Faculty Profiles - HATA Seiichi

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

Shin Inoue, Takahiro Yamazaki, Chiemi Oka, Seiichi Hata, Junpei Sakurai

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

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

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

DOI： 10.35848/1347-4065/ac6a97

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 Reviewed

Fuyuki Haga, Takahiro Yamazaki, Chiemi Oka, Seiichi Hata, Yuto Hoshino, Junpei Sakurai

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

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

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

DOI： 10.35848/1347-4065/ac5d12

Stress-Driven Magnetic Barkhausen Noise Generation in FeCo Magnetostrictive Alloy Reviewed

Yamazaki, T; Furuya, Y; Hata, S; Nakao, W

IEEE TRANSACTIONS ON MAGNETICS Vol. 58 ( 1 ) 2022.1

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

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

DOI： 10.1109/TMAG.2021.3126898

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

Daichi Yamada, Simon Hori, Shuhe Abe, Yuki Kumeno, Takahiro Yamazaki, Chiemi Oka, Junpei Sakurai, Seiichi Hata

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

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

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

DOI： 10.1115/1.4051516

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

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

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.

DOI： 10.1541/ieejsmas.141.304

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

Takahiro Yamazaki, Tatsuya Tomita, Katsutoshi Uji, Hidenori Kuwata, Kohya Sano, Chiemi Oka, Junpei Sakurai, Seiichi Hata

JOURNAL OF NON-CRYSTALLINE SOLIDS Vol. 563 page： 120808 2021.7

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

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

DOI： 10.1016/j.jnoncrysol.2021.120808

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

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 60 ( SC ) 2021.6

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

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

DOI： 10.35848/1347-4065/abe683

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

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

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

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

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

DOI： 10.1109/TRANSDUCERS50396.2021.9495608

New Long Life Fast Atom Beam Source for Surface Activated Bonding Reviewed

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

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

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

DOI： 10.1109/LTB-3D53950.2021.9598414

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

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

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.

DOI： 10.1299/jsmemecj.2021.j221-07

Material search in the age of AI applying microfabrication

HATA Seiichi

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2021 ( 0 ) page： K041-01 2021

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

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

DOI： 10.1299/jsmemecj.2021.k041-01

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

Ryo Morisaki, Yuuki Hirai, Chiemi Oka, Mizue Mizoshiri, Takahiro Yamazaki, Junpei Sakurai, Takami Hirai, Tomonori Takahashi, Hiroyuki Tsuji, Seiichi Hata

Precision Engineering Vol. 62 page： 106 - 112 2020.3

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

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

DOI： 10.1016/j.precisioneng.2019.11.006

Fabrication of novel microvalves driven by heat from magnetic nanoparticles

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

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

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

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

DOI： 10.1115/LEMP2020-8529

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

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

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

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 (η of 2.74%), 18% for N-Tx (η of 3.01%) and 26% for D-Tx (η of 3.22%) compared to DSSC with flat glass (η of 2.55%).

DOI： 10.1299/jsmemecj.2020.j22207

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

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

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

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.

DOI： 10.1299/jsmemecj.2020.j22210

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

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

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.

DOI： 10.1299/jsmemecj.2020.j13105