Papers - OKA Chiemi

Special Issue on Medical Applications of Magnetic Nanoparticles Open Access

OKA Chiemi

Journal of the Japan Society of Applied Electromagnetics and Mechanics   Vol. 33 ( 4 ) page： 345 - 345   2026

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Applied Electromagnetics and Mechanics  

DOI： 10.14243/jsaem.33.345

Open Access

CiNii Research

Vertical ultraviolet irradiation-assisted manufacturing of unidirectional porous resin using magnetic nanoparticle chains and gas-permeable soft molds

Kobayashi, A; Sakurai, J; Hata, S; Oka, C

JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 64 ( 12 )   2025.12

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

DOI： 10.35848/1347-4065/ae2171

Web of Science

The effect of internal stress on thermal and mechanical properties of Ni-Nb-Zr thin film amorphous alloys

Xie, JL; Haga, F; Oka, C; Hata, S; Sakurai, J

JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 64 ( 7 )   2025.7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japanese Journal of Applied Physics Part 1 Regular Papers and Short Notes and Review Papers  

This study investigated the effect of initial internal stress on the thermal and mechanical properties of Ni-Nb-Zr thin film amorphous alloys (TFAAs) for MEMS devices. Samples with tensile and compressive stress and varying alloy compositions were prepared. Thermal properties were measured using differential scanning calorimetry and thermal mechanical analyzer, bulge and tensile tests assessed mechanical properties. Results showed that initial internal stress significantly influenced the β-relaxation temperature (T<inf>β</inf>), but not glass transition temperature (T<inf>g</inf>) or crystallization temperature (T<inf>x</inf>), which were dependent on alloy composition. The initial internal stress of TFAAs was almost relaxed by β-relaxation during heating. By contrast, the mechanical properties of as sputtered TFAA samples were affected significantly by the initial internal stress. However, annealing around T<inf>β</inf> diminished the initial internal stress effect. Therefore, precise control of internal stress and alloy composition is essential for optimizing the performance and reliability of Ni-Nb-Zr TFAAs in MEMS applications.

DOI： 10.35848/1347-4065/ade7df

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Scopus

Magnetic-nanoparticle-embedded "wireless" hydrogel microvalve Reviewed Open Access

Oka, C; Miwa, D; Tanihira, K; Yokoyama, Y; Sakurai, J; Hata, S

INTERNATIONAL JOURNAL OF APPLIED ELECTROMAGNETICS AND MECHANICS   Vol. 78 ( 1-3 ) page： 30 - 34   2025.7

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

DOI： 10.1177/13835416251331334

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Development of a unidirectional magnetic field-applied fast atom beam source for surface activated bonding

Oshima, K; Nomura, W; Kato, T; Oka, C; Sakurai, J; Hata, S

JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 64 ( 6 )   2025.6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japanese Journal of Applied Physics Part 1 Regular Papers and Short Notes and Review Papers  

In surface activated bonding (SAB), the surfaces of the materials to be bonded are activated by fast atom beam (FAB) irradiation in a vacuum, and then brought into contact with each other to achieve room-temperature and low-pressure bonding. The conventional FAB source used for SAB, can be used for only a short time due to bonding failures caused by carbon particle adhesion to the bonding surface. Additionally, there has been a growing need in recent years for a FAB source that can irradiate a larger area. In this study, we developed a unidirectional magnetic field-applied FAB source that can solve these problems simultaneously. The motion of charged particles in the plasma is controlled by applying magnetic fields in a unidirectional manner to the FAB source, resulting in highly efficient Ar-FAB irradiation and a reduction in the wear of the inner carbon walls caused by Ar⁺ ion sputtering.

DOI： 10.35848/1347-4065/add5af

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Scopus

Magnetic-nanoparticle-embedded “wireless” hydrogel microvalve Reviewed Open Access

Chiemi Oka, Daiki Miwa, Koichi Tanihira, Yoshiyuki Yokoyama, Junpei Sakurai, and Seiichi Hata

International Journal of Applied Electromagnetics and Mechanics     2025.4

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Authorship：Lead author,　Corresponding author  

DOI： https://doi.org/10.1177/13835416251331334

Open Access

Tuning magnetic properties by microstructure control of nanocrys­talline thin films for compact vibration energy harvesters Open Access

Sano Kohya, Yamazaki Takahiro, Nakamura Yuta, Ohtake Mitsuru, Oka Chiemi, Sakurai Junpei, Hata Seiichi

IEICE Electronics Express   Vol. 22 ( 6 ) page： 20250031 - 20250031   2025.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electronics, Information and Communication Engineers  

<p>The vibration energy harvesting properties of Fe-based nanocrystalline soft magnetostrictive material (Fe-Si-B-P-Cu-C) thin films were systematically investigated. Thin films were deposited using rotational sputtering and subsequently annealed. Nanocrystallization occurred in the samples annealed at 100-110% of the crystallization temperature. This nanocrystallization process enhanced soft magnetic properties, however, decrease saturation magnetostriction reflecting the influence of the negative magnetostrictive <i>α</i>-Fe phase. The film annealed at 105% of the crystallization temperature exhibited the highest vibration power generation performance. This superior performance was attributed to the combination of enhanced soft magnetic properties, high saturation magnetic flux density, and a relatively large saturation magnetostriction.</p>

DOI： 10.1587/elex.22.20250031

Open Access

Web of Science

Scopus

CiNii Research

4Dナノインプリントに向けた高成形性形状記憶合金マイクロ構造体の作製 Open Access

泉 光暢, 柴垣 竜資, 岡 智絵美, 秦 誠一, 櫻井 淳平

精密工学会学術講演会講演論文集   Vol. 2024A ( 0 ) page： 146 - 146   2024.8

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 精密工学会  

<p>高成形性形状記憶合金（HFSMA）は，非晶質状態で金属ガラスの特性を，結晶化後に形状記憶特性を示す．熱ナノインプリントによりHFSMA製繊毛構造体の加工を行い，ナノ繊毛アクチュエータの作製を検討している．本研究では，リソグラフィによりマイクロホールのSiモールドを作製し，熱ナノインプリントによってHFSMAマイクロ柱状構造体を作製した．今後は，高アスペクト比のナノ柱状（繊毛）構造体の作製を目指す．</p>

DOI： 10.11522/pscjspe.2024a.0_146

Open Access

CiNii Research

Effect of Noise on Accuracy of Grain Size Evaluation by Magnetic Barkhausen Noise Analysis Open Access

Omae Kanna, Yamazaki Takahiro, Sano Kohya, Oka Chiemi, Sakurai Junpei, Hata Seiichi

International Journal of Automation Technology   Vol. 18 ( 4 ) page： 528 - 536   2024.7

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

<p>Magnetic Barkhausen noise (MBN) is a magnetic signal caused by domain wall motion and is used for non-destructive testing and evaluation of ferromagnetic materials because of its sensitivity to both mechanical and magnetic properties. Recently, machine learning models have been employed to evaluate materials based on MBN; however, the application of material evaluation to low-volume targets is challenging because of their low signal-to-noise ratio, which is due to their low volume. Therefore, understanding the influence of the signal-to-noise ratio is important, particularly for low-volume objects. However, very few reports have quantitatively assessed the influence of noise in MBN analysis. In this study, we focused on noise to improve the accuracy of MBN analysis using machine learning, investigated its impact on the prediction accuracy of machine learning models, and explored methods to mitigate its effects. A method for grain size evaluation based on MBN analysis was adopted and performed for Fe-Co alloy wires with different grain sizes. After the measurement of MBN, the relationship between the extracted features from the analysis of MBN by fast Fourier transform and grain size was learned using a gradient boosting decision tree to create a grain size evaluation model, and the coefficient of determination was used to evaluate the prediction accuracy of the grain size evaluation. The machine learning model demonstrated high prediction accuracy (<i>R</i>² = 0.926) across the entire grain size range. Using the model to assess the effect of signal-to-noise ratio, experiments were also conducted using MBN time-series data with artificially applied Gaussian noise. Additionally, from the insight of the distribution of predicted grain sizes, we confirmed that a noise reduction method by averaging the MBN prediction results can improve the prediction accuracy by reducing the effect of noise as expected. This research will lead to the adoption of MBN applications, which are simple and practical methods of material evaluation, for the micro–nano discipline.</p>

DOI： 10.20965/ijat.2024.p0528

Open Access

Web of Science

Scopus

CiNii Research

Prototype of Parallel Plate Type Fast Atom Beam Source and its Improvement of Irradiation Characteristics Open Access

Kato Taisei, Morisaki Ryo, Yamazaki Takahiro, Oka Chiemi, Sakurai Junpei, Hata Seiichi

International Journal of Automation Technology   Vol. 18 ( 4 ) page： 513 - 520   2024.7

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

<p>Fast atom beam (FAB) source is used for surface activated bonding. This process is attracting attention as an essential process for next-generation semiconductor manufacturing. Traditional wafer direct bonding processes require annealing or cannot be directly bonded at room temperature. Therefore, there are restrictions on the materials that can be bonded and the combinations of materials that can be bonded. However, surface activated bonding has made it possible to directly bond dissimilar materials at room temperature. This technology is expected to be applied to the manufacturing of various MEMS and three-dimensional stacking of semiconductors. This bonding process involves bombarding the wafer surface with fast argon atom beam in a vacuum chamber. Irradiation removes oxide layer and contaminants, exposing dangling bonds. By pressing the wafers together, the dangling bonds are bonded together, and a strong bond is achieved. The device that generates this fast argon atom beam is FAB source. This device has been of the type that generates a saddle field electric field. However, this FAB source had a narrow beam irradiation area and was unable to support the recent increase in wafer diameter. Therefore, it was necessary to perform irradiation using multiple FAB sources. At production sites, there is a need to develop new FAB sources that can irradiate large areas. In this study, we developed FAB source in which the beam is generated by parallel plate electrodes. We performed a comparison with the saddle field type FAB source and found that the performance was inferior in initial experiments. Next, we improved the design to operate at higher voltages and increased the aperture area. Through these improvements, we have achieved performance superior to the saddle field type FAB source.</p>

DOI： 10.20965/ijat.2024.p0513

Open Access

Web of Science

Scopus

CiNii Research

Insights into thermally-induced disruption of magnetic-nanoparticle agglomerates Open Access

Junpei, B; Sakurai, J; Hata, S; Oka, C

ALEXANDRIA ENGINEERING JOURNAL   Vol. 96   page： 72 - 81   2024.6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Alexandria Engineering Journal  

We investigated the temperature dependence of agglomeration systems consisting of interacting single-domain magnetic nanoparticles (MNPs). In our study, we utilized electron spin resonance (ESR) experiments to measure how temperature-induced change in agglomerate state affects the peak-to-peak width of ESR spectra (H<inf>pp</inf>) and validated these observations through simulations. Micromagnetic simulations were conducted by combining the classical magnetic dipolar Metropolis Monte Carlo method with the semi-classical macro-spin Landau-Lifshitz-Gilbert finite element method, and the results were compared with experimental findings. Our research elucidates the behavior of thermally-induced disruption of MNP agglomerates. We discovered that the temperature at which MNPs are completely dispersed might correspond to one at which the temperature dependence of H<inf>pp</inf> disappears.

DOI： 10.1016/j.aej.2024.03.101

Open Access

Web of Science

Scopus

Soft magnetostrictive materials: Enhanced magnetostriction of Fe-based nanocrystalline alloys via Ga doping

Sano, K; Yamazaki, T; Morisaki, R; Oka, C; Sakurai, J; Hata, S

SCRIPTA MATERIALIA   Vol. 242   2024.3

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

Soft magnetostrictive materials, having a combination of high soft magnetic properties and substantial magnetostriction, are highly sought for a wide range of applications. Nonetheless, a trade‐off relationship exists between soft magnetic properties and magnetostriction in single‐phase crystalline alloys due to their inherent magnetocrystalline anisotropy. In this study, we introduce the soft magnetostrictive material based on conventional Fe‐based nanocrystalline soft magnetic alloys whose structure quenches magnetocrystalline anisotropy, infused with Ga. All the samples exhibited nanocrystallization behavior and solid‐solution α‐Fe(Ga) was precipitated as a nanocrystalline phase. The net magnetostriction increased with increasing Ga content, concurrently maintaining high magnetic sensitivity with or without Ga addition. As a consequence of this compatibility of properties, the Ga‐doped sample exhibited a magnetostriction susceptibility 1.77 times higher than that of the base alloy. The soft magnetostrictive materials proposed in this study are poised for potential deployment in vibration energy harvesters and strain sensors.

DOI： 10.1016/j.scriptamat.2023.115956

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Scopus

One-dimensional assemblies of magnetic iron-oxide nanoparticles Open Access

Shiojima, T; Sakurai, J; Hata, S; Oka, C

JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 63 ( 3 )   2024.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japanese Journal of Applied Physics  

Although high-aspect-ratio iron-oxide nanoparticles (IONPs) are known to have higher heating efficiency than spherical and cubic IONPs and focused in cancer treatment areas, their synthesis methods require high temperatures, vacuum, reduction conditions, and substantial time. In this study, we proposed and established a facile manufacturing method for one-dimensional assemblies of IONPs, expected to increase heating efficiency similar to high-aspect-ratio IONPs. We investigated how the fabrication conditions affect the length of the assemblies and found that the average length of the one-dimensional assemblies increased with the extension of magnetic-field-application time. This result demonstrates that the length could be controlled by adjusting the duration of the magnetic field application.

DOI： 10.35848/1347-4065/ad26bd

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Scopus

The effects of periodic textured substrate to control diffusion angle on the conversion efficiency of dye-sensitized solar cells Open Access

Kimura, R; Oka, C; Hata, S; Sakurai, J

JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 63 ( 3 )   2024.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japanese Journal of Applied Physics  

We suggested improving the conversion efficiency of dye-sensitized solar cells (DSSCs) by the micro-nano periodic textures to control the diffusion angle of the incident light for certain absorbed wavelengths of the used dye. A periodic texture (Prd-Tx) was designed to enhance the light path of the wavelength of DSSCs’ dye absorption with a wide process window by optical simulation (pitch: 1400 nm, pillar diameter: 460-560 nm, pillar height: more than 500 nm). The Prd-Tx was fabricated by photolithography processes and nanoimprinting (pitch: 1400 nm, pillar diameter: 500 nm, pillar height: 1000 nm). The Prd-Tx increased the DSSCs’ conversion efficiency (η of 3.13%), surpassing our previous best result (refabricated W-Tx, η of 3.08%). It was considered that the ohmic loss was suppressed owing to the Prd-Tx enhanced electrical conductivity at the interface between the transparent electrode, F-doped tin oxide (FTO), and TiO<inf>2</inf>

DOI： 10.35848/1347-4065/ad2417

Open Access

Web of Science

Scopus

色素増感太陽電池の変換効率への周期型回折テクスチャ基板の効果 Open Access

木村 龍太郎, 岡 智絵美, 秦 誠一, 櫻井 淳平

精密工学会学術講演会講演論文集   Vol. 2024S ( 0 ) page： 713 - 714   2024.2

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 精密工学会  

<p>本研究では，微細テクスチャの回折効果を利用してDSSCsの変換効率を向上させることを目指した．光学シミュレーションからDSSCs使用色素に適した回折テクスチャ形状を設計し，ナノインプリント等の微細加工を用いて作製した．回折テクスチャを適用したDSSCsは変換効率を向上させたが，これは回折テクスチャ上に成膜された透明電極FTOの広い表面積により，FTO/TiO₂界面の導電性が向上したことに起因すると考えられた．</p>

DOI： 10.11522/pscjspe.2024s.0_713

Open Access

CiNii Research

Automation of particle emission measurement in surface activated bonding

KATO Taisei, MIYOSHI Yuki, OSHIMA Kyosuke, OKA Chiemi, SAKURAI Junpei, HATA Seiichi

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2024 ( 0 ) page： J114p-05   2024

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

<p>Surface activated bonding is a technology used in semiconductor manufacturing. This technology enables wafers to be bonded directly at room temperature by irradiating them with a fast atom beam. The fast atom beam removes oxides and contaminants from the wafer, thereby activating the surface. A device that emits a fast atom beam is called a fast atom beam source, which generates the beam using plasma from a carbon electrode. However, after several hundred uses, carbon particles are emitted from the electrode surface. These carbon particles cause voids at the wafer bonding interface. In a previous study, a method for in-process quantitative evaluation of carbon particle emissions was proposed. However, hundreds of experiments and measurements were performed manually in the previous study, resulting in widely varying data accuracy. Therefore, in this study, we developed the methods used in previous study and automated all experiments and measurements. The operation of the fast atom beam source and the measurement of particles were automated using “LabVIEW” software. Particle measurement includes photography with a camera and image processing. By automating these processes, the frequency and reliability of measurement improved compared to previous methods. As a result, it was confirmed that particles begin to be emitted after approximately 400 uses, and then continue to be emitted at a constant rate. This behavior is consistent with what has been empirically recorded in mass production sites, confirming the effectiveness of this study.</p>

DOI： 10.1299/jsmemecj.2024.j114p-05

CiNii Research

Post-Process Measurement Device for Internal Stress in Thin Films: Part 1

TAKASE Shun, ASHIKARI Yuki, OKA Chiemi, SAKURAI Junpei, HATA Seiichi

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2024 ( 0 ) page： J221-05   2024

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

<p>Internal stress control is an important technical issue for MEMS composed of thin film structures. In our previous study, we proposed a device to measure the internal stress of thin film structures directly and precisely in post-processing. The device directly measures the strain of a thin film sample due to internal stress as displacement and calculates the internal stress by connecting a thin film sample with springs in series with fixed beams at both ends. However, the measurement resolution of the strain displacement is insufficient. Therefore, we proposed a high precision measurement method using a vernier scale. In this method, line and space patterns are fabricated as a scale by Si etching. The resolution can be adjusted according to the pitch of the line and space, and in this study, patterns with L/S= 2 μm were fabricated to achieve resolutions of 5 MPa.</p>

DOI： 10.1299/jsmemecj.2024.j221-05

CiNii Research

Estimation Of Oxide Film Removal For Surface Activated Bonding By Fast Atom Beam

Takamatsu Yuya, OSHIMA Kyosuke, KATO Taisei, OKA Chiemi, SAKURAI Junpei, HATA Seiichi

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2024 ( 0 ) page： J114p-04   2024

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

<p>Surface activated bonding (SAB) is a technique that involves irradiating surfaces with an inert gas as a fast atom beam (FAB) in a vacuum to remove oxide films and adsorption layers, thereby activating the surfaces and enabling bonding at low pressure. This technique allows for the bonding of dissimilar materials and piezoelectric crystals. Recent research has developed an evaluation method for the irradiation performance of FAB sources using plasma simulation to enhance the irradiation performance for large-diameter Si wafers. However, this method is only applicable when the FAB source is directly facing the wafer, necessitating an investigation into the effects of oblique placement in actual bonding scenarios. In this study, simulations and experiments were conducted to investigate the effects of oblique placement.</p>

DOI： 10.1299/jsmemecj.2024.j114p-04

CiNii Research

Yield improvement of self-roll-up process for micro coils

KANEMATSU Daiki, SANO Kohya, OKA Chiemi, SAKURAI Junpei, HATA Seiichi

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2024 ( 0 ) page： J221p-14   2024

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

<p>We have attempted to improve yield by applying the self-roll-up process, which enables forming of three-dimensional structures with fewer processes than conventional processes, to the micro coil fabrication process. Conventional solenoid micro coils are fabricated mainly by layering and patterning thin films, which makes the process more complex due to the increased number of layers. In the self-roll-up process, rolled structures like a coil shape are fabricated by using the difference in internal stress of the deposited thin films. If even one of them is damaged, the entire coil formed by a series of multiple roll structures will cease to function, so reliable roll-up is necessary. However, since breakage occurred frequently in actual fabrication, the strength of the structure was improved by increasing the overall film thickness and creating a smoother shape in the areas where breakage was frequent. In addition, the burden on the sample was reduced by changing the process that placed a load on the structure. As a result, there was no damage to all the fabricated roll-up structures, and the yield improvement was achieved.</p>

DOI： 10.1299/jsmemecj.2024.j221p-14

CiNii Research

Microstructure and Magnetostrictive Properties of Fe-Ga-based Nanocrystalline Magnetostrictive Materials with High Ga Composition

SANO Kohya, YAMAZAKI Takahiro, OKA Chiemi, SAKURAI Junpei, HATA Seiichi

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2024 ( 0 ) page： J221-02   2024

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

<p>Magnetic materials that exhibit a high reverse magnetostriction effect—soft magnetic properties combined with large magnetostriction—are essential for magnetostrictive vibration energy harvesters. We have proposed Fe-Ga-based nanocrystalline soft magnetostrictive materials that integrate both properties. Previously, we fabricated and evaluated samples with Ga doping of 12 at.% or less, demonstrating that Ga addition enhances magnetostrictive properties. In this study, thin film samples with Ga doping levels up to 30 at.% were fabricated using a radio-frequency magnetron sputtering system. The thin film samples were evaluated for their magnetostrictive curves using the optical leverage method and their microstructure using X-ray diffraction. Results showed that magnetostriction increased with Ga doping below 12 at.% but decreased at 23 at.% or more. This change is attributed to the microstructure. Specifically, the overall magnetostriction may be limited by the precipitation of a compound phase with low magnetostrictive properties or by the magnetostriction of the matrix phase.</p>

DOI： 10.1299/jsmemecj.2024.j221-02

CiNii Research

Quantitative evaluation of particle emission in bidirectional magnetic field-applied fast atom beam source

MIYOSHI Yuki, KATO Taisei, OKA Chiemi, SAKURAI Junpei, HATA Seiichi

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2024 ( 0 ) page： J114p-06   2024

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

<p>Surface-activated bonding, also known as room-temperature bonding, uses fast atom beam sources to create high-performance substrates. This technique is used to bond substrates with different coefficients of thermal expansion, such as those in surface acoustic wave filters substrates for next-generation (5G and 6G) communications. This bonding technique is also expected to be utilized for three-dimensional wafer stacking of semiconductors in the future. According to previous studies, it has been confirmed that the irradiation performance of a conventional fast atom beam source can be improved by applying a bidirectional magnetic field. However, a quantitative evaluation of particle emission suppression has not yet been achieved. In this study, we evaluated the quantitative lifetime of the bidirectional magnetic field-applied fast atom beam source, which had not been quantitatively evaluated before by measuring particle emissions from a fast atom beam source in-process. The experimental results confirmed that the lifetime of the bidirectional magnetic field-applied fast atom beam source is at least 1.5 times longer than that of the conventional saddle-field type fast atom beam source. This result indicates that applying of bidirectional magnetic fields to fast atom beam sources is an effective means to suppress particle emission.</p>

DOI： 10.1299/jsmemecj.2024.j114p-06

CiNii Research

The Fabrication and Evaluation of a Capacitive Pressure Sensor Using Ru-Based Thin Film Metallic Glass with Structural Relaxation by Heat Treatment Open Access

Otsuka, H; Ninoseki, T; Oka, C; Hata, S; Sakurai, J

SENSORS   Vol. 23 ( 23 )   2023.12

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

Microelectromechanical systems (MEMS)-based capacitive pressure sensors are conventionally fabricated from diaphragms made of Si, which has a high elastic modulus that limits the control of internal stress and constrains size reduction and low-pressure measurements. Ru-based thin-film metallic glass (TFMG) exhibits a low elastic modulus, and the internal stress can be controlled by heat treatment, so it may be a suitable diaphragm material for facilitating size reduction of the sensor without performance degradation. In this study, a Ru-based TFMG was used to realize a flattened diaphragm, and structural relaxation was achieved through annealing at 310 °C for 1 h in a vacuum. The diaphragm easily deformed, even under low differential pressure, when reduced in size. A diaphragm with a diameter of 1.7 mm was then applied to successfully fabricate a capacitive pressure sensor with a sensor size of 2.4 mm². The sensor exhibited a linearity of ±3.70% full scale and a sensitivity of 0.09 fF/Pa in the differential pressure range of 0–500 Pa.

DOI： 10.3390/s23239557

Open Access

Web of Science

Scopus

PubMed

Thick film MEMS process using reverse lift-off Open Access

Takase, S; Yamada, K; Nakagawa, Y; Oka, C; Sakurai, J; Hata, S

MICROELECTRONIC ENGINEERING   Vol. 281   2023.9

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

The lift-off process is a microfabrication technique that has the capability of forming thin film structures. However, several issues, such as structural shape and burr formation, arise when applying this method to the formation of thick film structures. Thick film structures formed through the lift-off process exhibit a mountainous cross-sectional shape and non-uniform film thickness due to variations in the width of the structure. These challenges make it difficult to apply the method to MEMS. While the reverse lift-off process addresses some of the structural shape problems, its initial development using metal molds makes it challenging to directly apply to MEMS without modification. Therefore, this paper proposes an adaptation to the Si process and presents a method to reduce burrs. The microfabrication characteristics are evaluated by comparing the cross-sectional shapes of thick metallic glass structures formed through both the lift-off and reverse lift-off processes. The structures formed through the reverse lift-off process exhibit a rectangular cross-sectional shape, and the film thickness remains consistent regardless of the structure's width. However, burrs persist on the backside edge of the structure, which hinders its application to MEMS. This paper confirms that pre-etching the underlying Si substrate into an inverse tapered shape effectively reduces burrs. As an illustration of the improved reverse lift-off process applied to MEMS, MEMS mirror structures are fabricated, and their resonance frequency closely aligns with the design value.

DOI： 10.1016/j.mee.2023.112081

Open Access

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Scopus

Stress measurement based on magnetic Barkhausen noise for thin films

Omae, K; Yamazaki, T; Oka, C; Sakurai, J; Hata, S

MICROELECTRONIC ENGINEERING   Vol. 279   2023.7

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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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国際会議報告：33rd 2022 International Symposium on Micro-NanoMechatronics and Human Science (MHS2022)

岡 智絵美

電気学会論文誌Ｅ（センサ・マイクロマシン部門誌）   Vol. 143 ( 6 ) page： NL6_1 - NL6_1   2023.6

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人 電気学会  

DOI： 10.1541/ieejsmas.143.nl6_1

CiNii Research

Parallel plate type fast atom beam source for large area irradiation

Kato Taisei, Morisaki Ryo, Yamazaki Takahiro, Oka Chiemi, Sakurai Junpei, Hata Seiichi

Proceedings of JSPE Semestrial Meeting   Vol. 2023S ( 0 ) page： 720 - 721   2023.3

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society for Precision Engineering  

DOI： 10.11522/pscjspe.2023s.0_720

CiNii Research

Unidirectional Pore Formation in Resins Using a Magnetic-Nanoparticle-Chain Template Open Access

Kobayashi, A; Sano, K; Sakurai, J; Nagano, H; Hata, S; Oka, C

IEEE MAGNETICS LETTERS   Vol. 14   2023

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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.Fe<inf>3</inf>O<inf>4</inf> 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 (θ) was 30°, the long and short diameters of the pores were approximately 9 and 8 µm, respectively, before MNP removal, and 12 and 8 µm, 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 θ because of the increased UV-masking effect of the MNP chains.

DOI： 10.1109/LMAG.2023.3268851

Open Access

Web of Science

Scopus

Novel measurement method of internal stress in thin films using micro spring structure Open Access

TAKASE Shun, YAMAZAKI Takahiro, OKA Chiemi, SAKURAI Junpei, HATA Seiichi

Mechanical Engineering Journal   Vol. 10 ( 4 ) page： 23-00074 - 23-00074   2023

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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

Open Access

Web of Science

CiNii Research

Effect of Structure on Driving Characteristics of the Tactile Pin Actuator for Reaction Force Variable Tactile Displays

Murase Masanori, Nambara Keita, Oka Chiemi, Hata Seiichi, Sakurai Junpei

IEEJ Transactions on Sensors and Micromachines   Vol. 143 ( 8 ) page： 236 - 241   2023

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

<p>This paper addresses the effect of structure on driving characteristics of the tactile pin actuator using Ti-Ni-Cu high formable shape memory alloy (HFSMA) for reaction force variable tactile displays. The actuator has a cross shaped 3D structure as a tactile pin that is convex at the center. When the tactile pin is pushed by a finger, it transforms and generates a reaction force against the finger. According to the superelastic effect of SMA, the reaction force can be changed by monitoring the device temperature, allowing tactile displays to present softness and hardness. We examined the driving characteristics of the actuators with different tactile pin height by simulation and measurement of actual samples. When the tactile pin height was low, the tactile pin was only deformed elasticity and reaction force was not changed with increasing device temperature. On the other hands, when the tactile pin height was large, the tactile pin was deformed with the induced martensitic transformation, and reaction force increased with increasing device temperature. In addition, the reaction force at certain temperature was increased as the tactile pin height increased, which means that this actuator can vary the range of reaction force by changing its tactile pin height.</p>

DOI： 10.1541/ieejsmas.143.236

Scopus

CiNii Research

In-process measurement of carbon aggregate emissions in surface activated bonding

FUKUI Taisho, KATO Taisei, Oshima Kyosuke, OKA Tiemi, SAKURAI Junpei, HATA Seichi

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2023 ( 0 ) page： J133p-04   2023

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

<p>Surface activated bonding is a three-dimensional wafer stacking technology utilized in the semiconductor field. In this process wafer surfaces are activated by argon atoms irradiated from a fast atom beam source, allowing bonding to take place is at room temperature and low pressure. However, fast atom beam sources present an issue wherein carbon agglomerates, responsible for bonding defects, are discharged alongside the argon atoms. Therefore, it becomes necessary to replace the carbon electrode before these aggregates released. However, quantitatively measuring the ideal time for replacement has been challenging. To address this concern we developed and validated a quantitative in-process measurement method for monitoring discharged carbon agglomerates. This method involves illuminatinge the wafer surface, capturing dark-field images of carbon agglomerates, and performing image processing to quantify measure the amount of discharged carbon agglomerates discharged. In order to establish a reliable relationship between the size of carbon aggregates (maximum Feret diameter) and the corresponding maximum Feret diameter in the dark-field image, we conduct an investigation. The results of the measurement indicated a significant increase in the number of discharged carbon agglomerates after 150 irradiations. Moreover, the largest number of carbon agglomerates was detected in the area between 5 and 7 pixels. These results suggest that the formation of carbon agglomerates occurs through exfolitation, particularly when the irradiation is temporarily interrrupted before the 150th irradiation.</p>

DOI： 10.1299/jsmemecj.2023.j133p-04

CiNii Research

Simulation Estimation Of Oxide Film Removal By Fast Atom Beam

Takamatsu Yuya, Oshima Kyosuke, KATO Taisei, OKA Chiemi, SAKURAI Junpei, HATA Seiichi

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2023 ( 0 ) page： J133p-06   2023

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

<p>Fast atomic beam sources used for surface-activated bonding need to uniformly irradiate a large area. In conventional methods, the irradiation characteristics of such a fast atom beam source must be improved through trial-and-error modifications of the beam aperture arrangement, among other techniques, and by conducting silicon oxide film removal experiments and verification, all of which are inefficient. In this study, we employed the PIC-MCC and DSMC plasma simulation methods to acquire the Ar flux and incident energy distributions on the wafer surface. These distributions predict the amount of oxide film removal caused by the fast atomic beam, and based on them, we constructed a model that predicts the distribution of the amount of film removed. Subsequently, we validated of the prediction model by conducting silicon oxide film removal experiments and obtaining the distributions of the amount of film removed.</p>

DOI： 10.1299/jsmemecj.2023.j133p-06

CiNii Research

Prototype of a unidirectional magnetic field-applied fast atom beam source for surface-activated bonding

OSHIMA Kyosuke, Nomura Wataru, KATO Taisei, OKA Chiemi, SAKURAI Junpei, HATA Seiichi

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2023 ( 0 ) page： J133p-02   2023

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

<p>Surface-activated bonding is a wafer bonding technology where the wafer surface is activated by irradiation with a fast atom beam in a vacuum. We have demonstrated that it can improve the irradiation efficiency and reduce bonding defects caused by carbon emissions by controlling the motion of charged particles with a bidirectional magnetic field applied to the beam source. In recent years, there has been a growing need for a beam source that can irradiate a larger area. In this study, we propose a prototype of a unidirectional magnetic field-applied fast atom beam source that can be lengthened or enlarged. The proposed fast atom beam source achieved more than 1.5 times higher oxide film removal performance compared to the conventionally used fast atom beam source. In a long-term irradiation experiment, the proposed fast atom beam source emitted no carbon particles even after more than twice as many irradiations as the conventional fast atom beam source.</p>

DOI： 10.1299/jsmemecj.2023.j133p-02

CiNii Research

Effect of structural relaxation at bellow crystallization temperature on internal stress of Ni-Nb-Zr thin film amorphous alloys diaphragm for micro electromechanical systems sensors Open Access

Haga, F; Yamazaki, T; Oka, C; Hata, S; Hoshino, Y; Sakurai, J

JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 61 ( SD )   2022.6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japanese Journal of Applied Physics  

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.

DOI： 10.35848/1347-4065/ac5d12

Open Access

Web of Science

Scopus

Combinatorial search for Ti-Ni-Hf high formable shape memory alloys

Inoue, S; Yamazaki, T; Oka, C; Hata, S; Sakurai, J

JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 61 ( 6 )   2022.6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japanese Journal of Applied Physics  

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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Scopus

Examination of Mechanical Properties and Photoelastic Properties of Gel Material for Blood Vesssel Mimics

Yamada, D; Hori, S; Abe, S; Kumeno, Y; Yamazaki, T; Oka, C; Sakurai, J; Hata, S

JOURNAL OF MEDICAL DEVICES-TRANSACTIONS OF THE ASME   Vol. 15 ( 3 )   2021.9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of Medical Devices Transactions of the 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 1.38–2.76 10⁹/Pa by changing the composition ratio, and DN gel changed in the range 0.012–0.029 10⁹/Pa by changing the composition ratio.

DOI： 10.1115/1.4051516

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Fabrication and Evaluation of Actuators for Reaction Force Variable Passive-type Tactile Displays

Nambara Keita, Yamazaki Takahiro, Oka Chiemi, Hata Seiichi, Sakurai Junpei

IEEJ Transactions on Sensors and Micromachines   Vol. 141 ( 9 ) page： 304 - 309   2021.9

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

Scopus

CiNii Research

Combinatorial synthesis of nanocrystalline FeSiBPCuC-Ni-(Nb,Mo) soft magnetic alloys with high corrosion resistance

Yamazaki, T; Tomita, T; Uji, K; Kuwata, H; Sano, K; Oka, C; Sakurai, J; Hata, S

JOURNAL OF NON-CRYSTALLINE SOLIDS   Vol. 563   2021.7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of Non Crystalline Solids  

Fe-based nanocrystalline FeSiBPCuC alloys (NANOMET®) 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)<inf>100−</inf><inf>x</inf><inf>−</inf><inf>y</inf>Ni<inf>x</inf>(Nb,Mo)<inf>y</inf> (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)<inf>95.5</inf>Ni<inf>4.0</inf>Nb<inf>0.5</inf> and (FeSiBPCuC)<inf>97.0</inf>Ni<inf>2.0</inf>Mo<inf>1.0</inf> thin films was deteriorated compared with that of a FeSiBPCuC ribbon.

DOI： 10.1016/j.jnoncrysol.2021.120808

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Thermo-fluid dynamic analysis in a micro-textured evaporator based on microscale infrared/visible observations for loop heat pipes Open Access

Odagiri, K; Oka, C; Kondou, C; Nagano, H

INTERNATIONAL JOURNAL OF MULTIPHASE FLOW   Vol. 140   2021.7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：International Journal of Multiphase Flow  

This paper presents a thermo-fluid dynamic analysis in a micro-textured evaporator for loop heat pipes (LHPs) that has a super wetting surface with ethanol on the basis of an experiment and modeling. In the experiment, three kinds of stainless steel plates with various morphologies of heat transfer surfaces were tested: a normal flat plate, a sandblasted plate, and a micro-groove plate. The measured contact angles between the surfaces and ethanol were 8.2° ± 1.3°, 0°, and 0°, respectively. Evaluation of the heat transfer performance and liquid-vapor interface behavior was conducted using microscale infrared and visible observations. As a result, it was revealed that the sandblasted plate and the micro-groove plate showed 7 times and 20 times higher heat transfer coefficient under high heat flux conditions respectively, compared with the normal flat plate. Different liquid-vapor interface behaviors were found between the plate types. In the modeling, the heat transfer coefficient was predicted for each case. It was found that nucleate boiling heat transfer induced by rough surface increased the heat transfer performance in the case of the sandblasted plate. In addition, it was revealed that the thin film evaporation at the long triple-phase contact line significantly enhanced heat transfer performance in the case of the micro-groove plate. The findings indicate a new promising approach to enhance the heat transfer coefficient of LHP evaporators.

DOI： 10.1016/j.ijmultiphaseflow.2021.103623

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Particle-in-cell Monte Carlo collision simulation and experimental measurement of Ar plasma in a fast atom beam source for surface-activated bonding

Ryo Morisaki, Takahiro Yamazaki, Chiemi Oka, Junpei Sakurai, Takami Hirai, Tomonori Takahashi, Hiroyuki Tsuji, Noriyasu Ohno, and Seiichi Hata

Japanese Journal of Applied Physics   Vol. 60 ( SC ) page： SCCB01   2021.6

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

DOI： 10.35848/1347-4065/abe683

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Nanoscale silica coating of porous stainless steel and its impact on water wettability

Oka, C; Odagiri, K; Nagano, H

JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH   Vol. 18 ( 2 ) page： 601 - 609   2021.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of Coatings Technology and Research  

The water wettability of porous stainless steel specimens was enhanced via a nanoscaled silica coating for application to passive two-phase heat transfer devices. A combination of porous stainless steel and water has attracted attention in the area of the heat transfer devices. However, the water wettability of stainless steel is poor, limiting the performance of the devices. In the present study, the silica coating of the specimens was conducted via a reaction of tetraethyl orthosilicate (TEOS) after pretreatment using NaOH aq. or HCl aq. Energy-dispersive X-ray spectrometry revealed that the amount of silica deposited on the surface was dependent on the pretreatment conditions and the composition of the silica-coating solutions. Measurement of porous properties indicated that the silica coating did not affect pore diameter and gas permeability since the coating was in nanoscale. Microscale contact angles were directly evaluated using an environmental SEM. The specimens showed excellent water wettability when they were covered with numerous tiny silica bumps. When the specimen was pretreated with 2 M NaOH aq. and coated in weak alkaline TEOS solution, the contact angle of the porous stainless steel decreased from 87° to 54° after silica coating. The excellent water wettability originated from the relatively smooth surface and a sufficient coverage ratio, which resulted from the moderate strength of chemical etching of the NaOH aq. and the mild silica-coating condition in the weak alkaline solution.

DOI： 10.1007/s11998-020-00417-1

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Scopus

FABRICATION AND EVALUATION OF A NOVEL ACTUATOR FOR REACTION FORCE VARIABLE PASSIVE-TYPE TACTILE DISPLAYS

Murase, M; Nambara, K; Yamazaki, T; Oka, C; Hata, S; Sakurai, J

2021 21ST INTERNATIONAL CONFERENCE ON SOLID-STATE SENSORS, ACTUATORS AND MICROSYSTEMS (TRANSDUCERS)     page： 663 - 666   2021

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：21st International Conference on Solid State Sensors Actuators and Microsystems Transducers 2021  

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 m, varied the reaction force between 40 and 80 mN at a depth of 100 m, and controlled the electrical resistance linearly with temperature.

DOI： 10.1109/TRANSDUCERS50396.2021.9495608

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Scopus

Measurement of internal stress in thin films using MEMS structures

TAKASE Shun, YAMAZAKI Takahiro, OKA Chiemi, SAKURAI Junpei, HATA Seiichi

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2021 ( 0 ) page： J221-07   2021

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

New Long Life Fast Atom Beam Source for Surface Activated Bonding

Morisaki, R; Sakurai, J; Oka, C; Yamazaki, T; Akao, T; Takahashi, T; Tsuji, H; Ohno, N; Hata, S

2021 7TH INTERNATIONAL WORKSHOP ON LOW TEMPERATURE BONDING FOR 3D INTEGRATION (LTB-3D)     page： 8 - 8   2021

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

DOI： 10.1109/LTB-3D53950.2021.9598414

Web of Science

Development of a fast atom beam gun for surface-activated bonding

Morisaki R.

Precision Engineering   Vol. 62   page： 106 - 112   2020.3

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

DOI： 10.1016/j.precisioneng.2019.11.006

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Fabrication of Novel Microvalves Driven by Heat From Magnetic Nanoparticles

Daiki Miwa, Junpei Sakurai, Seiichi Hata, Chiemi Oka

PROCEEDINGS PAPER，JSME 2020 Conference on Leading Edge Manufacturing/Materials and Processing     page： LEMP2020-8529, V001T08A005   2020

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

DOI： 10.1115/LEMP2020-8529

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Basic study of Ti-Ni-Cu high formable shape memory alloy for soft actuator

ASAI Taihei, AOYAMA Ryosuke, OKA Chiemi, SAKURAI Junpei, HATA Seiichi

The Proceedings of the Materials and processing conference   Vol. 2020.28 ( 0 ) page： 267   2020

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

DOI： 10.1299/jsmemp.2020.28.267

CiNii Research

Fabrication of MEMS Mirror Device Using Reverse Lift-off Process

TAKASE Shun, YAMADA Kyohei, NAKAGAWA Yuki, YAMAZAKI Takahiro, OKA Chiemi, SAKURAI Junpei, HATA Seiichi

The Proceedings of the Materials and processing conference   Vol. 2020.28 ( 0 ) page： 158   2020

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

DOI： 10.1299/jsmemp.2020.28.158

CiNii Research

Fabrication of Novel Microvalves Utilizing Heat from Magnetic Nanoparticles

MIWA Daiki, SAKURAI Junpei, HATA Seiichi, OKA Chiemi

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2020 ( 0 ) page： J22204   2020

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

Development of 3D stress measurement system for surgical simulator

YAMADA Daichi, HORI Simon, YAMAZAKI Takahiro, OKA Chiemi, SAKURAI Junpei, HATA Seiichi

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2020 ( 0 ) page： J24111   2020

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

CiNii Research

Preparation of blood vessel model with two-layer structure for a surgical simulator

YAMADA Daichi, HORI Simon, YAMAZAKI Takahiro, OKA Chiemi, SAKURAI Junpei, HATA Seiichi

The Proceedings of the Materials and processing conference   Vol. 2020.28 ( 0 ) page： 156   2020

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

High performance of proposed FAB source for surface-activated bonding by plasma analysis

MORISAKI Ryo, SAKURAI Jumpei, OKA Chiemi, YAMAZAKI Takahiro, HIRAI Takami, TAKAHASHI Tomonori, TSUJI Hiroyuki, OHNO Noriyasu, HATA Seiichi

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2020 ( 0 ) page： J13105   2020

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

Effect of texture substrates on conversion efficiency in dye-sensitized solar cells

NISHIYASU Yuji, YANG Na, Oka Chiemi, Hata Seiichi, SAKURAI Junpei

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2020 ( 0 ) page： J22207   2020

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<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

Fabrication and drive evaluation of tactile pins for reaction force variable passive type tactile displays using Ti-Ni-Cu high formable shape memory alloys

NAMBARA Keita, IKI Keiichirou, OKA Chiemi, HATA Seiichi, SAKURAI Junpei

The Proceedings of the Materials and processing conference   Vol. 2020.28 ( 0 ) page： 266   2020

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DOI： 10.1299/jsmemp.2020.28.266

CiNii Research

Fabriation of tactile pins for reaction force variable passive type tactile displays using high formable shape memory alloys

NAMBARA Keita, IKI Keiichirou, OKA Chiemi, HATA Seiichi, SAKURAI Junpei

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2020 ( 0 ) page： J22210   2020

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

FABRICATION OF NOVEL MICROVALVES DRIVEN BY HEAT FROM MAGNETIC NANOPARTICLES

Miwa, D; Sakurai, J; Hata, S; Oka, C

PROCEEDINGS OF THE JSME 2020 CONFERENCE ON LEADING EDGE MANUFACTURING/MATERIALS AND PROCESSING, LEMP2020     2020

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

DOI： 10.1115/LEMP2020-8529

Web of Science

Enhanced conversion efficiency in dye-sensitized solar cells using optical textured glass substrates

Nishiyasu Y., Yang N., Oka C., Hata S., Sakurai J.

Mhs 2019 30th 2019 International Symposium on Micro Nanomechatronics and Human Science     2019.12

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

Scopus

Photoelastic stress measurement in real-time for surgery simulator using gel materials

Yamada D., Hori S., Oka C., Sakurai J., Hata S.

Mhs 2019 30th 2019 International Symposium on Micro Nanomechatronics and Human Science     2019.12

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

Scopus

Microvalves Utilizing Heat Generation of Magnetic Nanoparticles

Miwa D., Sakurai J., Hata S., Oka C.

Mhs 2019 30th 2019 International Symposium on Micro Nanomechatronics and Human Science     2019.12

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

Scopus

薄膜金属ガラスの大気中結晶化評価の基礎検討

鬼頭 直希, 櫻井 淳平, 岡 智絵美, 林 裕美, 山崎 宏明, 秦 誠一

精密工学会学術講演会講演論文集   Vol. 2019A ( 0 ) page： 5 - 6   2019.8

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<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

表面活性化接合用新規高速原子ビームガン

森崎 諒, 岡 智絵美, 櫻井 淳平, 平井 隆巳, 高橋 知典, 辻 裕之, 秦 誠一

精密工学会学術講演会講演論文集   Vol. 2019A ( 0 ) page： 687 - 688   2019.8

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

Fabrication and Evaluation of Tactile Pins for Passive Type Tactile Displays using High Formability Shape Memory Alloys

Nambara K., Iki K., Oka C., Hata S., Sakurai J.

2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems and Eurosensors XXXIII, TRANSDUCERS 2019 and EUROSENSORS XXXIII     page： 1854 - 1857   2019.6

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems and Eurosensors XXXIII, TRANSDUCERS 2019 and EUROSENSORS XXXIII  

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

Scopus

Novel Microvalves Driven by Heat Generation from Magnetic Nanoparticles

MIWA Daiki, SAKURAI Junpei, HATA Seiichi, OKA Chiemi

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2019 ( 0 ) page： J22207P   2019

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

<p>Microvalves are used in microfluidic systems such as micro reactors, and micro-total analysis systems (μ-TAS). Most microvalves need electrical wiring on each one, and the need prevents further integration and miniaturization of the microfluidic systems. Hence, we suggest new 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 proposed microvalves consist of thermo-responsive gels and the magnetic nanoparticles with a diameter of 20 nm or less. The nano-scale magnetic particles with superparamagnetic behavior generate heat in an alternating magnetic field. The aim of this study is to verify possibility of the new microvalves. First, Fe₃O₄ magnetic nanoparticles were synthesized and characterized with an X-ray diffractometer, a transmission electron microscope, and a magnetic property measurement system. Then, the heat generation of the synthesized magnetic nanoparticles was measured in an alternating magnetic field. From the measurement, the possibility of the proposed microvalves was verified calculating how long it require to shrink the thermo-responsive gels by heat generated from the magnetic nanoparticles.</p>

DOI： 10.1299/jsmemecj.2019.j22207p

CiNii Research

Fabrication of MEMS mirror using reverse lift-off process

YAMADA Kyohei, NAKAGAWA Yuki, OKA Chiemi, SAKURAI Junpei, YOSHIDA Saori, KIYOMOTO Tomofumi, HATA Seiichi

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2019 ( 0 ) page： J22208P   2019

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<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

Fabrication of textured substrates for dye-sensitized solar cells using polydimethylsiloxane nanoimprint lithography Open Access

Yang Na, Oka Chiemi, Hata Seiichi, Sakurai Junpei

ADVANCED OPTICAL TECHNOLOGIES   Vol. 8 ( 6 ) page： 491 - 497   2019

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

DOI： 10.1515/aot-2019-0010

Web of Science

Scopus

FABRICATION AND EVALUATION OF TACTILE PINS FOR PASSIVE TYPE TACTILE DISPLAYS USING HIGH FORMABILITY SHAPE MEMORY ALLOYS

Nambara Keita, Iki Keiichirou, Oka Chiemi, Hata Seiichi, Sakurai Junpei

2019 20TH INTERNATIONAL CONFERENCE ON SOLID-STATE SENSORS, ACTUATORS AND MICROSYSTEMS & EUROSENSORS XXXIII (TRANSDUCERS & EUROSENSORS XXXIII)     page： 1854 - 1857   2019

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DOI： 10.1109/transducers.2019.8808618

Web of Science

Combinatorial Evaluation for corrosion resistance of High Formable Shape Memory Alloys

CHIZUWA Kaname, OKA Chiemi, HATA Seiichi, SAKURAI Junpei

The Proceedings of the Materials and processing conference   Vol. 2019.27 ( 0 ) page： 207   2019

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<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

Development of real-time photoelastic 3D stress measurement system for surgical simulator

YAMADA Daichi, HORI Simon, OKA Chiemi, SAKURAI Junpei, HATA Seiichi

The Proceedings of the Materials and processing conference   Vol. 2019.27 ( 0 ) page： P01   2019

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<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

Improvement of conversion efficiency of dye-sensitized solar cell by textured substrates

NISHIYASU Yuji, YANG Na, OKA Chiemi, HATA Seiichi, SAKURAI Junpei

The Proceedings of the Materials and processing conference   Vol. 2019.27 ( 0 ) page： P04   2019

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

Development and evaluation of the novel FAB gun

Morisaki R., Hirai Y., Sakurai J., Mizoshiri M., Oka C., Hirai T., Takahashi T., Tsuji H., Hata S.

European Society for Precision Engineering and Nanotechnology Conference Proceedings 19th International Conference and Exhibition Euspen 2019     page： 104 - 105   2019

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：European Society for Precision Engineering and Nanotechnology Conference Proceedings 19th International Conference and Exhibition Euspen 2019  

Argon fast atom beam (FAB) gun is used as a neutral atom beam irradiation source for surface activated bonding (SAB). Since SAB does not require any heat treatments, stress due to difference in thermal expansion coefficients does not occur, and the bonding between not only the same material but also different materials is realizable. However, the conventional FAB gun can be used for only short time because carbon abrasion powders are generated from the worn part of the inside walls of the gun due to argon ion sputtering. We developed the novel FAB gun applied magnetic fields and new position of the anodes in the gun to control the motion of the argon ions and reduce the sputtering. The design concept is that the magnetic fields guide both argon ions and electrons to the irradiation port of the gun and the argon atoms for the irradiation increased. In this study, we investigated the influence of the positions of the magnetic fields and the anodes on the plasma generation, the argon irradiation and the sputtering. With the novel FAB gun, the stable plasma is generated in the vicinity of the irradiation port, and the maximum irradiation amount is 3 times in comparison with the conventional design. Less sputtering of the inside walls of the gun was observed after the irradiation for more than thousands of minutes, while the sputtering with the conventional gun is more observed at the same condition.

Scopus

Basic research on micro processing characteristics of reverse lift-off process

Nakagawa Y., Yamada K., Mizoshiri M., Oka C., Sakurai J., Hata S.

Mhs 2018 2018 29th International Symposium on Micro Nanomechatronics and Human Science     2018.12

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In micro electromechanical systems(MEMS) technology, lift-off processes are general patterning methods for the formation of amorphous alloy thick film structures. However, thicknesses of structures fabricated in this method are not uniform and cross-sectional shapes are not flat because sputtered particles are blocked by the sidewalls of the lift-off layer. In order to solve this problem, a reverse lift-off process is proposed as a new patterning method ^[1]. In the reverse lift-off process, the desired structure is formed on the top of the convex pattern such as the substrate. In contrast to the lift-off process, the thickness of the structure is uniform and the cross-sectional shape is rectangular because sputtered particles are not blocked by the sidewalls. In this research, thick film structures were fabricated in reverse lift-off processes from the width of the convex pattern on the order of micrometers. And the film thickness and the cross-sectional shape of the fabricated structure are measured, and the micro processing characteristics of the reverse lift-off process, which had not yet been elucidated, were investigated. This demonstrates the usefulness of fabricating the thick film micro structures in the reverse lift-off process.

DOI： 10.1109/MHS.2018.8886962

Scopus

Fabrication of miniaturized capacitive pressure sensor using thin film metallic glass

Uejima S., Oka C., Hata S., Sakurai J.

Mhs 2018 2018 29th International Symposium on Micro Nanomechatronics and Human Science     2018.12

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In this paper, we proposed the process of the diaphragm for miniaturizing MEMS capacitive pressure sensor and controlling its sensitivity. We fabricated micro diaphragm using a Ru<inf>65</inf>Zr<inf>30</inf>Al<inf>5</inf>(at.%) thin film metallic glass (TFMG). The as-sputtered TFMG on Si substrate were annealed at 315-440°C for 5 minutes in vacuum. After annealing, micro diaphragms were fabricated by an etching Si substrate using a reactive ion etching system. Although the diaphragm without annealing had dome structure, the diaphragm annealed above 340°C formed a flat structure. The deflection of the diaphragm against applied pressure depended on the annealing temperature and decreased at higher temperatures. The pressure sensor was modeled using this diaphragms. The pressure measurement range and sensitivity were 250 Pa and 6.4×10^-3 pF/Pa, respectively, for annealed at 340°C, and 1800 Pa, and 8.1 × 10^-4 pF/Pa, respectively for annealed at 440°C.

DOI： 10.1109/MHS.2018.8887020

Scopus

Study of a high heat transport Loop Heat Pipe for the automobile thermal management

AONO Yoshitada, NAGANO Hosei, YAMASHITA Seiji, ISHIKIRIYAMA Mamoru, HOSHINO Yu

The Proceedings of Conference of Tokai Branch   Vol. 2018.67 ( 0 ) page： 519   2018

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

DOI： 10.1299/jsmetokai.2018.67.519

CiNii Research

Fabrication of micro diaphragm using thin film metallic glass

ISHIKI Ryuji, Uejima Syohei, Oka Chiemi, SAKURAI Junpei, LIN Yu-Ching, Hata Seiichi

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2018 ( 0 ) page： J2220303   2018

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

Fabrication of Miniaturized Capacitive Pressure Sensor Using Thin Film Metallic Glass

UEJIMA Shohei, OKA Chiemi, HATA Seiichi, SAKURAI Junpei

The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2018 ( 0 ) page： J2220304   2018

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

Evaluation of the bonding methods of Ti-Ni based high formable shape memory alloys

AOYAMA Ryosuke, OKA Chiemi, HATA Seiichi, SAKURAI Junpei

The Proceedings of the Materials and processing conference   Vol. 2018.26 ( 0 ) page： 901   2018

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

DOI： 10.1299/jsmemp.2018.26.901

CiNii Research

Basic research on micro processing characteristics of reverse lift-off process

Nakagawa, Y; Yamada, K; Mizoshiri, M; Oka, C; Sakurai, J; Hata, S

2018 INTERNATIONAL SYMPOSIUM ON MICRO-NANOMECHATRONICS AND HUMAN SCIENCE (MHS)     2018

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

DOI： 10.1109/MHS.2018.8886962

Web of Science

Fabrication of Miniaturized Capacitive Pressure Sensor using Thin Film Metallic Glass

Uejima, S; Oka, C; Hata, S; Sakurai, J

2018 INTERNATIONAL SYMPOSIUM ON MICRO-NANOMECHATRONICS AND HUMAN SCIENCE (MHS)     2018

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

DOI： 10.1109/MHS.2018.8887020

Web of Science

Effect of wettability of a porous stainless steel on thermally induced liquid-vapor interface behavior

Oka C., Odagiri K., Nagano H.

SURFACE TOPOGRAPHY-METROLOGY AND PROPERTIES   Vol. 5 ( 4 )   2017.12

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DOI： 10.1088/2051-672X/aa9499

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Scopus

The role of Bgl2p in the transition to filamentous cells during biofilm formation by Candida albicans.

Chen X, Zhang R, Takada A, Iwatani S, Oka C, Kitamoto T, Kajiwara S

Mycoses   Vol. 60 ( 2 ) page： 96-103   2017.2

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DOI： 10.1111/myc.12554

PubMed

Heat generation of core-shell particles composed of biodegradable polymer and iron oxide Reviewed

C. Oka, K. Ushimaru, N. Horiishi, T. Tsuge, Y. Kitamoto

Journal of the Magnetics Society of Japan   Vol. 40   page： 126-131   2016

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Biodegradable and magnetic core-shell composite particle prepared by emulsion solvent diffusion method Reviewed

Chiemi Oka, Kazunori Ushimaru, Nanao Horiishi, Takeharu Tsuge, Yoshitaka Kitamoto

Japanese Journal of Applied Physics   Vol. 55   page： 02BE01   2016

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DOI： 10.7567/JJAP.55.02BE01

Core-shell composite particles composed of biodegradable polymer particles and magnetic iron oxide nanoparticles for targeted drug delivery Reviewed

Chiemi Oka, Kazunori Ushimaru, Nanao Horiishi, Takeharu Tsuge, Yoshitaka Kitamoto

Journal of Magnetism and Magnetic Materials   Vol. 381   page： 278-284   2015.1

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DOI： 10.1016/j.jmmm.2015.01.005