Country：Japan

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Microelectronic Engineering  

Non-destructive testing methods based on magnetic Barkhausen noise (MBN) are expected to be applied to thin films. Recently, MBN analysis using machine learning has been performed on bulk materials and used as an in-situ stress and material evaluation method. However, for thin films, it is difficult to measure due to the weak MBN signal intensity, and few examples of its use as a stress and material evaluation method have been reported. This study acquired and analyzed MBN of Fe–Co polycrystalline thin films under bending stress. After pre-processing the acquired MBNs, two representative machine learning algorithms were used to learn the relationship between MBN and stress. By quantitatively comparing the prediction accuracy of each machine learning method, the characteristics of the MBN-based stress evaluation method were discussed from two perspectives: the need for domain knowledge and its applicability to unknown data. This study provides insight into machine learning-assisted MBN analysis as a stress evaluation method for thin films. The extension of MBN-based stress evaluation methods to thin films could be applied to the non-destructive stress evaluation of micro- and nanostructures, where stress state is critical, and could improve process development efficiency.

DOI： 10.1016/j.mee.2023.112057

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Other Link： https://www.sciencedirect.com/science/article/abs/pii/S0167931723001223

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.3390/nanomanufacturing3030020

Other Link： https://www.mdpi.com/2673-687X/3/3/20

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Magnetics Letters  

We present a novel manufacturing technique for generating unidirectional pores in ultraviolet (UV)-curable resins using self-assembled magnetic nanoparticles (MNPs) with chain-like structures. The method utilizes two templation mechanisms for pore formation: the UV-masking effect of the MNP chains and the physical presence of MNP chains themselves. Fe3O4 nanoparticles and PAK-01 were used as the template and UV-curable resin, respectively. Unidirectional pores formed only when resin/MNP mixtures were cured under a strong externally applied magnetic field. Water absorption tests indicated that some of the unidirectional pores were through-hole-type pores. The pores were cylindrical with an ellipsoidal cross-section. When the UV irradiation angle theta) was 30 degrees, the long and short diameters of the pores were approximately 9 and 8 mu m, respectively, before MNP removal, and 12 and 8 mu m, respectively, after removal. After MNP removal, the ellipticity of the pores in the samples increased from 1.5 to 2.4 with the increase in theta because of the increased UV-masking effect of the MNP chains.

DOI： 10.1109/LMAG.2023.3268851

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人 日本機械学会  

DOI： 10.1299/jsmemag.126.1253_38

CiNii Research

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

<p>As the application areas of MEMS (microelectromechanical systems) expand, more advanced functions and performance are being demanded from MEMS. To meet these demands, materials with various functionalities such as mechanical strength and shape memory, which are difficult to achieve with Si-based materials alone, are being used in MEMS. When applying new materials to MEMS, it is essential to establish micromachining techniques and control internal stresses in the same way as for Si-based thin films. In this research, a method for measuring the internal stress of thin film structures formed by microfabrication technology was developed. The thin film structure sample to be measured is in the form of a beam with fixed ends. The uniaxial strain due to internal stress is measured using a micro spring, and the internal stress is calculated. A process for fabricating a device that realizes the novel measurement method was devised and the device was fabricated. The microfabrication technique used was a reverse lift-off process, which can form thin film structures with rectangular cross-sections and uniform film thickness. Thin film metallic glass, an amorphous alloy with higher strength and lower Young's modulus than Si-based materials, was used as the new material to be measured. Using the developed measurement method, the internal stress change of the thin film was measured as a function of annealing temperature. As a result, it was confirmed that the internal stress of the thin film changed from the compressive direction to the tensile direction with increasing annealing temperature. The internal stress values measured by the novel method were compared with those measured by Stoney's equation, and the two measurement methods were close, demonstrating the usefulness of the new measurement method.</p>

DOI： 10.1299/mej.23-00074

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing Ltd  

In this study, we searched for Ti-Ni-Hf high formable shape memory alloys (HFSMAs) using combinatorial methods. By adding Hf to Ti-Ni SMAs, the potential is that Ti-Ni SMAs become metallic glasses. For efficient material search, the glass transition temperature was evaluated through combinatorial measurement of electrical resistance during crystallization. From the results, we searched for Ti-Ni-Hf HFSMAs, which undergo glass transition in the amorphous state. Ni-rich Ti-Ni-Hf thin-film amorphous alloys with more than 10 at% Hf content became thin film metallic glasses, whereas Ni-poor samples did not. Further, we evaluated the effect of annealing temperature on the martensitic transformation temperature of Ti-Ni-Hf SMAs using combinatorial methods. From the results, we measured the reverse transformation start temperature A (s) at 368-404 K, and it varied with the annealing temperature and Hf composition.

DOI： 10.35848/1347-4065/ac6a97

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing Ltd  

In this paper, the effect of structural relaxation at temperatures below crystallization on internal stress of Ni-Nb-Zr thin film amorphous alloy (including thin film metallic glass: TFMG) diaphragms was investigated. We fabiricated the Ni-Nb-Zr diaphragm samples with four compositions. Before fabrication of diaphragm structure by etching, Ni-Nb-Zr thin films on Si substrate were annealed at a temperature below crystallization (473, 523, and 573 K) for structural relaxation. By performing bulge tests on annealed Ni-Nb-Zr diaphragms, we were able to determine their mechanical properties. As the result, Young's modulus of all samples increased slightly with increasing annealing temperature because of the decrease of the free volumes during structural relaxation. Based on the results of internal stress, structural relaxation of all samples occurred below 473 K. Moreover, the effects of annealing temperature on internal stress differed by compositions. They were thought to be caused by the rate of structural relaxation. (C) 2022 The Japan Society of Applied Physics

DOI： 10.35848/1347-4065/ac5d12

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Magnetics  

Stress-driven magnetic Barkhausen noise (MBN) can be potentially used to develop a high-sensitivity dynamic force sensor. MBN is a compositional pulse due to the domain wall movement in ferromagnetic material induced by the external field. In this study, we provide an in-depth understanding of the responsiveness of MBN to external stress using ferromagnetic materials with a high magnetostriction constant ( $\lambda $ ). We demonstrate stress-driven MBN from strong textured Fe29Co71 alloy wires ( $\lambda _{\mathrm {s}} =117$ ppm)/epoxy resin composite via uniaxial compression testing by changing the stress rate level from 0.55 to 28 GPa/s under a static bias magnetic field of 55 mT. The relationship between the stress rate of the external force and root-mean-square (rms) value of MBN output voltages showed high sensitivity, i.e., $V_{\mathrm {rms}}= 0.00441 (d\sigma /dt)$ , and acceptable linearity that could be used to quantitatively evaluate the dynamic force. This stress-driven MBN generation mechanism could be based on the domain wall movement induced by the inverse magnetostrictive effect of FeCo alloys. We believe that this study will aid in the research focusing on the dynamic magnetostrictive mechanism and development of novel applications for high-sensitivity force sensors that have no batteries.

DOI： 10.1109/TMAG.2021.3126898

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASME  

Catheter surgery is a minimally invasive treatment in which visual information is limited to a two-dimensional image generated by an X-ray camera. This results in the possibility that stress applied by the catheter onto a blood vessel wall damages the vessel. Doctors must therefore be skillful at catheter surgery. We proposed a catheter surgery simulator that visualizes the stress applied to the blood vessel wall using photoelasticity. The manufacture of this simulator requires creating blood vessel mimics that reproduce the physical properties of blood vessel tissue using photoelasticity. This study investigated the mechanical and photoelastic properties of gel materials and selected a gel composition suitable for making blood vessel mimics. The mechanical properties of polyvinyl alcohol (PVA) hydrogel changed in the range 70-335 kPa by changing the composition ratio, and double network (DN) gel changed in the range 0.13-1.06 MPa by changing the composition ratio. These gels could be adjusted by changing the material composition to provide Young's moduli similar to that of blood vessels. The photoelastic properties of PVA hydrogel changed in the range 1.38-2.76 x 10(-9)/Pa by changing the composition ratio, and DN gel changed in the range 0.012-0.029 x 10(-9)/Pa by changing the composition ratio.

DOI： 10.1115/1.4051516

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

<p>In this paper, we report on the fabrication and evaluation of actuator for reaction force variable passive-type tactile display using high formable Ti-Ni-Cu shape memory alloy. This actuator is driven by the superelastic effect and superior in force expression, responsiveness, and miniaturization compared to conventional tactile displays using shape memory alloys. This actuator was fabricated in a convex shape by utilizing a viscous flow of Ti-Ni-Cu metallic glass. After crystallization, the metallic glass was changed to the shape memory alloy. In this manner, we successfully acquired the desired convex cross structure with a height of 123 µm at the center of cross. Additionally, while pushing 100 µm, we successfully varied the reaction force ranged from 40 to 80 mN, necessary to deform the skin and electrical resistance linearly by controlling the temperature. From these results, we showed that the actuator of this study can be used as tactile display that can express desired hardness and softness by temperature control. We also showed the possibility that the temperature of each actuator can be controlled individually by electrical heating using the linear relationship between temperature and electrical resistance.</p>

DOI： 10.1541/ieejsmas.141.304

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CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

Fe-based nanocrystalline FeSiBPCuC alloys (NANOMET (R)) with a combination of high magnetic flux density, high permeability, and low iron loss have attracted much attention for use in magnetic core devices such as small power supplies, motors, and transformers. However, further improvement of the corrosion resistance is still required because surface oxidation during the water atomization process inevitably deteriorates the magnetic properties of these alloys. Here, we use a combinatorial magnetron sputtering system to fabricate new (FeSiBPCuC)100xyNix(Nb,Mo)y (0 < x < 10, 0 < y < 2 at%) amorphous thin films with enhanced corrosion resistance. We found that the co-presence of Ni (2-4 at%) and Mo (1-2 at%) in the FeSiBPCuC amorphous thin films promoted a further improvement of the corrosion resistance. The magnetic coercivity of (FeSiBPCuC)95.5Ni4.0Nb0.5 and (FeSiBPCuC)97.0Ni2.0Mo1.0 thin films was deteriorated compared with that of a FeSiBPCuC ribbon.

DOI： 10.1016/j.jnoncrysol.2021.120808

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Ar plasma in a fast atom beam (FAB) source with magnetic fields, which was previously developed [Precis. Eng. 62, 106 (2020)] to achieve high-performance surface activated bonding, was analyzed by particle-in-cell-Monte Carlo collision simulation and experimental measurements. Simulation in the proposed FAB source with magnetic fields shows that higher electron density accumulation occurs near the irradiation port by E x B drift, and the potential gradient near the irradiation port steepens, which results in an increase in Ar+ flux to the irradiation port. The variation in the plasma distribution due to the effect of the magnetic field contributes to an increase in the amount of Ar-FAB irradiation, which reduces erosion of the carbon electrodes and suppresses the formation of carbon agglomerates. These simulation results were verified experimentally with Langmuir probe measurements and FAB irradiation experiments with oxide layer removal. The analysis results explain why high performance is achieved with the proposed FAB source.

DOI： 10.35848/1347-4065/abe683

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we report the fabrication and evaluation of an actuator for reaction force variable passive-type tactile displays using a highly formable Ti-Ni-Cu shape-memory alloy. The actuator relies on the superelastic effect of SMAs and can influence the applied reaction force. We successfully fabricated the desired convex cross structure with a height of 123 mu m, varied the reaction force between 40 and 80 mN at a depth of 100 mu m, and controlled the electrical resistance linearly with temperature.

DOI： 10.1109/TRANSDUCERS50396.2021.9495608

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2021 7th International Workshop on Low Temperature Bonding for 3D Integration, LTB-3D 2021  

We clarify a mechanism for longer lifetime of the fast atom beam (FAB) source for surface activated bonding proposed in our previous study. The new FAB source achieves highly efficient FAB irradiation and suppression of generation of fine carbon (C) particles. In this study, the distribution of sputtering and deposition on the inner wall of the C electrodes have been evaluated by measuring the thickness of the electrodes before and after long-time use. In the new source, the C erosion area due to sputtering is localized near the irradiation port and the sputtered C is deposited on other electrode surface, whereas in the conventional one, the erosion occurs on all surfaces of C electrodes. The reduction of electrode erosion due to sputtering contributes significantly to the extension of the lifetime of the new FAB source.

DOI： 10.1109/LTB-3D53950.2021.9598414

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In this research, we aimed to establish a new measurement method of internal stress using MEMS structures. The measurement sample was a thin film metallic glass, which has higher strength and lower Young's modulus compared to Poly-Si. The thin film metallic glass samples were formed by sputtering, and their shape was a fixed beam at both ends. In order to avoid the deterioration of the cross-sectional shape of the structure caused by the film thickening, we used a reverse lift-off method. It is the method that forms film on a desired pattern and remove the others to obtain the flat and uniform thickness structure. We devised a process to fabricate devices to measure the internal stress of a thin film metallic glass samples and confirmed the feasibility of fabricating the devices by carrying out the process. We also tried to measure the displacement of the devices that were successfully fabricated devices.</p>

DOI： 10.1299/jsmemecj.2021.j221-07

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In this paper, it is reviewed that combinatorial technologies for the fabrication and characterization of a large number of samples at once, the use of MEMS and other microfabrication technologies for the characterization of the samples, and our efforts to use machine learning to analyze and improve the search efficiency of the large number of sample data obtained by the combinatorial technologies. We introduce combinatorial arc plasma deposition, which enables the combinatorial deposition of amorphous alloy materials. The composition-graded films fabricated by this method are separated and labeled into thin-film libraries by using microfabrication methods, and their properties are evaluated using MEMS structures. As an example of material search with the aid of machine learning, we describe the identification of physical properties with high contribution to the current density of electrocatalysts by random forest analysis, the examination of search termination conditions by Bayesian optimization, and the estimation of crystal grain size of magnetic materials from Barkhausen noise by machine learning.</p>

DOI： 10.1299/jsmemecj.2021.k041-01

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

© 2019 Elsevier Inc. Surface-activated bonding (SAB), also called room-temperature bonding, is used in three-dimensional integration technology for semiconductor devices. An Ar fast atom beam (FAB) is used for SAB. However, conventional FAB guns must be replaced after hundreds of minutes of irradiation because carbon abrasion powders are generated by Ar ions sputtering in the gun. Therefore, this study develops a novel FAB gun with improved lifetime. The proposed FAB gun applies magnetic fields to guide Ar ions to reduce sputtering in the gun and improve irradiation efficiency. The proposed FAB gun indicates the possibility of improving gun lifetime.

DOI： 10.1016/j.precisioneng.2019.11.006

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Publisher：JSME 2020 Conference on Leading Edge Manufacturing/Materials and Processing, LEMP 2020  

The present paper proposes novel microvalves remotely controlled without electrical wiring on each valve. The proposed microvalves are controlled utilizing heat from magnetic nanoparticles in an alternating magnetic field. A procedure for fabrication of the microvalves was established. the fabricated microvalves operated on a hotplate.

DOI： 10.1115/LEMP2020-8529

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmemp.2020.28.267

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmemp.2020.28.266

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>We reported on the fabrication of tactile pins for reaction force variable passive type tactile displays using Ti-Ni-Cu high formable shape memory alloys. These devices take advantage of the temperature controllability of the resilience of the superelasticity effect and present hardness and softness tactile sensation. After the tactile pins being formed into three-dimensional shape by viscous flow of metallic glasses, they became shape memory alloys by annealing for crystallization. The height of tactile pin formed by conventional method was about 110 μm. However, when tactile pin was pushed by the finger, it was insufficient deformation for the stable superelasticity effect to appear. Therefore, we attempted to increase the height of tactile pin by the improving deformation method using rapidly temperature raising during forming for decreasing viscosity of metallic glasses. As a result, we successfully increased the height of tactile pin to 237 μm.</p>

DOI： 10.1299/jsmemecj.2020.j22210

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In this paper, we fabricated three types of optical textured glass substrates by a polydimethylsiloxane (PDMS) nanoimprint lithography (NIL) on the front glass to enhance conversion efficiency of dye-sensitized solar cells (DSSCs). Three types of master molds for micro-texture (M-Tx), nano-texture (N-Tx), and micro-nano-double texture (D-Tx) were prepared by an aluminum anodic oxidation. Finally, we fabricated DSSCs with textured glass. The used dye was red N719. The cell size was 6 mm square. As the results, the conversion efficiency of DSSCs with textured glasses increased by 7.5% for M-Tx (<i>η</i> of 2.74%), 18% for N-Tx (<i>η</i> of 3.01%) and 26% for D-Tx (<i>η</i> of 3.22%) compared to DSSC with flat glass (<i>η</i> of 2.55%).</p>

DOI： 10.1299/jsmemecj.2020.j22207

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmemp.2020.28.158

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>Most microvalves need electrical wiring on each one, and the need will disturb further integration and miniaturization of microfluidic systems soon. The present study proposes new remotely controlled microvalves without the electrical wiring on each valve. The microvalves consist of thermo-responsive gels and magnetic nanoparticles, and they run with heat dissipation from the magnetic nanoparticles in an alternating magnetic field. The microvalves open via shrinking of the thermo-responsive gels through the heat dissipation. In this paper, the microvalves were fabricated using Fe₃O₄ nanoparticles and patternable thermo-responsive gels mainly made from poly(<i>N</i>-isopropyl acrylamide) (PNIPA). The gels incorporating the magnetic nanoparticles were installed in Poly(dimethylsiloxane) (PDMS) microchannels. The microchannels were fabricated using a mold made of SU-8. The fabricated microvalve could perfectly block the flow of water under conditions without any external magnetic fields. When the closing microvalve was exposed to an alternating magnetic field (2 MHz, 50 Oe), the microvalve was opened and the water flow was observed. When the alternating magnetic field was stopped, the microvalve was closed again and the water flow was stopped. The proposed microvalves were successfully fabricated, and the microvalves could be operated by the alternating magnetic field as expected.</p>

DOI： 10.1299/jsmemecj.2020.j22204

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In recent years, minimally invasive treatment has attracted attention, and catheter surgery is one of them. On the other hand, there is a problem that stress is applied to the blood vessel wall and it is damaged, so doctors are required the skill of catheter surgery. In order to improve the skill of catheter surgery, the authors have proposed a surgical simulator that realizes real-time visualization of stress by the photoelasticity. Photoelasticity is a property in which an isotropic elastic body such as glass or acrylic that receives an external force causes birefringence. It is often used as an experimental method to analyze the stress distribution of materials. In this study, it is proposed a measurement system for surgical simulator that can measure three-dimensional stress. The shape of the blood vessel model applicable to the proposed measurement system is determined and introduce a stress correction that guarantees constant accuracy. Finally, it is showed that the stress can be visualized in real time.</p>

DOI： 10.1299/jsmemecj.2020.j24111

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>This study creates a blood vessel model for a catheter surgery simulator. In previous study was succeeded in producing a blood vessel model applicable to a surgical simulator using PVA hydrogel. On the other hand, the problem with the blood vessel model is that the reproducibility of the mechanical properties of blood vessels, which is important for the actual catheter operation sensation, is low. Therefore, in this study, creates a blood vessel model with a two-layer structure that reproduces the mechanical properties of the blood vessel wall and adipose tissue. In the proposed blood vessel model, it is shown that the mechanical properties can be reproduced by changing the compounding ratio of powdered PVA and the mass ratio of water and DMSO as a solvent. Furthermore, this study proposes a method for producing a two-layer structure and show that it is possible to produce a blood vessel model with a two-layer structure.</p>

DOI： 10.1299/jsmemp.2020.28.156

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>The novel fast atom beam source (FAB) for surface-activated bonding (SAB) method was proposed in order to improve the lifetime of FAB sources. The proposed FAB source achieved the higher efficiency of Ar-FAB irradiation and less wear on the electrodes. This previously study indicated that the applied magnetic fields made the Ar ions converge on the irradiation port, increasing Ar irradiation efficiency. However, it was not measured and not clearly why the proposed FAB source achieved higher performance. In this study, we aim to reveal the factor of achievement high performance and to propose the new structure of the FAB source with much higher performance by plasma analysis. Electrostatic probe studies and the simulation for Ar plasma in the proposed source show that the electron and Ar⁺ density increase near the irradiation port. Moreover, increasing Ar⁺ flux only to the wall with irradiation port indicates improving Ar-FAB irradiation efficiency and suppressing Ar+ sputtering and carbon agglomerates on inside wall of the source.</p>

DOI： 10.1299/jsmemecj.2020.j13105

CiNii Research

Publisher：MHS 2019 - 30th 2019 International Symposium on Micro-NanoMechatronics and Human Science  

In this paper, we fabricated optical textured glass substrates by a polydimethylsiloxane (PDMS) nanoimprint lithography (NIL) on the front glass to enhance conversion efficiency of dye-sensitized solar cells (DSSCs). Two types of nano-texture (N-Tx) and micro-nano-double texture (D-Tx) were prepared. Finally, we fabricated DSSCs with textured glass. The used dye was red N719. The cell size was 6 mm square. As the results, the conversion efficiency of DSSCs with textured glasses increased by 26% for N-Tx and 19% for D-Tx compared to DSSC with flat glass.

DOI： 10.1109/MHS48134.2019.9249295

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Publisher：MHS 2019 - 30th 2019 International Symposium on Micro-NanoMechatronics and Human Science  

Most microvalves need electrical wiring on each one, and the need prevents further integration and miniaturization of microfluidic systems. Hence, we propose novel microvalves remotely controlled without the wiring on each valve. The proposed microvalves are driven by heat from magnetic nanoparticles in an alternating magnetic field. The nano-scale magnetic particles, which possess superparamagnetic behavior, generate heat in the alternating magnetic field. There is a theoretical formula for the heat generation. However, few reports are available on comparing experimental values of the heat generation with theoretical values. In this study, the experimental heating power was compared with the theoretical values, and the possibility of the proposed microvalves was verified.

DOI： 10.1109/MHS48134.2019.9249321

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Publisher：MHS 2019 - 30th 2019 International Symposium on Micro-NanoMechatronics and Human Science  

In recent years, minimally invasive treatment aimed at reducing the physical and mental burden of patients as well as treating diseases has attracted attention. Catheter surgery is one of the minimally invasive treatments. This surgical technique can reduce invasion compared to incision and replacement with artificial vessels. Furthermore, it is known to be superior in terms of safety. On the other hand, in catheter surgery, visual information is limited to only a two-dimensional image by an X-ray camera. Therefore, there is a problem that stress is applied to the blood vessel wall and it is damaged, so doctors are required the skill of catheter surgery. This study is proposed a catheter surgery simulator that visualizes the stress applied to the blood vessel wall in realtime using photoelasticity. The blood vessel model used for the surgery simulator focused on PVA hydrogel. Previous experiments by our group have shown that PVA hydrogel can be applied to a surgical simulator. This study has developed an image processing program to measure stress in real-time. It has verified that the application to a surgery simulator is possible by this image processing program.

DOI： 10.1109/MHS48134.2019.9249277

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Publisher：MHS 2019 - 30th 2019 International Symposium on Micro-NanoMechatronics and Human Science  

Dynamic force sensors play a key role in emerging smart technologies that can measure various types of human motions. Magnetostrictive force sensors are the most promising, lightweight, and reliable sensing technologies; however, an in-depth understanding of the sensing mechanism is still lacking. In this study, we focus on magnetic Barkhausen noise (MBN), which is generated by the inverse magnetostriction effect upon impact loading. Further, the stress-induced MBN characteristics of Fe-Co alloy/epoxy composites were investigated using a cyclic compression test. By measuring and analyzing MBN signals in magnetostrictive/epoxy resin composites, it was revealed that the root mean square value of MBN increased linearly with the increase in the stress rate. Additionally, we observed that the MBN outbreaks were affected by the magnetostriction constant. The proposed MBN force sensor system is expected to achieve high sensitivity, wide measurement range, and downsizing.

DOI： 10.1109/MHS48134.2019.9249081

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Language：English   Publisher：FRONTIERS MEDIA SA  

© 2019 THOSS Media &amp; De Gruyter, Berlin/Boston. We proposed a fabrication of nanoimprinted textures on a front glass/transparent conductive oxide interface for dye-sensitized solar cells (DSSCs). These textures were fabricated through polydimethylsiloxane (PDMS) nanoimprint lithography on organosilsesquioxane solution. The texture structures were estimated via optical simulation. Master molds were anodic aluminum oxide templates with nano-texture (N-Tx) and micro-nano double texture (D-Tx). Meanwhile, replicate molds used a hard PDMS. Fluorine-doped tin oxide and titanium dioxide were deposited on textured glass substrates to generate electrodes for DSSCs. Unlike the DSSCs without texture, textured DSSCs realized 11.4% (N-Tx) and 10% (D-Tx) improvement in conversion efficiency.

DOI： 10.1515/aot-2019-0010

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Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>本研究では，サンプルとして，ガラス基板上に長さ4 mm，幅1 mm，厚さ500 nmの薄膜金属ガラスPd₇₇Cu₇Si₁₆ at.%を10 mm間隔に成膜し，試作した温度傾斜加熱装置により，543 K以下，471 K以上の異なる温度で同時加熱試験を行った．この時の各温度での大気中における結晶化度の時間変化を，放射率変化としてサーモグラフィで捉えることに成功し，XRDにより結晶化度を測定した．</p>

DOI： 10.11522/pscjspe.2019a.0_5

CiNii Research

Language：Japanese   Publisher：公益社団法人 精密工学会  

<p>表面活性化接合は半導体分野における三次元積層技術として利用されている．しかし，表面活性化接合に用いられる高速原子ビームガンは，短時間の使用で内部が磨耗してしまう．そこで，高速原子ビームの高効率な照射により，接合回数に対する相対的な長寿命化を目指す新規高速原子ビームガンの開発を行った．また，新規高速原子ビームガンを用いて，その照射特性を評価し，更なる高性能化を目指した設計指針の確立を目指した．</p>

DOI： 10.11522/pscjspe.2019a.0_687

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electrical Engineers of Japan  

<p>Nonspherical monodisperse polydimethylsiloxane (PDMS) microparticles were fabricated by lithography and ultraviolet ozone (UVO) treatment for self-assembly of periodic structures. PDMS solution was poured into photoresist molds on glass substrates, whereupon it was cured at 80°C. After irradiating ultraviolet to the surface of the PDMS, remaining thin PDMS films on the molds were eliminated using ultrasonic waves. Attenuated-total-reflection Fourier-transform infrared spectra indicated that the surface of the UVO treated PDMS was changed to glass SiO₂-like materials, resulting that the remaining thin PDMS films could be ultrasonically removed by fracture. The PDMS microparticles were separated from the substrates using ultrasonic waves, and microparticles of a desired shaped were formed. A suspension was prepared by mixing the PDMS microparticles in deionized water, and a droplet of the suspension was placed on a hydrophobic template substrate. The PDMS microparticles self-assembled on the substrate along the template walls, leading to PDMS microparticles being closely packed. Such PDMS microfabrication would be useful for microdevices.</p>

DOI： 10.1541/ieejsmas.139.132

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Language：English   Publishing type：Research paper (scientific journal)  

© 1992-2012 IEEE. Based on our prior combinatorial analysis aimed at materials discovery, Cu82Cr18 and Cu80Cr20 were selected in chemical dealloying experiments as candidates for incorporation in sensors for the first time. The Cu82Cr18 film was Cu-dealloyed, altering its composition to Cu25Cr75 after 7 min of dealloying. The dealloyed Cu82Cr18 film exhibited a Cr-based nanoporous structure with 20-40-nm-diameter pores, indicating that Cu was sufficiently dealloyed. In contrast, the Cu80Cr20 film could not be sufficiently Cu-dealloyed, which was consistent with the results of the combinatorial analysis; the original composition was changed to Cu46Cr54 after 7 min, and the pores were not visible. Sensors A and B were fabricated via chemical dealloying of Cu82Cr18 and Cu80Cr20, respectively, and they were evaluated with respect to a reference sensor in both air and oil. The measured hysteresis in the air was 7.4% full scale (FS) for sensor A, which was below the acceptable limit of 10.0% FS, whereas that for sensor B was 13.3% FS. Moreover, the 90% response time in oil was 8 min for sensor A and 10 min for sensor B, as compared to 12 min for the reference sensor; thus, the response time of sensor A was below the acceptable limit of 10 min. [2018-0242]

DOI： 10.1109/JMEMS.2019.2895164

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DOI： 10.1128/MRA.01441-18

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Language：English   Publisher：IEEE  

© 2019 IEEE. We report on the fabrication and evaluation of tactile pins for passive-type tactile displays using high formable Ti-Ni-Cu shape memory alloy. These pins were fabricated by utilizing a viscous flow of Ti-Ni-Cu metallic glass. After crystallization, the material transformed to a shape memory alloy and was driven by the superelastic effect. In this manner, we successfully acquired the desired three-dimensional structure and measured a reaction force of 20 mN or larger, necessary to deform the skin. Additionally, we successfully varied the reaction force by controlling the temperature and demonstrated the potential application of these tactile pins.

DOI： 10.1109/transducers.2019.8808618

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In this study, we propose a combinatorial evaluation method for evaluating the corrosion resistance of the Ti-Ni-based high formable shape memory alloys (HFSMAs) based on anodic polarization tests. The proposed evaluation substrates compose nine samples which have different compositions. These samples are deposited on a glass substrate by carousel sputtering system and microelectromechanical processes. Further, we performed anodic polarization tests on the Ti–Ni–Zr and Ti–Ni–Cu HFSMAs samples. The polarization curves are obtained by sweeping the potential and the current density at the passive state (<i>i</i>_ps) of each composition tested is compared. In case of the Ti–Ni–Zr alloy, <i>i</i>_ps varied depending on the Zr content. When the Zr content ranged from 10 to 15 at.%, their <i>i</i>_ps were comparable with that of Ti₄₈Ni₅₂ used in medical devices. On the other hand, in case of the Ti-Ni-Cu alloy, their <i>i</i>_ps were similar to that of Ti₄₈Ni₅₂ regardless of Cu content. We obtained Ti–Ni–Zr and Ti–Ni–Cu HFSMAs having a corrosion resistance equivalent to that of Ti₄₈Ni₅₂. Furthermore, we conducted XPS analysis to investigate the passive film of HFSMAs. The thin surface film of Ti-Ni-Zr alloys were composed of TiO₂ and ZrO₂, while that of Ti-Ni-Cu alloys were composed of only TiO₂. We have concluded that the formation of TiO₂ enriched protective thin surface film might have been responsible for the high corrosion resistance.</p>

DOI： 10.1299/jsmemp.2019.27.207

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In this paper, we fabricated two types of optical textured glass substrates by a polydimethylsiloxane (PDMS) nanoimprint lithography (NIL) on the front glass to enhance conversion efficiency of dye-sensitized solar cells (DSSCs). Two types of master molds for nano-texture (N-Tx) and micro-nano-double texture (D-Tx) were prepared by an aluminum anodic oxidation. Both N-Tx and D-Tx showed higher total transmittance and lower reflectance than bare glass. Finally, we fabricated DSSCs with textured glass. The used dye was red N719. The cell size was 6 mm square. As the results, the conversion efficiency of DSSCs with textured glasses increased by 26% for N-Tx (<i>η</i> of 3.67%) and 19% for D-Tx (<i>η</i> of 3.47%) compared to DSSC with flat glass (<i>η</i> of 2.91%).</p>

DOI： 10.1299/jsmemp.2019.27.p04

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>MEMS mirror device is a device that reflects and scans a laser by the torsion of the beam structure. By miniaturization of the device, the reduction of the deflection angle of the mirror becomes to be an issue. In this research, we fabricated a MEMS mirror structure using film metallic glass formed by sputtering as a new material for the beam structure. In order to avoid the deterioration of the cross-sectional shape of the structure caused by the film thickening, a reverse lift-off method was used in the fabrication process. It is the method that forms film on a desired pattern and remove the others to obtain the flat and uniform thickness structure. Several conditions of the anneal was tested and the structure annealed at 200 ℃ shows less deflection than others. The fabricated structure was driven by external excitation, and it was confirmed that the resonance frequency was almost as designed.</p>

DOI： 10.1299/jsmemecj.2019.j22208p

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In recent years, minimally invasive treatment has attracted attention, and catheter surgery is one of them. On the other hand, in catheter surgery, visual information is limited to only a two-dimensional image by an X-ray camera. Therefore, there is a problem that stress is applied to the blood vessel wall and it is damaged, so doctors are required the skill of catheter surgery. In order to improve the surgeon's surgical technique, the authors have proposed a surgical simulator that realizes real-time visualization of stress by the photoelastic method. In this study, we propose a measurement system using a photoelastic method that can visualize stress in three dimensions and examine the blood vessel model shape applicable to the proposed measurement system.</p>

DOI： 10.1299/jsmemp.2019.27.p01

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Direct laser-writing techniques have attracted attention for their use in two- and three-dimensional printing technologies. In this article, we report on a micropatterning process that uses femtosecond laser reductive sintering of mixed CuO/NiO nanoparticles. The writing speed, laser fluence, and incident total energy were varied to investigate the influence of heat accumulation on the micropatterns formed by these materials. Heat accumulation and the thermal history of the laser irradiation process significantly affected the material composition and the thermoelectric properties of the fabricated micropatterns. Short laser irradiation durations and high laser fluences decrease the amount of metal oxide in the micropatterns. Selective fabrication of p-type and n-type thermoelectric micropatterns was demonstrated to be possible with control of the reduction and reoxidization reactions through the control of writing speed and total irradiation energy.

DOI： 10.3390/mi9060264

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Publisher：Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)  

In this study, novel transparent nanoporous films exhibiting insulating properties were fabricated by a new chemical dealloying method of Cu-Cr with no requirement of high-temperature annealing. Furthermore, for the first time to the best of our knowledge, the fabricated nanoporous film was successfully applied as a nanoporous electrode film filter of a moisture-in-oil sensor: The fabricated moisture-in-oil sensor exhibited outstanding sensitivity and a low hysteresis of 7.4% FS in air, which was less than the desired value of 10.0% FS. Furthermore, the sensor exhibited a favorable 90% response time in oil, which was 8 min and well less than the desired value of 10 min.

DOI： 10.1109/MEMSYS.2018.8346753

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Verlag  

p-type and n-type thermoelectric micropatterns were selectively fabricated via the reduction and reoxidation of CuO/NiO mixed nanoparticles using femtosecond laser pulses. The micropatterns were formed by raster scanning focused femtosecond laser pulses on a solution film containing CuO and NiO nanoparticles, ethylene glycol, and polyvinylpyrrolidone, followed by the removal of the non-irradiated nanoparticles. Cu–Ni was generated by reductive sintering of the CuO/NiO mixed nanoparticles at laser scanning speeds ranging from 5 to 20 mm/s and a laser fluence of 0.055 J/cm2. In contrast, intense peaks corresponding to Cu2O and NiO were observed in the X-ray diffraction spectrum of the micropattern formed at a scanning speed of 1 mm/s, indicating that Cu2O and NiO were generated via the reoxidation of the reduced metals. The Seebeck coefficients of the micropatterns formed at a fluence of 0.055 J/cm2 and scanning speeds of 5–20 mm/s were between − 32 and − 16 µV/K, whereas that of the micropattern formed at a fluence of 0.055 J/cm2 and scanning speed of 1 mm/s was ~ 250 µV/K. These results suggest that the Seebeck coefficient depends on the generated n-type Cu–Ni and p-type Cu2O and NiO phases. A thermoelectric couple was fabricated by selectively fabricating p-type and n-type thermoelectric elements. The thermoelectric couple exhibited a thermoelectric voltage of 0.25 mV/K when a temperature gradient was applied between its hot and cold sides. The generated voltage was nearly consistent with the estimated voltage based on the Seebeck coefficient. The developed process for selective fabrication is expected to be useful for the direct writing of thermoelectric-type sensors.

DOI： 10.1007/s00339-017-1489-x

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1557/adv.2018.198

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Language：English   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

© Copyright SPIE. Cu-based fine patterns were directly fabricated using femtosecond laser reduction of Cu2O nanospheres (NSs) via nonlinear optical absorption. Cu2O NS solution films, containing Cu2O NSs, polyvinylpyrrolidone (PVP), and 2-propanol, were prepared by spin-coating of the Cu2O NS solution on glass substrates or Cu-coated glass substrates. Finer line patterns were formed by scanning the focused femtosecond laser pulses. The absorption of the Cu2O NS solution film at wavelength of the femtosecond laser pulses, 780 nm, was low, whereas the intense absorption at wavelength of 390 nm was observed. Finer patterns were obtained on the Cu-coated glass substrates than on the glass substrates. The minimum line width of 0.6 μm was obtained on the Cu-sputtered film, which was smaller than the focal spot diameter of 1.3 μm. The heat accumulation is lower on the Cu-sputtered films due to their high thermal conductivity, resulting that the line width with the sub diffraction limit was achieved. The electrical conductivity of the patterns on the glass substrates was evaluated to be 4.1×106S/m at scanning speed of 200 μm/s and pulse energy of 0.312 nJ, which is close to that of bulk copper.

DOI： 10.1117/12.2287686

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DOI： 10.1088/1742-6596/1052/1/012032

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

2D and 3D metal microstructures are directly written using femtosecond laser reductive sintering of metal oxide nanoparticles. CuO nanoparticle solutions including CuO nanoparticles, a reductant agent, and a dispersant, were coated on glass substrates. Then, focused femtosecond laser pulses were irradiated onto the solution film to write the microstructures in air. Finally, non-irradiated CuO nanoparticles were removed. Cu-rich and Cu2O-rich microstructures were selectively fabricated by controlling the laser irradiation conditions. We demonstrated direct-writing of 2D and 3D Cu-based microstructures using femtosecond laser-induced reduction of CuO NPs. Using respective appropriate femtosecond laser conditions, 3D Cu-rich microstructures were obtained by a combined process of the dispensing coating and laser irradiation. The Cu-rich hot-film flow sensor which had microbridge structure, were successfully produced. This direct-writing technique is useful for fabricating various sensors on arbitral shaped substrates in air.

DOI： 10.1117/12.2290166

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Language：Japanese   Publisher：The Laser Society of Japan  

2D and 3D metal microstructures were directly written using the femtosecond laser reductive sintering
of metal oxide nanoparticles. We coated CuO nanoparticle solutions, including CuO nanoparticles, a
reductant agent, and a dispersant, on glass substrates. Then the focused femtosecond laser pulses were
irradiated onto the solution film to write the microstructures in air. Finally, the non-irradiated CuO
nanoparticles were removed. Cu-rich and Cu2O-rich microstructures were selectively fabricated by
controlling the laser irradiation conditions. We applied this process to the fabrication of 2D Cu/Cu2O
microtemperature sensors and 3D Cu-rich micro flow sensors. We believe this process is useful for
fabricating various sensors on arbitral shaped substrates in air.

DOI： 10.2184/lsj.46.5_257

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmetokai.2018.67.208

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmemp.2018.26.901

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>Ti-Ni-Cu high formable shape memory alloys (HFSMAs) show the characteristics of thin film metallic glasses (TFMGs) when the as-sputtered deposited samples and show the characteristics of the shape memory alloys after crystallization. Conventional Ti-Ni based SMAs show poor workability. On the other hand, the HFSMAs show excellent workability by utilizing the viscous flow in the supercooled liquid region (SCLR). In this study, we demonstrated to fabricate HFSMAs foldable tube structures for the medical application such as the stent or the sheath portion of the forceps. The Ti49Ni41Cu10 (at.%) TFMG samples were fabricated by a r.f. magnetron sputtering system. The Ti49Ni41Cu10 HFSMAs crystallized at 773 K-3.6ks exhibited a martensitic transformation temperature near body temperature. We fabricated the foldable tube shape by the following processes. Ti49Ni41Cu10 TFMG flat samples were deformed into wave shape by jig in the SCLR. And then, waved samples were also deformed into circular shape by viscous flow. For produce of tube shape, each edge of wave samples was also bonded at 623 K and 648 K by viscous flow. Finally, a foldable tube shape was annealed at 773 K for 3.6 ks, and then we obtained SMA foldable tube shapes. These tube showed shape memory effect and superelastic properties.</p>

DOI： 10.1299/jsmemecj.2018.j2220202

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmetokai.2018.67.224

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmetokai.2018.67.223

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>Tactile display is the device that show information by stimulate person’s skin. Characteristics of shape memory alloys (SMA) is large deformation and high generative force, so it is one of the microactuators used in tactile display. Conventional tactile display using SMAs are complex structures because SMAs need bias force for actuation. In this paper, we proposed novel driving parts of tactile display using high-formable shape memory alloys (HF-SMAs). Since HF-SMAs have characteristics of the metallic glasses when it is as-deposited, 3D structures of HF-SMAs are formed in the supercooled liquid region. Therefore, we can get 3D structure that is integrated type of driving part and tactile pin for tactile display by using HF-SMAs. We reported fabrication process of driving part and tactile pin.</p>

DOI： 10.1299/jsmemecj.2018.j2220305

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmetokai.2018.67.703

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In this study, we proposed combinatorial evaluation methods for biocompatibility of high formable shape memory alloys (HFSMAs) by anodic polarization tests, which is one of biocompatibility evaluation indicators. Evaluation substrates for evaluating anodic polarization characteristics were designed and fabricated, validity of proposed evaluation substrates was confirmed. The evaluation substrate was fabricated by micro electro mechanical systems (MEMS) processes. 9 Ti-Ni-Zr samples which have same composition were prepared on the glass substrate by a r.f. magnetron sputtering system. We evaluated anodic polarization characteristics of HFSMA using proposed evaluation substrates. In the anodic polarization tests, the evaluation substrate was immersed in physiological saline (NaCl solution of 9 g/L) at 37°C, the polarization curves were obtained by sweeping the potential. The results of the polarization curves of each sample were compared and the variation of data was investigated. As the results, the standard deviation from the average value of the passivation potential (<i>P</i>_crt) was about 2 %, and the polarization curves showed the same tendency. We concluded that the validity of proposed evaluation substrate was confirmed.</p>

DOI： 10.1299/jsmemecj.2018.j2220201

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>We proposed fabrication process of optical substrates for dye sensitized solar cells (DSSCs) by a solvent-assisted room temperature nanoimprint. Textures were fabricated at front glass/Transparent Conductive Oxide (TCO) interface. Light absorptance will improve due to inner Anti Reflection (AR) effect and light path length will increase due to scattering, both benefiting conversion efficiency. Moreover, as structures appeared at TiO₂ interface enlarge surface area, shorter dye adsorption time can be realized. Three master molds (with nano, micro, and micro-nano double structures) were fabricated by anodization and wet etching. PDMS molds were replicated from master molds. Using PDMS replica molds, textures were transformed onto glass substrate by nanoimprint. Aluminum doped Zinc Oxide (AZO) was deposited on the textured substrates by a RF sputtering system. Optical and electrical properties were evaluated by an UV/VIS/NIR spectrophotometer with integrating sphere system and a low resistivity meter. Textured substrates showed high diffuse transmittance, indicating larger scattering inside TCO films. Inner AR effect evaluation will be executed in further research after TiO₂ application. As for resistivity, substrates with micro and double structures showed better property. In future, we will fabricate DSSCs using the optical substrates and evaluate their properties.</p>

DOI： 10.1299/jsmemecj.2018.j2220204

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmetokai.2018.67.219

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmetokai.2018.67.216

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmetokai.2018.67.221

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>Further miniaturization of the diaphragm for capacitive pressure sensor requires thinner structures to deform micro diaphragm sufficiently by small differential pressure. Since stiffness of thinner structures decrease, the influence of internal stress introduced during processing cannot be ignored. In this paper, we proposed methods of controlling the internal stress for micro diaphragm using thin film metallic glasses (TFMGs). We fabricated micro diaphragms using Ru67Zr25Al8 [at.%] TFMGs. The TFMGs were fabricated by a r.f. sputtering system, and then as sputtered TFMGs had compressive internal stress. Subsequently, the as-sputtered TFMGs on Si substrate were annealed at 315-440°C for 5 minutes in vacuum. After annealing, micro diaphragms were fabricated by etching Si substrate using a reactive ion etching system. Although annealing temperatures were lower than glass transition temperature, initial internal stress was relaxed partially by the structural relaxation of the TFMGs during annealing process. While the tensile thermal stress was induced during cooling process at the interface between the substrate and TFMG. Although micro diaphragm was not induced thermal stress at interface between the substrate and TFMG, the tensile stress applied to diaphragm in the radial direction at the edge. When annealing temperatures were between 320°C and 340°C, the internal stress changed from compressive to tensile. A flat diaphragm was obtained when annealed at 330°C or higher. The pressure sensor modeled by diaphragm annealed at 340°C and the virtual electrode plate showed a linearity of 6.48 [%F.S.]. By proposed method, we succeeded the flat diaphragm and showed the method of tension control of the diaphragm.</p>

DOI： 10.1299/jsmemecj.2018.j2220304

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>A diaphragm structure is a fundamental structure in a micro machine such as MEMS. Conventionally, Si has used as a diaphragm material. However, in recent years, in order to make the diaphragm structure more sophisticated and miniaturized, high sensitivity difficult to realize by using Si is required. Therefore, in this study, we aim to create a highly precise diaphragm structure by using the thin film metallic glass which is an amorphous alloy shown glass transition as a new material which meets these demands. Pd₇₇Cu₆Si₁₇ (at. %) and Ru₆₅Zr₃₀Al₅ (at. %) are used for thin film metallic glass. The thin film metallic glasses are deposited on the Si substrates by sputtering. Internal stress of each film is controlled by adjusting Ar pressure during sputtering and annealing after sputtering. The internal stress of the Pd₇₇Cu₆Si₁₇ (at. %) thin film is always tensile stress and it is minimum at an Ar pressure of 0.5 Pa, and its value is 23.6 MPa. Under this condition, we can create a highly precise diaphragm. On the contrary, the internal stress of Ru₆₅Zr₃₀Al₅ (at. %) thin film is always compressive stress in the range of sputtering Ar pressure. So, we try to relax the internal stress of Ru₆₅Zr₃₀Al₅ (at. %) thin film by annealing. In the proper annealing conditions, a diaphragm having the same flatness level as Pd₇₇Cu₆Si₁₇ (at. %) is realized.</p>

DOI： 10.1299/jsmemecj.2018.j2220303

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmetokai.2018.67.702

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmetokai.2018.67.225

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>Surface activated bonding (SAB) is used in three-dimensional laminating technology for such as LSI chips. Ar fast atom beam (FAB) is used for SAB. However, there is a serious problem that the conventional FAB gun can be often used for only hundreds of minutes because abrasion powders are generated from the worn part due to Ar⁺ sputtering in the gun. Therefore, it is the purpose of this work to develop a new FAB gun to realize longer life. We developed the novel FAB gun applied with a magnetic field to control Ar⁺ motion and reduce the sputtering in the gun. Furthermore, the disposition of the carbon electrodes in the gun was changed. As a result, we succeeded in 3 times Ar emission efficiency due to applying the magnetic field. And we unconfirmed abrasion powder in the novel FAB gun after 5200 minutes irradiation experiments. As written above, the novel FAB gun was able to function as expected.</p>

DOI： 10.1299/jsmemecj.2018.j1110203

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmetokai.2018.67.701

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>Cu-based mesh electrodes were directly written using femtosecond laser reductive sintering of CuO nanoparticles. CuO nanoparticle solution containing CuO nanoparticle, polyvynilpyrrolidone, and ethylene glycol was spray-coated on flexible poly(dimethylsiloxane) substrates. Femtosecond laser pulses were focused onto the CuO nanoparticle solution using an objective lens with a numerical aperture of 0.45 in air. When the scan pitch for mesh patterning was more than 25 μm, Cu-rich mesh patterns were formed. The Cu-mesh temperature sensors were fabricated at the scan pitch of 50 μm. The temperature coefficient of the sensor was +0.004, which is consistent with the Cu bulk one. This fabrication process is useful for additive manufacturing on flexible and nonplanar surfaces.</p>

DOI： 10.1299/jsmemecj.2018.s0410103

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We designed and fabricated thin-film thermoelectric generators (TEGs) with ball lenses, which separated visible light and near-infrared (NIR) solar light using a chromatic aberration. The transmitted visible light was used as daylight and the NIR light was used for thermoelectric generation. Solar light was estimated to be separated into the visible light and NIR light by a ray tracing method. 92.7% of the visible light was used as daylight and 9.9% of the NIR light was used for thermoelectric generation. Then, the temperature difference of the pn junctions of the TEG surface was 0.71 K, determined by heat conduction analysis using a finite element method. The thin-film TEGs were fabricated using lithography and deposition processes. When the solar light (A.M. 1.5) was irradiated to the TEGs, the open-circuit voltage and maximum power were 4.5 V/m(2) and 51 mu W/m(2), respectively. These TEGs are expected to be used as an energy supply for Internet of Things sensors. (C) 2017 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.56.06GN06

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Ni-based composite micropatterns were fabricated by the femtosecond laser reductive sintering of NiO/Cr mixed nanoparticles. A NiO/Cr mixed nanoparticle solution including ethylene glycol and polyvinylpyrrolidone was irradiated with focused femtosecond laser pulses. The X-ray diffraction spectra of the fabricated micropatterns indicated that NiO nanoparticles were well reduced under atmospheric conditions in the laser scanning speed range of 5-15mm/s. In contrast, micropatterns including NiO were formed at a laser scanning speed of 1mm/s, indicating that the reduced Ni was reoxidized by overheating. These results were supported by those of energy-dispersive X-ray spectrometry analysis and the electrical resistivity of the micropatterns. The compositions such as Ni, NiO, Cr2O3, and Ni-Cr in the fabricated micropatterns depended on laser scanning speed. The selective fabrication of a ferromagnetic free microgear from the substrate and an axis fixed on the substrate was demonstrated by controlling the laser scanning speed. The fabrication process for Ni-based composite microstructures is useful for the fabrication of ferromagnetic microdevices. (C) 2017 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.56.06GN08

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We have demonstrated the fabrication of two types of thermal flow sensors with Cu-rich and Cu2O-rich microheaters using femtosecond laser-induced reduction of CuO nanoparticles. The microheaters in the shape of microbridge structures were formed to thermally isolate from the substrates by four layer-by-layer laminations of two-dimensional micropatterns. First, we evaluated the patterning properties such as dispensing coating conditions and degree of reduction for the selective fabrication of three-dimensional Cu-rich and Cu2O-rich microstructures. Then, a hot-film flow sensor with a Cu-rich microheater and a calorimetric flow sensor with a Cu2O-rich microheater were fabricated using their respective appropriate laser irradiation conditions. The hot-film sensor with the Cu-rich microbridge single heater enabled us to measure the flow rate in a wide range of 0-450 cc min(-1). Although a large temperature dependence of the Cu2O-rich microbridge heaters caused a large error for the hot-film flow sensors with single heaters, they showed higher heat-resistance and generated heat with a lower drive power. The temperature coefficient of resistance of the Cu2O-rich microstructures had a semiconductor-like large absolute value and was less than -4.6 x 10(-8) degrees C-1. The higher temperature sensitivity of the Cu2O-rich microstructures was useful for thermal detection. Based on these advantages, a calorimetric flow sensor composed of the Cu2O-rich microbridge single heater and two Cu2O-rich thermal detectors was proposed and fabricated. The calorimetric flow sensor was driven by a circuit for measuring the temperature difference. The Cu2O-rich flow sensor could detect bi-directional flow with a small output error.

DOI： 10.1088/1361-6439/aa6820

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Three-dimensional Cu microstructures were formed using a combined process of dispensing coating and femtosecond laser-induced reduction of CuO nanoparticles. Layer-by-layer lamination of two-dimensional Cu micropatterns was performed by alternately coating with a CuO nanoparticle solution and using direct laser writing, followed by the removal of nonirradiated CuO nanoparticles. The resistance of the 3D microstructures decreased as the number of layers increased, indicating that each layer was electrically connected to the others. We also demonstrated the fabrication of a microbridge heater composed of electrode pads and a microbridge, and found that its heating characteristics are suitable for use in microsensors, such as thermal-type flow sensors.

DOI： 1882-0786/10/1/017201

Publisher：2016 International Symposium on Micro-NanoMechatronics and Human Science, MHS 2016  

In this study, we proposed and demonstrated combinatorial evaluation substrates, which were fabricated by micro electro mechanical systems (MEMS) process, for brine electrolysis. Proposed evaluation substrate has 9 electrode catalyst samples on the glass substrate. Ir-Ru/Ti and Ir-Ru-Ti/Ti electrode catalyst samples were prepared by a combinatorial co-sputtering system. We evaluated the maximum current density of polarization curves and the durability during brine electrolysis. In the case of binary Ir-Ru/Ti evaluation substrate (composition of Ru ranged from 35.1 to 58.8 at.%.), the maximum current density increased with increasing Ru-content. From these results, we confirmed the usability of proposed combinatorial evaluation substrate for the brine electrolysis. Finally, we evaluated the electrochemical characteristics of 9 Ir-Ru-Ti/Ti samples. Their electrochemical characteristics depend on alloy composition.

DOI： 10.1109/MHS.2016.7824159

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Applied Physics  

Three-dimensional Cu microstructures were formed using a combined process of dispensing coating and femtosecond laser-induced reduction of CuO nanoparticles. Layer-by-layer lamination of two-dimensional Cu micropatterns was performed by alternately coating with a CuO nanoparticle solution and using direct laser writing, followed by the removal of nonirradiated CuO nanoparticles. The resistance of the 3D microstructures decreased as the number of layers increased, indicating that each layer was electrically connected to the others. We also demonstrated the fabrication of a microbridge heater composed of electrode pads and a microbridge, and found that its heating characteristics are suitable for use in microsensors, such as thermal-type flow sensors.

DOI： 10.7567/APEX.10.017201

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electrical Engineers of Japan  

<p>A moisture-in-oil sensor, with a sandwich structure of Cr nanoporous thin film/polyimide film/Au electrode, was fabricated using a lithographic process, sputter deposition, and chemical dealloying. One of the Cr nanoporous thin films used as a molecular filter was made using oblique incidence film formation and sputter deposition at 2.5 Pa of argon and a 60 degree attaching angle. The fabricated Cr nanoporous thin film consisted of 30-50 nm pore sizes as a result of a “shadowing effect”. A moisture-in-oil sensor made with this Cr nanoporous thin film showed favorable responsiveness in oil, with a response time of about 7 minutes, well within the desired maximum value of 10 minutes. To further improve the responsiveness of the sensor, another Cr nanoporous thin film was prepared using a chemical dealloying process, which facilitates control of the pore sizes. This process consists of co-sputtering Cu and Cr, annealing for 1 h at 573 K and dealloying for 15 h in 32.5% HNO₃. The thin film pore sizes depend on the initial Cu-Cr compositions, which were researched using a combinatorial technique at various fabrication conditions. We investigated a wide compositional range between 32 and 22 at.% Cr. It was found that between 28 and 22 at.% Cr, chemical dealloying results in low residual Cu, less than 10 at.%. The pore sizes obtained were <20 nm for 32 at.% Cr, 20-40 nm for 28 at.% Cr, 40-60 nm for 25 at.% Cr and >60 nm for 22 at.% Cr. The initial composition ratio of 28 at.% Cr was used to fabricate a Cr nanoporous electrode film filter for a moisture sensor. Unfortunately, the final residual Cu composition ratio was 17 at.%, which is more than the desired maximum of 10 at.%, because the thin film had a uniform composition. The changes in the electrostatic capacity of the moisture sensor as a function of relative humidity (50%RH-90%RH) in air were studied, and the sensor output followed changes in the relative humidity.</p>

DOI： 10.1541/ieejsmas.137.15

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Language：English   Publisher：SPIE  

Cu-based micro-temperature sensors were directly fabricated on poly(dimethylsiloxane) (PDMS) blood vessel models in EVE using a combined process of spray coating and femtosecond laser reduction of CuO nanoparticles. CuO nanoparticle solution coated on a PDMS blood vessel model are thermally reduced and sintered by focused femtosecond laser pulses in atmosphere to write the sensors. After removing the non-irradiated CuO nanoparticles, Cu-based microtemperature sensors are formed. The sensors are thermistor-type ones whose temperature dependences of the resistance are used for measuring temperature inside the blood vessel model. This fabrication technique is useful for direct-writing of Cu-based microsensors and actuators on arbitrary nonplanar substrates.

DOI： 10.1117/12.2265050

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Language：English   Publisher：SPIE  

Copper (Cu)-based micropatterns were fabricated on polymer substrates using femtosecond laser reduction of copper (II) oxide (CuO) nanoparticles. CuO nanoparticle solution, which consisted of CuO nanoparticles, ethylene glycol as a reductant agent, and polyvinylpyrrolidone as a dispersant, was spin-coated on poly(dimethylsiloxane) (PDMS) substrates and was irradiated by focused femtosecond laser pulses to fabricate Cu-based micropatterns. When the laser pulses were raster-scanned onto the solution, CuO nanoparticles were reduced and sintered. Cu-rich and copper (I)-oxide (Cu2O)-rich micropatterns were formed at laser scanning speeds of 15 mm/s and 0.5 mm/s, respectively, and at a pulse energy of 0.54 nJ. Cu-rich electrically conductive micropatterns were obtained without significant damages on the substrates. On the other hand, Cu2O-rich micropatterns exhibited no electrical conductivity, indicating that microcracks were generated on the micropatterns by thermal expansion and shrinking of the substrates. We demonstrated a direct-writing of Cu-rich micro-temperature sensors on PDMS substrates using the foregoing laser irradiation condition. The resistance of the fabricated sensors increased with increasing temperature, which is consistent with that of Cu. This direct-writing technique is useful for fabricating Cu-polymer composite microstructures.

DOI： 10.1117/12.2261398

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Thermoelectric couples which consisted of p-type and n-type thermoelectric elements were directly written on glass substrates using femtosecond laser reduction of CuO/NiO mixed nanoparticles. CuO/NiO nanoparticle solution including CuO and NiO nanoparticles, ethylene glycol, and polyvinylpyrrolidone, was spin-coated on glass substrates. Then, p-type and n-type thermoelectric elements were formed by raster scanning of focused femtosecond laser pulses. After rinsing the samples into ethylene glycol and ethanol, the thermoelectric couples were fabricated on the substrates. Cu–Ni- and Cu₂O/NiO-rich micropatterns were selectively formed by controlling the laser scanning speed. The Cu–Ni-based and Cu₂O/NiO-based micropatterns exhibited n-type and p-type thermoelectric properties, respectively. An open-circuit voltage of the fabricated thermoelectric couple was 0.25 mV/K which was almost consistent with the estimated values using each Seebeck coefficient of the p-type and n-type thermoelectric elements. This selective direct-writing process of p-type and n-type thermoelectric materials is useful to fabricate various thermoelectric-type sensors.

DOI： 10.1299/jsmemnm.2017.8.pn-17

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

We prepared poly(dimethylsiloxane) (PDMS)-based microparts and fabricated hexagonal periodic structures by selfassembly. Periodic structures of PDMS are advantageous for the development of micro-optical devices because of the high transparency of PDMS in a wide range of wavelengths, including visible light. PDMS microparts were fabricated using the combination of photolithography and ultra-violet ozone treatment. The shape of the microparts was hexagonal prism consisting a hole in the center. The side lengths and the height were 10 μm and 8 μm, respectively. Self-assembly was progressed by the coffee-ring effect that flow the microparts toward outside of the suspension droplet that consisted of PDMS microparts and deionized water. A diffraction pattern was observed by laser irradiation to the self-assembled periodic structures. The ring pattern indicates that series of periodic structures were partially formed on the template.

DOI： 10.1299/jsmemnm.2017.8.pn-70

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>We evaluated microforming ability and shape memory behaviors of Ti₃₈Ni₅₀Zr₁₂ (at.%) high formable shape memory alloys (HFSMAs) for the fabrication of the micro folding structure such as foldable pipe structures. In the fabrication method of foldable pipe, at first, Ti-Ni-Zr thin film metallic glass (TFMG) sheet is creased by using micro jigs in the supercooled liquid region. Secondary, the both side edges of the sheet with creases are bonded together to make pipe structure. Finally, TFMG pipe with creases is annealed to be became SMAs. To foldable fabricate pipe structure, we evaluated microforming ability, shape memory behavior of folded SMAs, and bonding conditions. We succeeded to fabricate folded specimens with folding angle <i>θ</i> of 60° and 90°. In order to investigate shape memory behaviors, folded specimens were annealed at 873 K for 1 hour and become SMAs. Their shape memory behaviors were evaluated by bending tests during several thermal cycles, they showed good shape memory behaviors. We confirmed that folded specimens with folding angle <i>θ</i> of 60° and 90° can recover its shape without plastic deformation even if it was deformed to straight shape (<i>θ</i>=180°). We evaluated bonding conditions by using micro jigs between HFSMAs and bonding strength. As the results, when bonding pressure was 75 MPa, we succeeded the bonding process using viscous flow or diffusion bonding. Bonding strength increased with increasing bonding temperature. When bonding temperature was 673 K, the bonded specimen was crystallized and show bonding strength of more than 2.5 MPa. However, when bonding temperature was over 723 K, the specimens stuck with micro jig.</p>

DOI： 10.1299/jsmemecj.2017.j2220105

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In this paper, we proposed the combinatorial evaluation method of thermal properties such as glass transition temperature <i>T</i>_g and crystallization temperature <i>T</i>_x for Ti-Ni-X high formable shape memory alloys (HFSMAs). We fabricated the integrated library consisting of 5 samples with different alloy compositions. This library was prepared by carousel type co-sputtering system using metal shadow masks. Alloy composition distribution of this library had homogeneous in one direction (RD direction). In contrast, in another direction (TD direction), this library had compositionally graded alloy composition. Finally, we combinatorial-evaluated thermal properties of 5 Ti-Ni-Zr amorphous samples on the library. 3 samples showed glass transition, and they were thin film metallic glasses. Specifically, they were HFSMAs. Other 2 samples did not show glass transition, and they were only amorphous sample (only SMAs). These results agreed with the results of previous paper using conventional sequential evaluation methods.</p>

DOI： 10.1299/jsmemecj.2017.j2220104

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In this research, we investigated high throughput evaluation method of magnetostriction and relative permeability for magnetostrictive materials using MEMS device. MEMS device is fabricated by bonding process of evaluation substrate which consist of pick up coil and vibrating electrode, and sample substrate which is fabricated on the SOI wafer. The resonance frequency of fabricated cantilever sample is 6.6 kHz which is measured by using frequency response analyzer, applied voltage between sample surface and vibrating electrode is 80 Vpp. Vibrating state is measured by using Laser Doppler Vibrometer. The magnetization of the sample is evaluated from the output voltage of pick up coil placed near the cantilever sample. Rock in amplifier is used for the measurement of voltage of pick up coil. The output voltage is increased as long as increasing applied magnetic field. This result shows the possibility to measure magnetization of magnetic materials using proposed MEMS device. In this paper, we show the evaluation result of resonance frequency and magnetization curve of fabricated MEMS device.</p>

DOI： 10.1299/jsmemecj.2017.j2220103

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>We evaluated the self-assembling properties of fabricated poly(dimethylsiloxane) (PDMS)-based microparts. The PDMS-based microparts, which are advantageous for use in optical devices due to their high transparency in ultraviolet (UV) to near infrared light, were fabricated and assembled. The microparts were prepared by photo-lithography and UV-ozone treatment processes. The size of the microparts was 20 μm and the shape was a hexagonal prism to form hexagonal close-packed by self-assembly. The microparts were prepared approximately 2×10⁵ numbers on a glass substrate, following that they were separated from substrate by sonicating in acetone. The suspension including microparts was prepared by evaporating acetone and adding water and surfactant F-127. The microparts were self-assembled by using the capillary force and the coffee-ring effect. The suspension including microparts and water was dripped to the template glass substrates which had photoresist patterns. Microparts were self-assembled by the coffee-ring effect which occurred with water volatilization. Finally, the PDMS-based periodic structures were successfully formed by self-assembled hexagonal close-packed of microparts.</p>

DOI： 10.1299/jsmemecj.2017.j2220203

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>We investigated defocus direct-writing properties of Cu micropatterns on planar poly(dimethylsiloxane) (PDMS) substrates in femtosecond laser reduction of CuO nanoparticles (NPs). The Cu lines written at defocus position of every 1 μm from -5 to 5 μm had almost uniform width, 20±1 μm, at a numerical aperture (NA) of 0.45. The crystal structures of the micropatterns which were formed at the defocus positions of -5, 0, and 5 μm were also evaluated. The micropatterns were formed at the pulse energy of 0.45 nJ, scan pitch of 5 μm, and various scan speed. Regardless of the defocus position, the degree of reduction of micropatterns exhibited the same properties. When scan speed was larger than 10 mm/s, Cu-rich micropatterns were obtained. When scan speed was 5 mm/s, Cu₂O-rich micropatterns were formed. Finally, Cu-based mesh micropatterns were fabricated at various laser scan pitch. When scan pitch was determined as 25 μm and 50 μm, Cu-rich mesh micropatterns were formed at 5 mm/s. The temperature coefficient of resistance of Cu-rich mesh micropatterns with the pitch of 25 μm was 0.005/°C, which was as small as expected values.</p>

DOI： 10.1299/jsmemecj.2017.s0460101

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>Magnetostrictive materials are applicable to various types of sensors. In order to increase the resolution of the sensor, materials with high magnetostriction amount and relative permeability are required and Fe-Ni-Cr alloys are expected to have excellent magnetic properties. For searching materials with ideal properties, combinatorial search is one of the effective method. In this study, integrated SOI-MEMS device for combinatorial search is fabricated. This device is designed to perform combinatorial search of magnetostriction amount and relative permeability of Fe-Ni-Cr alloys.</p>

DOI： 10.1299/jsmemecj.2017.j2220102

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>Photoelastic stress measurement of PVA hydrogel for vessel model was investigated. In order to apply to the vessel model, the properties of PVA hydrogel were evaluated. Young's modulus of PVA hydrogel is 0.06-0.45 MPa, which is useful for reproducing soft vascular tissue. The photoelastic coefficient of PVA hydrogel is 1.60×10^-9 Pa^-1, which is useful for photoelastic stress measurement. We constructed a new photoelastic observation system that can measure the value and direction of stress from only RGB values. In order to minimize the overlap ratio of the same color in color map, the number of 1 wave plate is 2 and the insertion angle is 30 degrees. Furthermore, a program was developed to output stress distribution images by image processing using this photoelastic observation system. As a result of photoelastic stress measurement of PVA hydrogel under tensile loading, measurement was successful with an error of 6.0%, which is sufficient accuracy.</p>

DOI： 10.1299/jsmemecj.2017.j0470302

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>We demonstrated the fabrication of Cu/Cu-Ni thin-film thermoelectric generators for energy harvest. The device consisted of 50 pairs of Cu/Cu-Ni thermocouples. The widths of the Cu (p-type) and Cu-Ni (n-type) thermoelectric elements were 75 μm and 225 μm, respectively. The length of the both elements was 5 mm. Cu and Cu-Ni thin films were deposited on glass substrates using radio-frequency magnetron sputtering method and formed by lift-off techniques. Cu plate was connected the cold sides of the pn junctions using Ag paste. The compositions of Cu and Ni in the deposited thin films using a Cu₆₀Ni₄₀ alloy target were 58.5(±1.4)at% and 41.5(±0.9)at%, respectively, indicating that significant oxidation of the thin films were not observed. The generation properties of the fabricated 5 devices, which were connected in series, were evaluated. When the hot sides of the devices were heated at 55.4°C using a hot plate as a thermal source, the temperature difference of between the hot and cold sides was approximately 18°C. The open-circuit voltage and maximum power were 192 mV and 1.46 μW (0.65 mW/m²), respectively.</p>

DOI： 10.1299/jsmemecj.2017.j2220202

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In our previous study, a nano-porous film was fabricated by a Cu-Cr dealloying concluding an annealing process, which play a role in a thermal coarsening of an as-deposited Cu-Cr film. Because of the thermal coarsening, metal grains were grown, thus Cu was easily dealloyed from an as-deposited Cu-Cr film. However sensor materials were restricted due to a high coarsening temperature. In this study, a novel Cu-Cr dealloying was introduced, in which process high sputtering pressure and low sputtering power supply the place of the annealing process. A Cu₈₂Cr₁₈ film with an area with dimensions 2 mm×5 mm was fabricated on a polyimide by co-sputtering for 35 min at 2.5 Pa of argon, at 175 W for the Cu target and 80 W for the Cr target. The so fabricated film was immersed in 22.5% HNO₃ for 30 minutes at room temperature. As a result, Cu was dealloyed from the as-deposited Cu₈₂Cr₁₈ film, ant its composition changed into Cu₂₅Cr₇₅. Furthermore, an appearance of the film changed from Cu brown to transparent appearance. As a reason of the transparency, a chromium oxide was formed. In addition, a nanoporous structure with 20-40 nm pores was successfully observed using FE-SEM. This nano-porous film was applied for an upper electrode of a moisture sensor which takes sandwich structure of an upper electrode/a polyimide/a lower electrode. The fabricated sensor showed a good responsibility in the air and a good hysteresis of 9.3%F.S., which was within the desired value of 10.0%F.S..</p>

DOI： 10.1299/jsmemecj.2017.j2220201

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>We performed combinatorial searching of suitable Ir-Ru-TiO₂/Ti system electrode catalysts for brine electrolysis. Proposed combinatorial evaluation substrates were fabricated by micro electro mechanical systems (MEMS) process. 9 Ir-Ru-TiO₂/Ti electrode catalysts were prepared on the glass substrate by a combinatorial co-sputtering system. As characteristics of electrode catalyst, the maximum current density and the durability was evaluated during brine electrolysis in NaCl solution of 30 g/L. The measurement of the maximum current density was performed by linear sweep voltammetry. Durability was evaluated by observation of catalyst surface and X-ray diffractometry before and after brine electrolysis. As the results of linear sweep voltammetry, Ir_24.3Ru_35.3Ti_40.4 electrode catalyst exhibited the highest maximum current density among 51 fabricated Ir-Ru-TiO₂/Ti samples, and showed approximately 1.5 times higher maximum current density than Ir_25.1Ru_26.2Ti_48.7 electrode catalyst having the composition near DSE (Dimensionally Stable Electrode), which is used for industrial electrode catalyst for brine electrolysis. Ir_24.3Ru_35.3Ti_40.4 electrode catalyst showed good durability for brine electrolysis.</p>

DOI： 10.1299/jsmemecj.2017.j2220101

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>We investigated mechanical properties and photoelastic coefficient of designable-gel, double network gel, for fabricating vessel models. Designable-gel samples were prepared with different material ratios, and especially crosslinker(MBAA) 27 mM samples were prepared by molding and shaping with 3D gel printer “SWIM-ER” (Prof. Furukawa et al., Yamagata Univ.). Moreover, the stress occurring in the sample was measured by the photoelastic stress measurement system using photoelastic effect and image processing, developed by our group, and the error between the tensile test result and the measurement system result was evaluated. The young's modulus of designable-gel was found to be 0.12 - 0.77 MPa for strain 0 - 15%, and 0.22 - 1.3 MPa for 15% ~, and is within the young's modulus of human vessels. Therefore, designable-gel was shown to be useful for reproducing human vessels. The photoelastic coefficient of designable-gel was 0.012 - 0.022 ×10^-9 Pa^-1, and is effective for measuring stress by photoelastic effect. The error between the tensile test result and the measurement system result was 7.3%. The vessel model made of designable-gel can be applied to the photoelastic stress measurement system, because the error is small and acceptable.</p>

DOI： 10.1299/jsmemecj.2017.j0470305

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Cu-based mesh-thermal detector was fabricated using femtosecond laser reduction patterning on planer glass substrate. First, the width of line patterns formed in various scan speed were evaluated. Then, the lattice structures of the micropatterns formed in scan speed of 5 mm/s, scan pitch of 5 or 25 μm were examined using X-ray diffraction analysis. When the scan pitch was 25 μm, the lattice patterns were Cu-rich materials with the electrical resistivity of 4.1×10^-5 Ωm. Cu₂O-rich patterns with the electrical resistivity of 1.2×10^-1 Ωm were obtained when the scan pitch was 5 μm. Finally, we demonstrated the fabrication of Cu-based mesh-thermal detectors with the scan pitch of 25 μm. The thermal detector provided the plus temperature coefficient of resistance of 0.002/ºC. This mesh patterning technique is useful for fabricating microdevices such as sensors.

DOI： 10.1299/jsmemnm.2017.8.pn-16

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Fuji Technology Press Ltd.  

<p>We investigated the effect of different solvents on the Cu micropatterns formed via femtosecond laser reduction patterning. Solvents such as ethylene glycol, 2-propanol, and glycerol were mixed with CuO nanoparticles and polyvinylpyrrolidone. The degree of reduction and the resistivity of the fabricated micropatterns depended on the solvent. Glycerol was the most effective reducing agent. This solution was used to fabricate Cu/Cu₂O composite micro-temperature sensors. Cu-rich electrodes and Cu₂O-rich sensors were selectively formed by controlling the laser scanning speed at 5 mm/s and 0.5 mm/s, respectively, when the pulse energy was 0.53 nJ. The temperature sensor exhibited a negative temperature coefficient of the resistance, which was consistent with the value for Cu₂O.</p>

DOI： 10.20965/ijat.2016.p0934

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DOI： 10.4172/2321-6212.1000155

Language：English   Publisher：IOP publishing  

Micro-temperature sensors, which composed of a Cu<inf>2</inf>O-rich sensing part and two Cu-rich electrodes, were directly fabricated by femtosecond laser reduction patterning of CuO nanoparticles. Patterning of the microstructures was performed by laser scanning with pitches of 5, 10, and 15 µm. Cu<inf>2</inf>O-rich micropatterns were formed at the laser scan speed of 1 mm/s, the pitch of 5 µm, and the pulse energy of 0.54 nJ. Cu-rich micropatterns that had high generation selectivity of Cu against Cu<inf>2</inf>O were fabricated at the laser scan speed of 15 mm/s, the pitch of 5 µm, and the pulse energy of 0.45 nJ. Electrical resistivities of the Cu<inf>2</inf>O- and Cu-rich micropatterns were approximately 10 Ω m and 9 µΩ m, respectively. The temperature coefficient of the resistance of the micro-temperature sensor fabricated under these laser irradiation conditions was −5.5 × 10⁻³/°C. This resistance property with a negative value was consistent with that of semiconductor Cu<inf>2</inf>O.

DOI： 10.7567/JJAP.55.06GP05

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Language：English   Publisher：IOP publishing  

We fabricated antireflection structures (ARSs) on the hot side of a thermoelectric generator (TEG) to absorb near-infrared (NIR) solar light with low reflective energy loss. First, the ARSs, composed of a CuO thin-film coated hemisphere array were designed using rigorous coupled wave analysis. Reflective loss was reduced to 6.7% at a grating period of 200 nm, as determined by simulation. Then, the ARSs were fabricated on a glass substrate using self-arranged submicron SiO<inf>2</inf>spheres, following the coating of a CuO thin film. Finally, the effect of the ARSs on NIR solar light generation was investigated by evaluating the generation properties of the TEG with the ARSs on the hot side. In comparison with the TEG with the CuO flat thin film on the hot side, the ARSs increased the temperature difference between the hot and cold sides by approximately 1.4 times. The CuO-based ARSs absorbed NIR solar light effectively.

DOI： 10.7567/JJAP.55.06GP07

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 1347-4065/55/6S1/06GP07

Language：English   Publishing type：Research paper (scientific journal)  

Micro-temperature sensors, which composed of a Cu2O-rich sensing part and two Cu-rich electrodes, were directly fabricated by femtosecond
laser reduction patterning of CuO nanoparticles. Patterning of the microstructures was performed by laser scanning with pitches of 5, 10, and
15 µm. Cu2O-rich micropatterns were formed at the laser scan speed of 1 mm/s, the pitch of 5 µm, and the pulse energy of 0.54 nJ. Cu-rich
micropatterns that had high generation selectivity of Cu against Cu2O were fabricated at the laser scan speed of 15 mm/s, the pitch of 5 µm, and
the pulse energy of 0.45 nJ. Electrical resistivities of the Cu2O- and Cu-rich micropatterns were approximately 10 Ω m and 9 µΩ m, respectively. The
temperature coefficient of the resistance of the micro-temperature sensor fabricated under these laser irradiation conditions was %5.5 ' 10%3/°C.
This resistance property with a negative value was consistent with that of semiconductor Cu2O. © 2016 The Japan Society of Applied Physics

DOI： 1347-4065/55/6S1/06GP05

Language：Japanese  

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

In this study, we proposed to search for new electrode catalyst for the electrolysis of brine using a combinatorial method. The evaluation substrate consisting of 72 catalyst samples and 9 Pt reference electrodes was designed and fabricated by micro electro mechanical system (MEMS) techniques. The thin film electrode catalyst library on the evaluation substrate was prepared by a combinatorial multi target sputtering system. To evaluation the characteristics of catalyst samples, the polarization curves (current density/potential curves) of catalyst samples were measured by the potential sweep method. Surface poisoning and elution of catalysis samples were observed by an optical microscopy. Finally, we confirmed that the proposed combinatorial method was useful to search for new electrode catalytic materials.

DOI： 10.1109/MHS.2015.7438321

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

A thin-film thermoelectric generator (TEG) with ball lenses which enable the visible light to pass through was designed and fabricated. When diameters of the ball lens and the pinhole were 6 mm and 200 μm, respectively, 76% of the visible light and 36% of the infrared light were transmissive to the TEG under the condition that the ball lens position from the device substrate was 0 μm. Thin-film TEGs were fabricated using lithography and thermoelectric thin film deposition processes. The thin film thermoelectric elements were formed on the glass substrate without removal by inserting the Cr buffer layers between the thermoelectric thin films and the substrate. The width of the elements were up to 10 μm greater than that of the designed one. The difference between the fabricated and the designed one was less than 10%, which is negligible value for the internal resistance of the TEGs.

DOI： 10.1109/MHS.2015.7438318

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Language：English   Publisher：Institute of Physics  

Cu-based micro-temperature detectors were fabricated using femtosecond laser reduction of CuO nanoparticles. Cu-based microstructures were directly created by laser scanning on a CuO nanoparticle solution film. Cu-rich and Cu<inf>2</inf>O-rich microstructures were selectively formed to electrically connect two Cu thin-film electrodes for use in temperature detectors. Cu-rich and Cu<inf>2</inf>O-rich micro-temperature detectors were fabricated at scanning speeds of 500 and 1000 µm/s, respectively, at a pulse energy of 1.2 nJ. The temperature coefficient of resistance values of the Cu-rich and Cu<inf>2</inf>O-rich microstructures were positive and negative, respectively; these temperature behaviors are typical of metal and semiconductor materials, respectively.

DOI： 10.7567/APEX.9.036701

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人 日本機械学会  

DOI： 10.1299/jsmemag.119.1170_300

CiNii Research

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this study, we proposed and demonstrated combinatorial evaluation substrates, which were fabricated by micro electro mechanical systems (MEMS) process, for brine electrolysis. Proposed evaluation substrate has 9 electrode catalyst samples on the glass substrate. Ir-Ru/Ti and Ir-Ru-Ti/Ti electrode catalyst samples were prepared by a combinatorial co-sputtering system. We evaluated the maximum current density of polarization curves and the durability during brine electrolysis. In the case of binary Ir-Ru/Ti evaluation substrate (composition of Ru ranged from 35.1 to 58.8 at.%.), the maximum current density increased with increasing Ru-content. From these results, we confirmed the usability of proposed combinatorial evaluation substrate for the brine electrolysis. Finally, we evaluated the electrochemical characteristics of 9 Ir-Ru-Ti/Ti samples. Their electrochemical characteristics depend on alloy composition.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In this paper, we investigated the temperature dependence of electrical resistance of amorphous Ti-Ni-Zr high formable shape memory alloys (HFSMAs) for combinatorial measurement of glass transition temperature (<i>T_g</i>) and crystallization temperature (<i>T_x</i>). The electrical resistances of the Ti-Ni-Zr amorphous samples (ie. thin film metallic glasses: TFMGs) were measured using a four-terminals method. The samples were heated by a SiC heater in the vacuum chamber with heating rate of 10 K/min. The <i>T_g</i> and <i>T_x</i> were also measured by a differential scanning calorimetry (DSC) with heating rate of 10 K/min. We confirmed that the electrical resistance of Ti₃₂Ni₅₁Zr₁₇ (at.%) TFMG decreased slightly at the <i>T_g</i> of 697 K. Moreover, the electrical resistance was decreased drastically over the <i>T_x</i> of 741 K. On the other hand, the <i>T_g</i> and <i>T_x</i> measured by the DSC measurement were 712 K, 763 K, respectively. The difference of thermal properties between two measurements was caused by the accuracy temperature measurement of heating equipment for measuring electric resistance.</p>

DOI： 10.1299/jsmemecj.2016.j2240101

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>Micro forming method of Ti-Ni-Zr high formable shape memory alloys (HFSMAs) using viscous flow in supercooled liquid region (SCLR) was investigated. Planer Ti₃₈Ni₅₀Zr₁₂ (at.%) samples were prepared by r.f. magnetron sputtering and were thin film metallic glasses (TFMGs). Glass transition temperature (<i>T_g</i>) and crystallization start temperature (<i>T_x</i>) were 704 and 764 K, respectively. SCLR (=<i>T_x</i> -<i>T_g</i>) was 60 K. Planer specimens were deformed and fixed using micro jigs. When they were heated to around the SCLR, the stress relaxation occurred by their viscous flow. We investigated heating conditions to stress-relax completely. Finally, we successfully obtained waved Ti₃₈Ni₅₀Zr₁₂ TFMGs in room temperature. The waved Ti₃₈Ni₅₀Zr₁₂ TFMG samples were annealed at 873, 973, 1073 K for 1 hour in order to crystallize and become waved SMAs. Martensitic transformation start temperature and the reverse martensitic transformation start temperature also increased with increasing the annealing temperature. These SMA samples exhibited a shape memory effect and/or superelasticity.</p>

DOI： 10.1299/jsmemecj.2016.j2240105

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>We designed and fabricated thin-film thermoelectric generators (TEGs) with ball lenses on a glass substrate that transmit the visible solar light and convert the near-infrared (NIR) solar light to electric energy. In the calculation, the ball lenses separated the visible light and the NIR light using the chromatic aberration to defocus the NIR light and to focus the visible light onto the glass substrates. The NIR light was irradiated onto the hot sides of pn junctions on the glass substrate. The visible light was transmitted the glass substrate to use as daylight through the pin hole in the center of the TEGs. The torus-shaped TEGs which composed of serially connected pn junctions were designed using ray tracing method. The outer and inner diameters of the TEG were 1000 μm and 52 μm, respectively. The TE thin-film elements (p-type: Bi_0.5Sb_1.5Te₃, n-type: Bi₂Te_2.7Se_0.3) were formed using lithography and radio-frequency magnetron sputtering. The generation properties and the open-circuit voltage and the maximum generation power were 0.076 mV/pair and 0.018 nW/pair, respectively when the solar light was irradiated at 298K.</p>

DOI： 10.1299/jsmemecj.2016.j2240204

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In order to apply the magnetostrictive materials to the sensor, the magnetostrictive materials are required to have a large magnetostriction and high relative permeability. We have studied the high throughput evaluation method using the MEMS device to search for materials having such characteristics. The MEMS device has a structure of the cantilever to measure the magnetostriction and relative permeability. However, it is difficult to measure magnetostrictive properties accurately because of a deflection of the cantilever. The purpose of this study is reduction of the deflection of the cantilever using internal stress relaxation of the thin film metallic glasses. We carried out heat treatment of Pd-Cu-Si deposited on a Si substrate. From the results, the conditions for internal stress relaxation of Pd-Cu-Si were searched. Using these conditions, heat treatment of the micro-structures consisted of Pd-Cu-Si and Fe-Ni-Cr was carried out. As a result, we succeeded in reducing the deflection of the micro-structures.</p>

DOI： 10.1299/jsmemecj.2016.j2240102

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>We prepared 10 μm-sized poly(dimethylsiloxane) (PDMS)-based cubic microparts to form 3D microperiodic structures by self-assembly of the microparts. Self-assembly is a promising candidate for fabricating the 3D periodic structures such as optical microdevices. The PDMS-based microparts, which have high transparency in ultraviolet (UV) to near infrared (NIR) light, were fabricated by a combined process of photolithographic techniques and UV-ozone treatment. First, cubic molds of thick photoresist were formed by the lithography. Then, PDMS filled into the molds, following that it was cured by heating at 80°C. After that, the microparts were separated using UV-ozone treatment and ultrasonic microwaves. The microparts were dispersed into the water an ethanol mixed solution with surfactant F-127 to prepare the suspension. The surfactant was useful to prevent aggregation of microparts. Finally, we demonstrated the self-assembling of the PDMS microparts by putting a droplet of the suspension on a glass substrate, and drying at room temperature with turning substrate upside down. The microparts were partly aligned with the cubic closed packing by self-assembly. This result indicates that PDMS-based cubic microparts have possibility of forming three-dimensional periodic structures.</p>

DOI： 10.1299/jsmemecj.2016.j2240201

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>Cr nano-porous electrode film filter could be prepared by co-sputtering Cu and Cr, followed by annealing for 1 h at 573 K and dealloying for 15 h in 32.5% HNO3. Its pore-sizes depend on initial Cu-Cr compositions. To control pore sizes of the nano-porous Cr thin film, initial Cu-Cr compositions for the fabrication conditions was researched by using combinatorial technique. We investigated a wide compositional range between 32 and 22 at.% Cr. Between 28 and 22 at.% Cr, dealloying produces low residual Cu composition ratio less than 10 at.%. The pore sizes obtained were <20 nm for 32 at.% Cr, 20-40 nm for 28 at.% Cr, 40-60 nm for 25 at.% Cr and >60 nm for 22 at.% Cr. The initial composition ratio of 28 at.% Cr was tested for fabricating a Cr nano-porous electrode film filter for a moisture sensor which takes sandwich structure of the nano-porous Cr thin film/polyimide film/Ag electrode. The final residual Cu composition ratio was 17 at.%, not less than 10 at.%, because of using a thin film with uniform composition. The changes in electrostatic capacity of the moisture sensor to changes in relative humidity (50%RH-90%RH) was studied, and the sensor exhibited the followability to changes in relative humidity in the air.</p>

DOI： 10.1299/jsmemecj.2016.j2240203

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In this study, we proposed and demonstrated combinatorial evaluation substrates, which were fabricated by micro electro mechanical systems (MEMS) process, for brine electrolysis. Proposed evaluation substrate has 9 catalyst electrode samples on the glass substrate. Ir-Ru/Ti and Ir-Ru-Ti/Ti alloy catalyst electrode samples were prepared by a combinatorial co-sputtering system. We evaluated the maximum current density of polarization curves and the durability during brine electrolysis. Their polarization curves were measured by a linear sweep voltammetry in NaCl solution of 30 g/L. Measurement system consisted of beaker cell, potentiostat/galvanostat, function generator, and data logger. In this measurement, working electrodes were fabricated catalyst electrodes, reference electrode was Ag|AgCl electrode, counter electrode was Zr plate. Durability was evaluated by the observation of catalyst surface and X-ray diffractometry before and after brine electrolysis. In the case of binary Ir-Ru/Ti evaluation substrate (composition of Ru ranged from 35.1 to 58.8 at.%.), the maximum current density increased with increasing Ru-content. From these results, we confirmed the usability of proposed combinatorial evaluation substrate for brine electrolysis. Finally, we evaluated electrochemical characteristics of 9 Ir-Ru-Ti/Ti samples. Their electrochemical characteristics depend on alloy composition.</p>

DOI： 10.1299/jsmemecj.2016.j2240103

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>We proposed new passive drag delivery system (DDS), which consists of flexible pad as medicine tank, medicine reservoir with medicine sending membrane, microvalves using photoprocessible thermoresponsible gel, and so on. The DDS makes use of external force by normal activities of daily life to administrate liquid medicine and controls administration timing by microvalves using MEMS technology. Therefore, the DDS has advantage of lower power consumption than micropump DDS and higher controllability than percutaneous absorption DDS. We fabricated the medicine sending part of new passive DDS and evaluated characteristics for administrating liquid medicine. At that time, the DDS was filled with DI water and tested under external force. As a result, it was confirmed that the DDS was possible to repeatedly administrate DI water every 2 minutes. Moreover, it was revealed that the DDS could administrate more than 70% of DI water in medicine tank.</p>

DOI： 10.1299/jsmemecj.2016.j2230101

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Fuji Technology Press Ltd.  

<p>In this paper, we investigate the characteristics of Ti-Ni-Zr thin film metallic glasses (TFMGs)/ shape memory alloys (SMAs) for microelectromechanical systems (MEMS) applications with three-dimensional structures. The amorphous Ti-Ni-Zr thin films having a Ni content of more than 50 at.% and Zr content of more than 11 at.% undergo glass transitions and are TFMGs. The Ti₃₉Ni₅₀Zr₁₁ TFMG has the lowest glass transition temperature T_g of 703 K and a wide supercooled liquid region ΔT of 57 K. Moreover, it has high thermal stability at T_g. However, the apparent viscosity of the Ti₃₉Ni₅₀Zr₁₁ is higher than those of other Ti-Ni-Zr TFMGs. Moreover, the Ti-Ni-Zr TFMG exhibits higher viscosity than conventional TFMGs because the alloy composition of Ti-Ni-Zr TFMGs/SMAs is far from the eutectic point.</p>

DOI： 10.20965/ijat.2015.p0662

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Fuji Technology Press Ltd.  

<p>In technologies involving micro electromechanical systems, lift-off processes combined with sputter deposition are general patterning methods for the formation of amorphous alloy thick film structures. However, the thicknesses of structures fabricated in this manner are not uniform because sputtered particles are blocked by the sidewalls of the lift-off layer. In this paper, a reverse lift-off process is proposed as a new patterning method for fabricating amorphous alloy thick film structures of uniform thickness. In the reverse lift-off process, a template of the desired structure is formed on top of the chosen substrate. The thick film structure is then formed by sputter deposition on the top surface of the template. In contrast to a conventional lift-off process, here the thickness of the structure is uniform because there is nothing to hinder the sputtered particles. To demonstrate this process, we successfully fabricated a Cu-Zr-Ti metallic glass thick film structure with a uniform film thickness and a rectangular cross section across different target structure widths and thicknesses. This demonstrates that the reverse lift-off process is more suitable than conventional lift-off processes for the fabrication of metallic glass thick film structures.</p>

DOI： 10.20965/ijat.2015.p0646

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Cu-based microstructures were directly patterned using femtosecond laser-induced CuO nanoparticle reduction. CuO nanoparticle-based solution, consisting CuO nanoparticles, ethylene glycol, and polyvinylpyrrolidone, was spin-coated on glass substrates. Microstructures were formed by irradiating focused femtosecond laser pulses. Cu and Cu2O peak intensities were observed in the X-ray diffraction (XRD) spectra of the microstructures. Compared to single scan, the Cu peak intensities increased by double scan. This result suggests that double scan is effective for increasing the amount of Cu from CuO nanoparticle solution. Cu- and Cu2O-rich microstructures were formed selectively by controlling laser irradiation conditions. The resistivity of the Cu-rich microstructures was estimated by 528 mu Omega m which was 10(4) times and 10 times larger than the values of Cu and Cu2O, respectively. This large resistivity could be applied for microheaters. (C) 2015 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.54.06FP07

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DOI： 10.1299/jsmemipe.2015._MoB-2-2-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

In micro-electro-mechanical systems (MEMS) technology, one of the conventional patterning methods used for metallic thin films is the lift-off process using a photoresist material. However, there is concern regarding the photoresist material generating gas due to the long-term annealing or the high power used in sputter deposition. Thin-film amorphous alloys, such as thin-film metallic glass (TFMG), when used in the device, become crystallized by such heating and outgassing during sputtering. Unlike photoresist material, a metal mask does not generate gas during sputtering. However, a metal mask is subject to deformation by the stress in the sputtered film on the mask. The pattern shape of the TFMG structure can thus collapse due to this mask deformation. Its cross-sectional shape then deviates significantly from a rectangle. We propose a novel lift-off process using a double metal mask for reducing changes in the cross-sectional shape, and maintaining the amorphous nature of the TFMG structure. The characteristic of the double metal mask lift-off process is duplication of the metal mask for restraint of the lower metal mask deformation. Since nearly all of the sputtered material is deposited on the upper metal mask, the material is only minimally deposited onto the lower metal mask. In this work, the double metal mask lift-off process was compared with the conventional lift-off process, and important points for using the double metal mask lift-off process were elucidated. Using the double metal mask lift-off process, a very thick amorphous TFMG structure could be obtained, as compared to the conventional lift-off process. To maintain the rectangular cross-sectional shape of the structure, it was found to be necessary to decrease the height of the double metal mask, as compared to the conventional lift-off process, in anticipation of upper metal mask deformation. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.mee.2015.02.041

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Publisher：2014 International Symposium on Micro-NanoMechatronics and Human Science, MHS 2014  

Combinatorial New-Facing Targets Sputtering (combi-NFTS) is one of the co-sputtering method applied to the combinatorial method. Combi-NFTS could easily control the composition range by changing the distance from substrate to targets. Furthermore composition gradient is relatively linear comparing to other thin film deposition method. In this paper, the influence of the distance between target and target gives for the composition distribution is investigated. As a result, it was elucidated that composition distribution and gradient increase as the TT distance increase. This is caused by the peak position of amount of deposited sputtering atom on the substrate change by the TT distance.

DOI： 10.1109/MHS.2014.7006100

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Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人 日本機械学会  

DOI： 10.1299/jsmemag.118.1161_468_2

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

A thin-film thermoelectric generator with anti-reflection structures was fabricated to convert near-infrared solar light, which cannot be converted to electric energy by photovoltaic conversion, to electric energy. The anti-reflection structures were designed using Rigorous Coupled Wave Analysis, resulting that the anti-reflection structures which were formed by close-packed SiO_2 microspheres with 200 nm diameter and coated with CuO thin films estimated to be 6.7%. The anti-reflection structures were formed onto the SiO_2 glass substrate by dip coating method. When the SiO_2 microspheres were dispersed into deionized water and amphiphilic block copolymer F-127, the hexagonally close-packed microspheres were formed on the substrate by dip coating. Bi_<0.5>Sb_<1.5>Te_3 (p-type) and Bi_2Te_<2.7>Se_<0.3> (n-type) thin film elements were formed onto the glass substrate by lithography and sputtering method and serially connected by Cu thin films. After SiO_2 thin-film over-coating the thermoelectric elements, CuO-based anti-reflection structures were successfully formed onto the hot side of the generators.

DOI： 10.1299/jsmemnm.2015.7._28pm3-f-7

CiNii Research

Language：English   Publisher：The Japan Society of Mechanical Engineers  

Magnetostrictive materials of the Fe-Ni-Cr ternary system for sensitivity enhancement of force sensors were searched by using a combinatorial method. Magnetostrictive materials for force sensors require large magnetostriction, high relative permeability, and high resistivity. This research is an attempt to find composition ranges that satisfy the following requirements: magnetostriction greater than 20×10 ^-6, relative permeability greater than 4,000, and resistivity over 90 μΩ cm. A novel combinatorial deposition method, known as Combinatorial New Facing Targets Sputtering (Combi-NFTS) method was applied to fabricate libraries of samples with various compositions. Samples for measurement of the relative permeability and resistivity were synthesized with a composition distribution by using Combi-NFTS onto a 108 mm×76 mm glass substrate. After deposition of thin film, each sample is divided into 10 mm×10 mm. The relative permeability and resistivity were measured by using a vibrating sample magnetometer and the four probe method, respectively. Bilayer cantilever samples for evaluation of magnetostriction were fabricated onto a 6 mm×20 mm×0.1 mm Si substrate, whereby deflection of the samples changes when a magnetic field is applied. The laser lever method was used to measure the cantilever deflection. The results indicate that the composition range with an Fe content of 26-36.5 at.%, a Ni content of 61-66 at.%, and a Cr content of 7.5-9.5 at.% satisfy the requirement criteria.

DOI： 10.1299/mej.14-00462

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Micro-temperature sensors consisting of Cu_2O-rich sensing part and Cu-rich electrodes were fabricated using femtosecond laser induced reduction of CuO nanoparticles. Cu_2O-rich and Cu-rich microstructures were selectively formed by controlling laser irradiation conditions. When the laser scanning pitch was 10 μm, Cu_2O-rich microstructures were formed under the condition that the laser scanning speed and pulse energy were 1 mm/s and 0.45 nJ, respectively. Cu-rich microstructures were fabricated by the scanning speed of 10 mm/s and the pulse energy of 0.28 nJ. The Cu_2O-rich sensing part and Cu-rich electrodes were formed using the evaluated conditions. The micro-temperature sensors composed of Cu_2O-rich and Cu-rich hybrid structures were successfully obtained.

DOI： 10.1299/jsmemnm.2015.7._29pm1-b-4

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In this paper, we investigated characteristics of Ti-Ni-Cu thin film metallic glasses (TFMGs)/ shape memory alloys (SMAs) for MEMS application with three dimensional structure. The Ti-poor Ti-Ni-Cu amorphous thin films (Ti content of less than 50 at.% and Cu content of more than 6 at.%) exhibited glass transition during crystallization proces and were TFMGs. Moreover, a little Ti-rich Ti-Ni-Cu (Ti-content of less than 51 at.%) samples also showed the glass transition. On the other hands when Ti content was more than 51 at.%, these samples didn't show the glass transition, irrespective of Cu content. Therefore, it is considered that the glass forming ability of Ti-Ni-Cu TFMG was better than that of the Ti-Ni-Zr TFMGs. The Ti-Ni-Cu TFMGs after crystallization at 973 K for 3.6ks showed the single martensitic transformation of B2-B19 phase upon cooling and heating. When Ti content was around 50 at.%, peak temperatures of martensitic transformation O* and A* increased with increasing Cu content until 16 at.%. Further Cu content increasing, O* and A* decreased.

DOI： 10.1299/jsmemecj.2015._j2220101-

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

We proposed fabrication process of nickel (Ni) microstructures using femtosecond laser reduction of NiO nanoparticles (NPs), and evaluated patterning properties of the Ni microstructures. In this process, NiO NP solution was prepared by mixing NiO NPs, ethylene glycol as a reducing agent, and polyvinylpyrrolidone. Then, NiO NP solution film, which was obtained by spin-coating of the NiO NP solution, was irradiated by femtosecond laser pulses in the air. As a result, NiO NPs were reduced to form Ni microstructures using thermal reaction induced by the laser irradiation. When the pulse energy was as low as 0.24 nJ, the line width was constant to be approximately 10-15 μm without depending on the laser scanning speed. This small and constant line pattern is advantageous for high resolution patterning. Crystal structure of the micropatterns was evaluated using XRD (X-ray diffraction). Maximal ratio of the XRD peak intensity of Ni to NiO was obtained under the condition that scanning speed was 1200 μm/s at pulse energy of 0.24 nJ. Using this laser irradiation condition, Ni microgear was formed. The thickness of Ni microgear was approximate 10 μm as almost equal to the NiO NP film by Field Emission Scanning Electron microscope observation. The Ni microgear enabled to be controlled by external magnetic field.

DOI： 10.1299/jsmemecj.2015._s0440103-

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Electrical conductivity and temperature characteristic of resistance of Cu micropatterns which were fabricated by femtosecond laser induced thermal reduction of CuO nanoparticles (NPs) was investigated. The Cu micropatterns were obtained by femtosecond laser irradiation of CuO NPs film which included CuO NPs, ethylene glycol as a reduction agent and polyvinylpyrrolidone. Composition ratio of Cu and Cu_2O of the micropatterns was evaluated by comparison of Cu/CuO and Cu_2O/CuO principal peak intensity ratios of X-ray diffraction spectra. When the scanning speed was 500 μm/s and pulse energy was 1.2 nJ, the most Cu-rich micropatterns were achieved. Besides, the temperature dependence of the resistance of Cu- and Cu_2O-rich micropatterns were evaluated. The resistance of the Cu- and Cu_2O-rich micropatterns were respectively increased and decreased with the increase of the temperature. The temperature coefficients of resistance of Cu- and Cu_2O-rich micropatterns were approximately 1.0×10^<-3>/℃ and -1.5×10^<-2>/℃, respectively. These results suggest that Cu- and Cu_2O-rich micropatterns have semiconductor and metal temperature characteristics of the resistance. This higher sensitivity of Cu_2O-rich micropatterns can be applied for micro-temperature sensors effectively.

DOI： 10.1299/jsmemecj.2015._s0440102-

CiNii Research

Language：English   Publisher：The Japan Society of Mechanical Engineers  

We investigated characteristics of Ti-Ni-Zr thin film metallic glasses (TFMGs). The Ti-Ni-Zr amorphous thin films having Ni-content of more than 50 at.% and Zr-content of more than 11 at.% exhibited glass transition. Although the Ti_<39> Ni_<50> Zr_<11> sample had alloy composition at the boundary between TFMG and only amorphous, it showed the lowest glass transition temperature T_g of 703 K and wide width of supercooled liquid region (SCLR) ΔT of 57 K. Moreover, this sample showed a high thermal stability at the T_g . However, it is considered that viscosity of this sample was higher than those of other TFMGs

DOI： 10.1299/jsmemipe.2015._mob-2-1-1

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

We proposed a microvalve using photoprocessible thremoresponsible gel, which is called "Bioresist". Bioresist has characteristic of shrinking higher than 32 degree Celsius and swelling lower than 32 degrees. The volum change is utilized for opening and closing the microvalve. Since Bioresist is patterned, we can fabricate any arbitrary 2D shape of Bioresist using photolithography. We developed a microvalve which can control opening and closing by integrating the patterned Bioresist with a microheater using MEMS technology. The microvalve using Bioresist hasthe advantage of high speed response and low power consumption. We evaluated the relationship between applied current required for opening the microvalve and flow rate when microvalve were tested under regular pressurized flow with de-ionized (DI) water. As a result, flow rate is proportional relationship with applied current. It was shown controllability of flow rate by applied current.

DOI： 10.1299/jsmemecj.2015._j2220305-

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Lubricating oil is widely used to improve performance and life of various machines. However, when amount of moisture in lubricating oil increase, lubrication performance of the lubricating oil deteriorate. It cause the trouble of the machine. Therefore, the sensor to monitor amount of moisture in lubricating oil is need. This research propose capacitance type moisture sensor that can measure the relative humidity of lubricating oil in the real time. Dielectric constant changes by moisture absorption of the dielectric of the sensor. Relative humidity can be monitored by detecting changes of capacitance. So, it is need that electrode of capacior has porous structure to facilitate moisture absorption of dielectric. In the paper, this electrode was deposited by oblique angle sputtering in high sputtering gas pressure. We defined incidence angle of sputtering particle. And we fabricated three kinds of sensors whose incidence angles of sputtering particle were respectively 90, 60, 30 degrees. Those sensors were evaluated for the relative humidity in the atmosphere using temperature and humidity testing chamber. As incidence angle decreased, hysteresis decreased. (90 deg.:12.2%F.S., 60 deg.:10.1%F.S., 30 deg.:7.2%F.S.) We considered the reason of this decrease of the hysteresis is that porosity of the electrode increased because shadow effect became remarkable.

DOI： 10.1299/jsmemecj.2015._j2220302-

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Thermal-photovoltaic hybrid solar generators is one candidate for energy harvesting devices. Near-infrared solar light which cannot be used for photovoltaic generator is used for thermoelectric generator. Hybrid generator with buls lens to generate temeperature gradient has been fabricated. However, it is difficult to reduce the volume of the generators due to the bulk lens. In our study, we proposed a thin-film thermoelectric generator with anti-reflection structures on the hot side of pn junctions. First, we designed the anti-reflection structures using rigorous coupled wave analysis. When the grating period was 200 nm, the reflectance exhibits minimal value of 6.7%. Anti-reflection structures was fabricated using self-assembled silica microspheres and following CuO thin film deposition. The silica microspheres were assembled by dip coating. Then, the CuO thin film were coated by reactive sputtering on the self-assembled microspheres to reduce the energy loss and to convert the solar light to thermal energy. Finally, we investigated the effect of the ant-reflection structures using a commercially-available bulk thermoelectric module. The generation voltage of the modules with anti-reflection structures was increased by comparing to the modules without the structures. This result indicates that the near-infrared solar light was efficiently absorbed and converted to the thermal energy by anti-reflection structures.

DOI： 10.1299/jsmemecj.2015._j2220201-

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Electrode catalyst used in industrial electrolysis is important material which affects oxidation-reduction reaction materially. The electrode catalyst having high catalystic activity and high durability gives efficient production of chemical materials. In this study, we proposed to search for new electrode catalyst using a combinatorial method. The evaluation substrate consisting of 72 catalyst samples and 9 Pt reference electrodes was designed and fabricated by a micro electro mechanical system (MEMS) technique. The thin film electrode catalyst library on the evaluation substrate was prepared by a combinatorial multi target sputtering system using 3 pure metal targets (Ir, Ru and Ti). The alloy compositions of these thin films were measured by an energy dispersive X-ray spectroscopy. To evaluation the characteristics of catalyst samples, the polarization curves (current density/potential curves) of catalyst samples were measured by the potential sweep method. Surface poisoning and elution of catalysis samples were observed by an optical microscopy. Finally, we confirmed that the proposed combinatorial method was useful to search for new electrode catalyst materials.

DOI： 10.1299/jsmemecj.2015._j2220105-

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Magnetostrictive materials often used for several sensors and actuators from some features that are fast response, high power, and contactless actuation. Magnetostriction and relative permeability are important characteristics to determine the performance of the sensors and actuator, however, it need the different sample to evaluate magnetostriction and relative permeability. So that, it takes a lot of time to search new magnetostrictive materials or optimize composition of alloy magnetostrictive materials. The combinatorial method could search novel alloy materials or optimize composition efficiently compared to the conventional material searching method. In this research, we proposd the MEMS device for the combinatorial materials searching method. This device could evaluate characteristics of magnetostrictive material that are magnetostriction and relative permeability. Moreover, magnetostriction an drelative permeability are evaluated by the change of capacitance, induced electromotive force, respectively. In this paper, we show the fabrication process and fabricated device that keeps the cantilever structure.

DOI： 10.1299/jsmemecj.2015._j2220102-

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DOI： 10.1016/j.actaastro.2014.10.020

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DOI： 10.1002/ecj.11681

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We have demonstrated a patterning process for the fabrication of thermoelectric thick-film modules by a thermally assisted sputtering method (TASM) and a lift-off technique. Given the experimental requirements of TASM, poly(dimethylsiloxane) (PDMS) was used as the heat-resistant masks in the lift-off technique. After the film deposition, the PDMS lift-off mask was removed from the substrate. This process enables the fabrication of 30-mu m-thick and 300-mu m-wide Sb2Te3 and Bi2Te3 thick-film patterns. The increase in film thickness increased the power generated by the module, which was consistent with the theoretical value. (C) 2014 The Japan Society of Applied Physics

DOI： 10.7567/APEX.7.057101

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Mold materials for glass lenses with microstructures, such as gratings, require not only excellent mechanical properties, high thermal stability and oxidation resistance, but also sufficient machinability by Single-Point Diamond Turning (SPDT). Our research on Ni-Nb-Zr alloys has shown that one amorphous alloy composition (Ni35Nb40Zr25 at.%) met almost all the requirements for glass lens mold materials. Unfortunately, when fabricating gratings on the mold, the immense wear on the bit, which may be caused by the high hardness of the alloy (more than 10 GPa by the nano-indentation method), made it impossible to cut precise gratings. Consequently, the addition of a fourth element was considered to decrease the hardness. After several experiments, the addition of Ti was found to decrease the hardness. At first, Ti was added to substitute 10% Zr, to give Ni35Nb40Zr15Ti10 at.%. Although this alloy had a lower hardness (9.5 GPa) than Ni35Nb40Zr25 at.%, it still cannot be micro-cut by SPDT. It was then decided to substitute Ti for Ni-Nb instead of Zr. Three samples: Ni30Nb35Zr25Ti10 at.%, Ni28Nb32Zr25Ti15 at.% and Ni25Nb30Zr25Ti20 at.%, were fabricated for evaluation. Finally, the Ni28Nb32Zr25Ti15 at.% and Ni25Nb30Zr25Ti20 at.% were found to have a low enough hardness to allow for precision machining. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.mee.2013.11.008

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Publisher：2014 International Symposium on Micro-NanoMechatronics and Human Science, MHS 2014  

Copper oxide anti-reflection structures were designed by rigorous coupled wave analysis for thin-film thermoelectric solar generator. We proposed thin-film thermoelectric generator with the anti-reflection structure on the hot side of pn junction. When infrared solar light from 800 to 1200 nm wavelength is irradiated to the thermoelectric generator, the anti-reflection structure on the hot side generates the temperature gradient between the hot side and cold side of pn junction. When the cross-sectional geometry of the anti-reflection structures was hemisphere which was geometrically approximated pyramid one, the reflectance from 800 to 1200 nm wavelength was reduced than flat and binary ones. The reflectance of solar light was obtained by considering the solar light spectra and its polarization. By assuming that the average of TM and TE polarized light was the reflectance of solar light, the reflectance was reduced to be 9.6% when the period of the anti-reflection structure was 700 nm. Taking into account of the reflectance of Cu on cold side 99%, this large reflectance difference is expected to generate a large temperature gradient between hot side and cold side.

DOI： 10.1109/MHS.2014.7006118

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Copper oxide anti-reflection structures were designed by rigorous coupled wave analysis for thin-film thermoelectric solar generator. We proposed thin-film thermoelectric generator with the anti-reflection structure on the hot side of pn junction. When infrared solar light from 800 to 1200 nm wavelength is irradiated to the thermoelectric generator, the anti-reflection structure on the hot side generates the temperature gradient between the hot side and cold side of pn junction. When the cross-sectional geometry of the anti-reflection structures was hemisphere which was geometrically approximated pyramid one, the reflectance from 800 to 1200 nm wavelength was reduced than flat and binary ones. The reflectance of solar light was obtained by considering the solar light spectra and its polarization. By assuming that the average of TM and TE polarized light was the reflectance of solar light, the reflectance was reduced to be 9.6% when the period of the anti-reflection structure was 700 nm. Taking into account of the reflectance of Cu on cold side 99%, this large reflectance difference is expected to generate a large temperature gradient between hot side and cold side.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

When suitable materials in the right place are able to place freely anywhere, it can be produced with microactuators, sensors, and signal processing circuit to freely also inside as well as the surface of mechanical parts. Although they are basic research, two new processes indicating the possibility are introduced in this presentation. One is novel lift-off process using die. The other is direct reduction Cu patterning process by femtosecond laser pulses. These new processes show the potential to allow any arrangement of a polymeric material and metal in any place.

DOI： 10.1299/jsmemecj.2014._f041003-1

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In Micro Electro Mechanical Systems (MEMS) technology, structure of amorphous alloy thin film is manufactured by sputter deposition and lift-off process. But its thickness is not uniform because lift-off masking material block off. The structure thickness of amorphous alloy thin film is low in the vicinity of lift-off masking material, and its cross-sectional shape is not rectangular. For these problems, we proposed new fabrication method of thick film structure of metallic glass with the sputtering jig, which combines projection surfaces and spacers. As this application, we have successfully fabricated two-axis scanning micro mirror device with thin film metallic glass Cu-Zr-Ti, which have uniform film thickness, rectangular cross-sectional shape and electrical factors. However, the sample was not able to be driven in driving test, because the torsion bar of sample had been broken for Cu-Zr-Ti crystallization. In this paper, we proposed low temperature production process which is not to crystallize Cu-Zr-Ti. And we have succeeded in fabricating and driving the two-axis scanning micro mirror device.

DOI： 10.1299/jsmemecj.2014._j2220102-

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

CuO nanoparticles were directly reduced to form fine Cu micropatterns using femtosecond laser pulses. CuO nanoparticles were dispersed into reductant agent and base-polymers. When the focused laser pulses were irradiated into the CuO nanoparticle based films on glass substrates, the Cu micropatterns were formed by reducing and sintering of CuO nanoparticles. XRD spectrum of the laser irradiated areas shows Cu peaks although the Cu peaks were not observed in XRD spectra of the non-irradiated area. The width of the Cu micropatterns were increased by decreasing laser pulse energy and increasing laser scanning speed. The minimum line width was 7 μm under the condition that the laser pulse energy and scanning speed were 0.36 nJ and 100 μm/s, respectively. When the pulse energy was low and the scanning speed was high, the line width of the Cu micropatterns only depended on the pulse energy, not the scanning speed. This result indicates that the threshold fluence could exist to form Cu micropatterns.

DOI： 10.1299/jsmemecj.2014._s0440101-

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Performance of lubricating oil gets worse suddenly by water being mixed into oil. This causes serious failure of machine. Therefore, a sensor that monitors amount of moisture in the oil is need. In this paper, capacitance type moisture sensor is proposed for the use in lubricating oil. To realization of the sensor, upper electrode Cr was deposited as nanocrack thin film metal that separates water molecules from oil by sputtering in high sputtering gas pressure and diagonal incidence of sputtering particle. Evaluation of the sensor was conducted in the air as previous stage of evaluation in oil. The sensor proposed in this paper showed followabillity for amount of moisture in the air. Relation between sensor characteristic and sputtering condition was investigated.

DOI： 10.1299/jsmemecj.2014._j2220203-

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In this research, it was searched that magnetostrictive materials for sensors by using combinatorial method. Combinatorial method is the one of the useful method that could search for optical composition of alloy materials or novel alloy materials. In this method, samples having various compositions are synthesized onto a single substrate. Then, properties of each sample are evaluated efficiently. Desired value of this research is that, magnetostriction is more than 20×10^<-6>, relative permeability is more than 4000, resistivity is more than 90 μΩ・cm. Library to evaluate resistivity and relative permeability which has composition distribution was synthesized by using New Facing Targets Sputtering. Resistivity of as-sputtered sample was evaluated by using four probe method and relative permeability of annealed sample was evaluated by using vibrating sample magnetometer. Magnetostriction of annealed sample was relatively evaluated comparing to reference material. As the result, it was discovered composition area that satisfied all targeted value.

DOI： 10.1299/jsmemecj.2014._j2220202-

CiNii Research

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we proposed a new fabrication method of thick film structure which has rectangular cross-sectional shape. This fabrication method utilized a new sputtering jig consisting of substrate and spacer units. The surface level of spacer unit is lower than one of substrate unit. After thick film deposition, the spacer unit is removed. In comparison with conventional sputtering and lift off process, thickness uniformity of structure fabricated by this method is improved dramatically. Finally, we fabricated the two-axis scanning micro mirror device which has coil element on the thick film structure of Parylene-C/Cu-Zr-Ti thin film metallic glass. This device achieved the optical scan angles of horizontal 10 degrees and vertical 10 degrees.

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Language：English  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

This paper suggests a poly(vinylidene fluoride) (PVDF) piezoelectric diaphragm actuator used in a novel fatigue test method for thin metal films. A thin-film metal specimen is stamped on top of the actuator using a stamping epoxy. As the actuator vibrates, the stress in the specimen increases until it fails under fatigue. A finite element model of the actuator is built, and its vibration amplitude is confirmed to be in a good agreement with experiment. Then, a model of the specimen is added to this model to simulate the vibration of the specimen for fatigue test. Stress analysis of the specimen at a driving voltage of 200 V0p confirms that this actuator can increase the stress in the specimen to near 1 GPa, which is high enough for the fatigue test of metals such as titanium. In the experiment, a thin-film titanium specimen is stamped on top of the actuator which is then vibrated. The stress in the fatigue gauge on thin-film specimen increased until the specimen failed under fatigue. This shows that the proposed PVDF actuator is suitable for the fatigue test of thin-film metals such as titanium. (c) 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

DOI： 10.1002/tee.21840

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electrical Engineers of Japan  

Combinatorial search is one of the useful methods that could search for optimal composition of alloy materials or novel alloy materials. Combinatorial sputtering provides sample group (library) having different compositions in a limited place. Then, the properties of the samples can be scanned in an efficient way. In this research, it was studied that magnetostrictive material with high magnetostriction, relative permeability and resistivity. Desired value of magnetostriction is more than 20×10^-6, relative permeability is more than 4000, and resistivity is more than 100 µΩ·cm. As a result, composition that Cr content is less than 14 at.% fill the desired value of relative permeability, and more than 10 at.% fill the desired value of resistivity. There is possibility to fill the desired value of magnetostriction.

DOI： 10.1541/ieejsmas.133.342

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electrical Engineers of Japan  

Thin film shape memory alloys (SMAs) are promising materials for micro-machines because of their high-output power, large strain, and actuation without high voltage. To search for compositions of suitable thin film SMAs for each application, combinatorial technique is useful tool, however the technique requires high-throughput characterization method for thermal property which is an important property of thin film SMAs such as two way martensitic transformation temperature and thermal hysteresis. In this paper, novel high-throughput characterization method for such properties using thermography is proposed and demonstrated. Compositionally integrated thin film SMA samples (TiNiPd) with only 1mm² of each area are characterized at once. The difference of martensitic and reverse martensitic transformation temperature against those temperatures measured by a conventional method, differential scanning calorimetry, is about 5K.

DOI： 10.1541/ieejsmas.133.348

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Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (other academic)   Publisher：一般社団法人 電気学会  

DOI： 10.1541/ieejsmas.133.nl6_2

CiNii Research

Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人 日本機械学会  

DOI： 10.1299/jsmemag.116.1137_534_2

CiNii Research

Language：English   Publisher：The Japan Society of Mechanical Engineers  

Abstract As mold material for glass lens with microstructures, it requires not only excellent mechanical properties, high thermal stability and oxidation resistance, but also satisfying machinability Using combinatorial arc plasma deposition, Ni-Nb-Ti thin film libraries were deposited for evaluations of some properties, such as, crystallization temperature, thermal stabilities, hardness, oxidation resistance and so on When Ni within 40-58 at %, Nb within 24-46 at %, Ti within 5-20 at %, the thin film exhibited excellent thermal stability However, for machinability, the conventional method can measure only one composition at each time which is both time-consuming and expensive Therefore, a novel combinatorial deposition and evaluation method for machinability are proposed In those methods, thin film samples with concentrically grading composition are sputter - deposited using combination targets The sample has grading compositions of which in the center Ti content is rich and becomes gradually decreasing from center to edge This means that each position on the surface of sample represents a particular composition Then this sample will be cut at different positions After that, cutting depth and the roughness of cutting surfaces will be measured It is clearly to see this new method is more efficient than conventional method, which is able to measure a lot of compositions' machinability at one time with one sample

DOI： 10.1299/jsmemp.2013.21._632-1_

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In MEMS technology, it is important to know the characteristics of thin film alloys. Studies have been made on the high speed and high efficiency high-throughput evaluation in a wide variety of samples. Nevertheless, high-throughput evaluation of fatigue strength which is important in MEMS design has not been studied enough. In this research, we propose a high-throughput fatigue test for thin film alloys using micro-actuator, including the fabrication of both micro-actuator and specimen. This method is succeeded applying on Ti specimen with higher than 5 kHz frequency of loading. Finally, the S-N curve of Ti thin film was obtained.

DOI： 10.1299/jsmemecj.2013._j212017-1

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Combinatorial search is one of the useful methods that could search for optimal composition of alloy materials or novel alloy materials. Combinatorial sputtering provides sample group (library) having different compositions in a limited place. Then, the properties of the samples can be scanned in an efficient way. In this research, it was studied that magnetostrictive material with high magnetostriction, relative permeability and resistivity. Desired value of magnetostriction is more than 20×10^<-6>, relative permeability is more than 4000, and resistivity is more than 100 μΩ・cm. As a result, composition that Cr content is less than 14 at.% fill the desired value of relative permeability, and more than 10 at.% fill the desired value of resistivity. Magnetostriction was evaluated by the capacitance change of capacitor consisted of cantilever and electrode.

DOI： 10.1299/jsmemecj.2013._j212012-1

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper introduces driven methods for curled-up type electrostatic micro actuator made of thin film metallic glasses. One of the methods achieves analog motion over the full range of its stroke without closed loop control system. The device consists of a curled-up moving electrode that delivers large deflection in the out-of-plane direction and a taper-shaped base electrode. A prototype device achieves analog motion for 70% by rectangular AC voltage from 0V to 400V. Another method removes remnant charge that can cause a moving electrode to "stick" to its insulator and demonstrates the effectiveness of the method experimentally. The method is applicable to many types of MEMS because it does not require any change to the actuator fabrication process, structure, dimensions or materials. The only modification is to the waveform of the applied voltage.

DOI： 10.1299/jsmemecj.2013._f113004-1

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In Micro Electro Mechanical Systems (MEMS) technology, thick film structure is manufactured by sputter deposition and lift-off process. However, its thickness is not uniform because lift-off masking material block off. The structure thickness is low in the vicinity of lift-off masking material, and its cross-sectional shape is not rectangular. Thick film structure design is limited by this problem. Furthermore, it is hard to build uniformly electrical factors on the thick film structure surface. In this paper, we propose compound micro process for thick film structure with the sputtering jig, which combines projection surfaces and spacers. In the new compound micro process, since thick film structure is formed on the projection plane, the film thickness does not decrease as compared with lift-off process. Thereby, electrical factors can be built on the thick film structure surface. That structure is separated from the sputtering jig by removal of sacrificial layers and pacers. By removing the extra burr, thick film structure that has rectangular cross section and uniform thickness is made. In this way, we have successfully fabricated two-axis scanning micro mirror device with thin film metallic glass Cu-Zr-Ti, which have uniform film thickness, rectangular cross-sectional shape and electrical factors.

DOI： 10.1299/jsmemecj.2013._j212021-1

CiNii Research

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

To realize a sensor that monitors moisture-in-oil, it is required a nanoporous thin film to separate water moleculars from oil. In this paper, we propose nanoporous thin films by utilizing dealloying behavior of dual-phase alloy in an acidic solution. Dealloying behavior is selective chemical etching process some of the most intricate and random three-dimensional morphologies. Using this dealloyed nanoporous thin film as an upper electrode of sensor, we produce a moisture-in-oil sensor that has an outstanding resistance for environment. Nanoporous Cr thin films were prepared by sputtering Cu and Cr, followed by annealing and dealloying. The nanoporous Cr thin films had pores ranging from about 200 nm to 300 nm and thicknesses about 1.0 μm.

DOI： 10.1299/jsmemecj.2013._j212036-1

CiNii Research

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmemag.116.1130_11

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Publisher：Materials Research Society Symposium Proceedings  

Combinatorial sputtering is one of the useful methods that can be used to search for optimal composition of alloy materials or for new alloy materials. To search materials more efficiently, it is required that compositions and their distribution on samples can be easily controlled for the evaluation of their properties. Moreover, it is desirable that compositions change linearly to search for novel materials systematically. In conventional combinatorial sputtering method, it is difficult to fabricate samples having linear compositions distribution without moving hard masks or rotating substrate. In this paper, a novel combinatorial sputtering method with New Facing Targets Sputtering (Combi-NFTS) of material search is introduced. In this method, several sputtering targets are placed in opposite direction, and substrates are placed in vertical direction of these targets. From this structure, thin film with binary/ternary composition distribution could be synthesized onto one single substrate. Moreover, it can fabricate samples having relatively linear composition distribution without moving hard masks or rotating substrate. As an example, Cu, Zr and Ti pure targets were used to confirm the performance of Combi-NFTS. Binary system of Cu-Zr and ternary system of Cu-Zr-Ti thin films were fabricated by using Combi-NFTS. After deposition, compositions of the films were characterized by the energy dispersive X-ray spectroscopy. As a result of Cu-Zr binary system, the composition of the thin film was changed as the power of targets was changed. Moreover, composition distribution was expanded as the distance from substrate to targets was decreased. In the Cu-Zr-Ti ternary system, it was obtained similar trend for composition distribution. Moreover, the composition changed two dimensional by changing the substrate position. These results indicate that combi-NFTS can easily control the composition and composition distribution of thin films by changing the power of targets or the distance from substrate to targets which make combi-NFTS very suitable for combinatorial materials search. © 2012 Materials Research Society.

DOI： 10.1557/opl.2012.1403

Scopus

Language：English   Publisher：ELSEVIER SCIENCE SA  

We conducted a search for Ti-Ni-Zr thin film metallic glasses (TFMGs) exhibiting a shape memory effect after crystallization. We investigated the possibility of (Ti, Zr)((100-x))-Ni-x thin film amorphous alloys exhibiting a glass transition. All prepared samples were classified into three groups such as Ti-rich (x &lt; 50). equiatomic (50 &lt; x &lt; 51)and Ni-rich (x &gt; 51) samples. Equiatomic Ti-Ni-Zr thin film amorphous alloys with Zr content ranging from 11 to 17 at.% showed a glass transition, and thus were concluded to be TFMGs. Several Ni-rich samples exhibit glass transition and were also TFMGs. On the other hand, Ti-rich samples did not exhibit a glass transition irrespective of the Zr content. Moreover, we investigated the shape memory behavior of crystallized TiNiZrTFMGs. Ti39Ni50Zr11 TFMGs annealed at 973 K for 3.6 ks exhibited a martensitic transformation from the B2 to the B19' phase upon cooling and heating. The martensitic phase start temperature and reverse martensitic phase start temperature were 296 and 352 K, respectively. In addition, this alloy showed good shape memory behavior, achieving recovery strain of 2.5% and a critical stress for slip of 500 MPa. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.msea.2012.01.075

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Language：English   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Novel high-frequency bending fatigue test method for sputtered metallic thin films using PVDF microactuator is proposed. Thin film titanium specimen as an example and a PVDF piezoelectric microactuator are fabricated. The specimen is stamped on this actuator and the actuator is vibrated at its resonance frequency until the specimen fails by fatigue. The stress in the specimen is calculated from vibration amplitude. By using the proposed method, the stress-fatigue life cycle (S-N) curve of the thin film titanium is obtained over 50 times faster than conventional method.

DOI： 10.1587/elex.9.403

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DOI： 10.1109

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DOI： 10.1299/jmmp.4.1742

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DOI： 10.1088/0964-1726/19/4/045008

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DOI： 10.4172/2321-6212.1000155

Language：English   Publishing type：Research paper, summary (national, other academic conference)  

A flexible thermoelectric generator with a lens array that converts near-infrared (NIR) solar light, was fabricated using lithography and thin-film deposition processes. The generator comprised serially connected 270 pairs of thin-film thermocouples and a polydimethylsiloxane (PDMS) lens array. It possessed the flexibility to be easily placed on glass windows. The thermoelectric elements of Cu (p-type) and Cu-Ni (n-type) thin films were used in thermoelectric generators. The thermoelectric thin films were deposited on flexible polyimide substrates using sputtering method and were formed using lift-off techniques. When solar light (A.M. 1.5) was irradiated onto the fabricated generator, the open-circuit voltage and the maximum power were 7.4 V/m2 and 11 μW/m2 respectively. The flexible thermoelectric generator can be placed on arbitral hard materials, such as glass windows, for energy harvesting.

DOI： 10.1109/MEMSYS.2018.8346626

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Language：English   Publisher：CAMBRIDGE UNIV PRESS  

DOI： 10.1557/adv.2018.492

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Language：Japanese   Publisher：Institute of Electrical Engineers of Japan  

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Language：Japanese   Publisher：Institute of Electrical Engineers of Japan  

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Language：Japanese   Publisher：電気学会  

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Language：English   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

DOI： 10.4172/2321-6212.1000155

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Language：Japanese   Publisher：Institute of Electrical Engineers of Japan  

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Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)  

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Micro-temperature sensors, which composed of a Cu2O-rich sensing part and two Cu-rich electrodes, were directly fabricated by femtosecond<br />
laser reduction patterning of CuO nanoparticles. Patterning of the microstructures was performed by laser scanning with pitches of 5, 10, and<br />
15 µm. Cu2O-rich micropatterns were formed at the laser scan speed of 1 mm/s, the pitch of 5 µm, and the pulse energy of 0.54 nJ. Cu-rich<br />
micropatterns that had high generation selectivity of Cu against Cu2O were fabricated at the laser scan speed of 15 mm/s, the pitch of 5 µm, and<br />
the pulse energy of 0.45 nJ. Electrical resistivities of the Cu2O- and Cu-rich micropatterns were approximately 10 Ω m and 9 µΩ m, respectively. The<br />
temperature coefficient of the resistance of the micro-temperature sensor fabricated under these laser irradiation conditions was %5.5 &#039; 10%3/°C.<br />
This resistance property with a negative value was consistent with that of semiconductor Cu2O. © 2016 The Japan Society of Applied Physics

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Language：Japanese   Publisher：Institute of Electrical Engineers of Japan  

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Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Japan Society of Mechanical Engineers  

A thin-film thermoelectric generator with anti-reflection structures was fabricated to convert near-infrared solar light, which cannot be converted to electric energy by photovoltaic conversion, to electric energy. The anti-reflection structures were designed using Rigorous Coupled Wave Analysis, resulting that the anti-reflection structures which were formed by close-packed SiO_2 microspheres with 200 nm diameter and coated with CuO thin films estimated to be 6.7%. The anti-reflection structures were formed onto the SiO_2 glass substrate by dip coating method. When the SiO_2 microspheres were dispersed into deionized water and amphiphilic block copolymer F-127, the hexagonally close-packed microspheres were formed on the substrate by dip coating. Bi_<0.5>Sb_<1.5>Te_3 (p-type) and Bi_2Te_<2.7>Se_<0.3> (n-type) thin film elements were formed onto the glass substrate by lithography and sputtering method and serially connected by Cu thin films. After SiO_2 thin-film over-coating the thermoelectric elements, CuO-based anti-reflection structures were successfully formed onto the hot side of the generators.

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Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Japan Society of Mechanical Engineers  

Micro-temperature sensors consisting of Cu_2O-rich sensing part and Cu-rich electrodes were fabricated using femtosecond laser induced reduction of CuO nanoparticles. Cu_2O-rich and Cu-rich microstructures were selectively formed by controlling laser irradiation conditions. When the laser scanning pitch was 10 μm, Cu_2O-rich microstructures were formed under the condition that the laser scanning speed and pulse energy were 1 mm/s and 0.45 nJ, respectively. Cu-rich microstructures were fabricated by the scanning speed of 10 mm/s and the pulse energy of 0.28 nJ. The Cu_2O-rich sensing part and Cu-rich electrodes were formed using the evaluated conditions. The micro-temperature sensors composed of Cu_2O-rich and Cu-rich hybrid structures were successfully obtained.

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

In Micro Electro Mechanical Systems (MEMS) technology, a lift-off process with sputter deposition is one general patterning method for amorphous alloy thick film structure. However, a thickness of the structure is not uniform because sputtered particles are hindered by side a wall of the lift-off layer. In this paper, a new patterning method of amorphous alloy thick film structure with uniform thickness was proposed. Moreover, this patterning method was defined as "Reversed lift-off process". In reversed lift-off process, convex parts with the desired structure shape is formed on a top of a substrate. Thick film structure is deposited by the sputter deposition on the top surface of convex parts. A thickness of the structure is uniform because there is nothing which hinders sputtered particles in contrast to a conventional lift-off process. As a practical experiment of reversed lift-off process, we successfully fabricated Cu-Zr-Ti metallic glass thick film structure which has uniform film thickness, rectangular cross-sectional shape, and noncrystalline in a different width of the structure. Moreover, it was confirmed that reversed lift-off process is suitable for the fabrication of metallic glass thick film structure in the comparison with the conventional lift-off process.

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Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Japan Society of Mechanical Engineers  

CuO nanoparticles were directly reduced to form Cu micropattems using femtosecond laser writing. CuO nanoparticles were dispersed into reductant agent and base polymers. When femtosecond laser pulses were focused and irradiated into the CuO nanoparticle based films on glass substrate, Cu micropattems were formed by reducing and sintering of CuO nanoparticles. X-ray diffraction spectra of the laser irradiated area shows Cu peaks although the Cup peaks were not observed in that of non-laser irradiated area. The width of the Cu micropattems was increased with decreasing laser pulse energy and scanning speed. Cu-rich patterns were obtained by laser irradiation with high laser scanning speed. The resistance of the line patterns were inversely proportional to the line width which indicated that the Cu micropattems have uniform electrical properties.

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Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Japan Society of Mechanical Engineers  

The effect of Cr or Cu buffer layers on open-circuit voltage of thin-film thermoelectric generator was investigated. Thermoelectric thin films of Bi_2Te_<2.7>Se_<0.3> (p-type) and Bi_<0.5>Sb_<1.5>Te_3 (n-type) were deposited onto SiO_2 glass substrate using the Cr or Cu buffer layers. The buffer layer enabled to prevent the thermoelectric thin films from removing onto the substrate during the thin-film patterning process. X-ray diffraction patterns of the thermoelectric thin films were not affected by the underlying Cr or Cu buffer layers with 1 nm thickness. The open-circuit voltage of the thin-film thermoelectric devices with 1 nm-Cr buffer layers were approximately 50 mV higher than that of the devices with 1 nm-Cu buffer layers. This value is consistent with the estimated one by taking the current flow into the buffer layers.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

When suitable materials in the right place are able to place freely anywhere, it can be produced with microactuators, sensors, and signal processing circuit to freely also inside as well as the surface of mechanical parts. Although they are basic research, two new processes indicating the possibility are introduced in this presentation. One is novel lift-off process using die. The other is direct reduction Cu patterning process by femtosecond laser pulses. These new processes show the potential to allow any arrangement of a polymeric material and metal in any place.

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Language：English   Publishing type：Research paper, summary (national, other academic conference)   Publisher：The Japan Society of Mechanical Engineers  

Abstract As mold material for glass lens with microstructures, it requires not only excellent mechanical properties, high thermal stability and oxidation resistance, but also satisfying machinability Using combinatorial arc plasma deposition, Ni-Nb-Ti thin film libraries were deposited for evaluations of some properties, such as, crystallization temperature, thermal stabilities, hardness, oxidation resistance and so on When Ni within 40-58 at %, Nb within 24-46 at %, Ti within 5-20 at %, the thin film exhibited excellent thermal stability However, for machinability, the conventional method can measure only one composition at each time which is both time-consuming and expensive Therefore, a novel combinatorial deposition and evaluation method for machinability are proposed In those methods, thin film samples with concentrically grading composition are sputter - deposited using combination targets The sample has grading compositions of which in the center Ti content is rich and becomes gradually decreasing from center to edge This means that each position on the surface of sample represents a particular composition Then this sample will be cut at different positions After that, cutting depth and the roughness of cutting surfaces will be measured It is clearly to see this new method is more efficient than conventional method, which is able to measure a lot of compositions' machinability at one time with one sample

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