Faculty Profiles - OKA Chiemi

Papers - OKA Chiemi

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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

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

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

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

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(N-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.

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

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

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.

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

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

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.

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

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

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

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

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

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 Publishing type：Research paper (scientific journal) 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

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

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

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

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

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

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

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．

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

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

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．

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

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

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

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.

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

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

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.

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

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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Papers - OKA Chiemi