the models via specific parameters: the degree of deformation of the lower layer (DL), the fraction of cavity filling of the lower layer (FL), and variation in the fraction of the upper layer thickness (Ki). The final pattern of the upper or lower layer may be implicated in micro electro mechanical systems (MEMS).

Magneto-FEM analysis for micro actuator using array of magnetic elements

This paper reports a magnetic actuator using interaction between micro magnetic elements. It was already reported that the present actuator can work even if the structure was miniaturized to nano-scale. In the present work, simple fabrication process with photolithography and PDMS casting was employed to obtain beam type structures with micro array of magnetic elements on their surface. Two samples with simple grid patterns were prepared for testing. These samples had the same grid pattern but different orientation, which caused directly opposite bending deformation under the same applied magnetic field. We used magneto finite element method (FEM) to explain the behavior of the present actuators.

Laser Forming of Ti-6Al-7Nb Alloy Powder Compacts for Medical Devices

Titanium and its alloys have been widely used for medical and aerospace applications because of their excellent attributes of light metal, high strength, high corrosion resistance and high biocompatibility. Especially, Ti-6Al-7Nb alloy has been developed as a more suitable biomaterial to replace Ti-6Al-4V alloy, because vanadium is toxic element to the biological body. However, it is not easy to fabricate the complex shaped and precise parts by the conventional methods due to their poor castability and machinability. In this study, laser forming technique has been applied to solve the above problems. The precise structure was obtained by optimizing the laser forming parameters. Using this technique, a honeycomb structure was fabricated　effective to grow the neighboring tissue and also encourage osseointegration. Finally, mouse osteoblasts were cultured on the formed structures, resulted in the effectiveness of the honeycomb structure for biocompatibility.

Improvement of Solid Oxide Fuel Cell by imprinted patterns on eelectrolyte

This paper reports an improved interfacial structure between electrode and electrolyte of Solid Oxide Fuel Cell (SOFC). We employed an imprint process to give fine patterns onto a ceramic electrolyte sheet. The imprint process is a powerful tool to transcribe nano- to micro-patterns on materials. In the present work, a sheet of ceramic compound material was prepared, and micro patterns were given on the sheet. After debinding and sintering, dense ceramic sheet with fine patterns were obtained. We prepared three kinds of electrolyte sheets with different surface patterns using this technique. After applying anode and cathode layers, the three fuel cell samples were assembled to test the cell performance. It was resulted that the finer pattern caused the best performance in the three samples.

Evaluation and Analysis of Distortion of Complex Shaped Ti-6Al-4V Compacts by Metal Injection Molding Process

Titanium and its alloys have been widely used for medical and aerospace applications because of their excellent attributes of high specific strength, corrosion resistance, and biocompatibility. However, it is not easy to produce the complex shaped parts due to their poor castability and machinability. Metal injection molding (MIM) is one of suitable processing technique to produce the complex shaped parts in order to reduce the manufacturing cost. In this study, complex shaped Ti-6Al-4V compacts was prepared by MIM process for airplane application. The effects of high molecular binder content and different compact’s set-up during thermal debinding on the distortion of complex shaped compacts were measured and evaluated. The binder with 10 % APP (Atactic polypropylene) was found to have better shape retention for the parts. Furthermore the results indicate that high distortion occurs at early stage of thermal debinding process. The use of supports during thermal debinding can significantly reduce the distortion of the final parts.