2021/10/25 更新

写真a

ミツマタ テツ
三俣 哲
MITSUMATA Tetsu
所属
教育研究院 自然科学系 生産デザイン工学系列 准教授
工学部 工学科 准教授
職名
准教授
外部リンク

学位

  • 博士(理学) ( 1999年3月   北海道大学 )

研究キーワード

  • エラストマー

  • 磁性粒子

  • 天然物化学

  • 多糖

  • バイオプラスチック

  • 高分子ゲル

  • 磁性エラストマー

  • ソフトマテリアル

  • 刺激応答性材料

  • 電磁気物性

  • レオロジー

  • ソフトコンポジット

  • 材料物性

  • 天然高分子

  • 高分子アクチュエータ

研究分野

  • ナノテク・材料 / 高分子材料

  • ナノテク・材料 / 構造材料、機能材料

  • ナノテク・材料 / 複合材料、界面

  • ナノテク・材料 / 高分子化学

経歴(researchmap)

  • 新潟大学   研究推進機構   研究教授

    2016年10月 - 現在

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  • 新潟大学   自然科学系(工学部)   准教授

    2014年4月 - 現在

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  • 山形大学大学院   理工学研究科   助教

    1999年10月 - 2014年3月

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  • 山形大学   ベンチャービジネスラボラトリ-   講師

    1999年4月 - 1999年9月

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経歴

  • 新潟大学   工学部 工学科   准教授

    2017年4月 - 現在

  • 新潟大学   材料開発工学   准教授

    2014年4月 - 2017年3月

学歴

  • 北海道大学大学院   理学研究科   博士後期課程

    1995年10月 - 1999年3月

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  • 北陸先端科学技術大学院大学   材料科学研究科   博士前期課程

    1993年10月 - 1995年9月

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  • 愛媛大学   教養部   物理学教室

    1993年4月 - 1993年9月

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  • 愛媛大学   理学部   物理学科

    1989年4月 - 1993年3月

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留学歴

  • フランス国立科学研究センター ポールパスカル研究所   文部科学省在外研究員

    2002年5月 - 2002年11月

 

論文

  • Interfacial self-assembly of polysaccharide rods and platelets bridging over capillary lengths

    Gargi Joshi, Kosuke Okeyoshi, Fitri Adila Amat Yusof, Tetsu Mitsumata, Maiko K. Okajima, Tatsuo Kaneko

    Journal of Colloid and Interface Science   591   483 - 489   2021年6月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    DOI: 10.1016/j.jcis.2021.02.017

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  • Critical Electric Field and Activation Energy for Electric Conductivity for Biopolyimide Using 4,4 '-Diamino-alpha-truxillic Acid and 1,2,3,4-Cyclobutanetetracarboxylic Dianhydride 査読

    Fitri Adila Amat Yusof, Takumi Noda, Kenji Takada, Tatsuo Kaneko, Mika Kawai, Tetsu Mitsumata

    CHEMISTRY LETTERS   49 ( 8 )   929 - 931   2020年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    Biopolyimides poly(ATA-CBDA) made from of 4,4'-diamino-alpha-truxillic acid dimethyl ester (ATA) and 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) were synthesized and its electric volume resistivity measured at various electric voltages at 10-60 degrees C. The volume resistivity for Kapton and biopolyimide films showed a sudden decrease at a critical electric field of 2.6 x 10(7) and 1.0 x 10(7) V/m, respectively. The activation energy at low electric field for Kapton and biopolyimide was 68 and 90 kJ/mol, respectively, meanwhile at high electric field for Kapton and biopolyimide was 45 and 74 kJ/mol, respectively. These results indicate that the carriers for electric conduction for biopolyimide weakly interact with the polymer chain and the biopolyimide contains many conductive carriers than Kapton.

    DOI: 10.1246/cl.200232

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  • Optimal Plasticizer Content for Magnetic Elastomers Used for Cell Culture Substrate 査読

    Mayuko Watanabe, Yukiko Tanaka, Daiki Murakami, Masaru Tanaka, Mika Kawai, Tetsu Mitsumata

    CHEMISTRY LETTERS   49 ( 3 )   280 - 283   2020年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    The effect of a magnetic field on the water contact angle for magnetic elastomers with various plasticizer contents was investigated. At a plasticizer content below 60 wt %, there was no change in contact angle when a magnetic field of 370 mT was applied. For magnetic elastomers with a plasticizer content above 65 wt %, a change in contact angle of approximately 8.0 degrees was observed (e.g. 38 degrees at 0 mT and 46 degrees at 370 mT for 65 wt % plasticizer content). Dynamic viscoelastic measurements showed that magnetic elastomers with a plasticizer content below 60 wt % demonstrate the magnetorheological (MR) effect with changes in storage modulus higher than similar to 1 MPa. Atomic force microscopy for magnetic elastomer with a plasticizer content of 50 wt % revealed that the averaged Young's modulus was 233 +/- 52.1 kPa at 370 mT and 83 +/- 5.4 kPa at 0 mT, indicating that the MR effect is caused not only on a bulk but also on a mesoscopic scale. Magnetic elastomers specialized for cell culture were obtained by optimizing the plasticizer content, that exhibit the MR effect with changes in storage modulus from 1.3 x 10(4) Pa to 9.4 x 10(5) without changing the surface properties.

    DOI: 10.1246/cl.190929

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  • Electric Volume Resistivity for Biopolyimide Using 4,4′-Diamino-α-truxillic acid and 1,2,3,4-Cyclobutanetetracarboxylic dianhydride 査読

    Shunsuke Kato, Fitri Adila Amat Yusof, Toyohiro Harimoto, Kenji Takada, Tatsuo Kaneko, Mika Kawai, Tetsu Mitsumata

    Polymers   11 ( 10 )   1552 - 1552   2019年9月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:MDPI AG  

    Biopolyimides poly(ATA-CBDA), made from of 4,4′-diamino-α-truxillic acid dimethyl ester (ATA) and 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), is synthesized and measured its electric volume resistivity at various experimental conditions. The effects of film size, thickness, drying time, and the electric field strength on electric resistivity are investigated and compared with polyimide (Kapton). The electric resistivity for all polyimide and biopolyimide are distributed in the range of 1015–1016 Ωcm, which shows that biopolyimide has high electrical insulation as well as polyimide. The electric resistivity strongly depends on film thickness, which suggests that electric resistivity is a function of electric field strength. The critical electric field for polyimide and biopolyimide films are determined to be 5.8 × 107 V/m and 3.2 × 107 V/m, respectively. Humidity was found to strongly affect the electric resistivity; ~1016 Ωcm at 34% RH and ~1013 Ωcm at 60% RH for both polyimide and biopolyimide films.

    DOI: 10.3390/polym11101552

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  • Dataset of various characterizations for novel bio-based plastic poly(benzoxazole-co-benzimidazole) with ultra-low dielectric constant 査読

    Aniruddha Nag, Mohammad Asif Ali, Makoto Watanabe, Maninder Singh, Kittima Amornwachirabodee, Shunsuke Kato, Tetsu Mitsumata, Kenji Takada, Tatsuo Kaneko

    Data in Brief   25   104114 - 104114   2019年8月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    DOI: 10.1016/j.dib.2019.104114

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  • Micro-deposition control of polysaccharides on evaporative air-LC interface to design quickly swelling hydrogels 査読

    Joshi Gargi, Okeyoshi Kosuke, Mitsumata Tetsu, Kaneko Tatsuo

    JOURNAL OF COLLOID AND INTERFACE SCIENCE   546   184 - 191   2019年6月

  • High-performance poly( benzoxazole/benzimidazole) bio-based plastics with ultra-low dielectric constant from 3-amino-4-hydroxybenzoic acid 査読

    Nag Aniruddha, Ali Mohammad Asif, Watanabe Makoto, Singh Maninder, Amornwachirabodee Kittima, Kato Shunsuke, Mitsumata Tetsu, Takada Kenji, Kaneko Tatsuo

    POLYMER DEGRADATION AND STABILITY   162   29 - 35   2019年4月

  • Railway Actuator Made of Magnetic Elastomers and Driven by a Magnetic Field 査読

    Yasuhiro Umehara, Yusuke Yamanaga, Shota Akama, Shunsuke Kato, Shogo Kamoshita, Mika Kawai, Tetsu Mitsumata

    10 ( 1351 )   1 - 7   2018年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  • Elastic Properties of Magnetorheological Elastomers in a Heterogeneous Uniaxial Magnetic Field 査読 国際誌

    Kikuchi Takehito, Kobayashi Yusuke, Kawai Mika, Mitsumata Tetsu

    INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES   19 ( 10 )   2018年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.3390/ijms19103045

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  • Particle Dispersibility and sound propagation of ultrasounds for magnetic soft composites 査読

    Yuri Tsujiei, Shota Akama, Junko Ikeda, Yoshihiro Takeda, Mika Kawai, Tetsu Mitsumata

    Reactive and Functional Polymers   130   1 - 7   2018年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier B.V.  

    We measured the sound velocity for magnetic soft composites consisting of a polymeric matrix of polyurethane and a magnetic particle of carbonyl iron or barium ferrite, and investigated the effect of the particle dispersibility on the sound velocity at 10 MHz for the composites. Morphological observations and dynamic viscoelastic measurements at 1 Hz were also carried out, and the results revealed that the carbonyl iron was dispersive particle and the barium ferrite was aggregative particle in the polyurethane matrix. The sound velocity for polyurethane elastomer without magnetic particles was 1444 ± 12 m/s and it decreased with the volume fraction of magnetic particles. The sound velocity of magnetic composites with barium ferrite obeyed the Reuss model at whole volume fractions, however, magnetic composites with carbonyl iron exhibited an under deviation from the Reuss model at volume fractions above ~0.053. It was also found that the longitudinal modulus was insensitive to the creation of the particle network and sensitive to the aggregation of magnetic particles. The threshold seen in the longitudinal modulus was different from that in the nonlinear parameter of viscoelasticity, indicating that the ultrasound of 10 MHz detects microscopic heterogeneity of particle dispersion.

    DOI: 10.1016/j.reactfunctpolym.2018.05.011

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  • A Feature in Magnetorheological Effect for Polysaccharide Magnetic Hydrogels 査読

    Akama Shota, Ikeda Junko, Kawai Mika, Mitsumata Tetsu

    CHEMISTRY LETTERS   47 ( 9 )   1240 - 1242   2018年9月

  • Chain Formation for Uncross-Linked and Cross-Linked Polyurethane Magnetic Elastomers 招待 査読

    Shuhei Sasaki, Mayuko Watanabe, Mika Kawai, Tetsu Mitsumata

    Research and Reviews in Materials Science and Chemistry   8 ( 1 )   1 - 20   2018年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  • Effect of Sonication Time on Magnetorheological Effect for Monomodal Magnetic Elastomers 査読

    Mayuko Watanabe, Junko Ikeda, Yoshihiro Takeda, Mika Kawai, Tetsu Mitsumata

    Gels   4 ( 49 )   1 - 8   2018年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  • Time-Dependent Electric Conductivity and Dielectric Breakdown for Magnetic Soft Composites at High-Electric Fields 査読

    Aeronautics and Aerospace Open Access Journal   2 ( 2 )   80 - 83   2018年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  • Negative Thixotropic Behavior for Sacran Aqueous Solutions 査読

    Mitsumata Tetsu

    YAKUGAKU ZASSHI-JOURNAL OF THE PHARMACEUTICAL SOCIETY OF JAPAN   138 ( 4 )   497 - 501   2018年4月

  • Magnetically Tunable Vibration Transmissibility for Polyurethane Magnetic Elastomers 査読 国際誌

    Endo Hiroyuki, Kato Shunsuke, Watanebe Mayuko, Kikuchi Takehito, Kawai Mika, Mitsumata Tetsu

    POLYMERS   10 ( 1 )   2018年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.3390/polym10010104

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  • Frequency spectra of vibration transmissibility for magnetic elastomers with various plasticizer contents 査読

    Yasuhiro Umehara, Hiroyuki Endo, Mayuko Watanabe, Takehito Kikuchi, Mika Kawai, Tetsu Mitsumata

    AIMS Materials Science   5 ( 1 )   44 - 53   2018年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AIMS Press  

    The effect of plasticizer content on the vibration absorbing properties for polyurethane elastomers was investigated. A natural frequency appeared on the frequency spectra at around 100 Hz. The natural frequency linearly decreased, and the transmissibility also decreased with the plasticizer content. Magnetic elastomers containing carbonyl iron particles with a dimeter of 7.0 μm also showed a natural frequency at ~260 Hz, and the natural frequency significantly decreased with the plasticizer content. The decrease in the transmissibility with the plasticizer content was larger than that for polyurethane elastomers. The natural frequency for magnetic elastomers increased by several ten Hz by a magnetic field of 60 mT although the transmissibility was independently of the plasticizer content. The effect of load on the natural frequency for these elastomers was also investigated, and it was found that the natural frequency is proportional to the storage modulus, G, with different two slopes depending on the mass of the system, m. The linear relation between the natural frequency and (G'/m)1/2 revealed that the observed vibration can be basically described by a simple harmonic oscillation.

    DOI: 10.3934/matersci.2018.1.44

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  • Effects of biopolyimide molecular design on their silica hybrids thermo-mechanical, optical and electrical properties 査読

    S. Dwivedi, S. Sakamoto, S. Kato, T. Mitsumata, T. Kaneko

    RSC Advances   8 ( 25 )   14009 - 14016   2018年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Royal Society of Chemistry  

    Polymers, derived from bio-derived resources, have gained considerable momentum because of a lower dependence over conventional fossil-based resources without compromising the materials' thermo-mechanical properties. Unique characteristics of organic and inorganic materials can be incorporated by a combination of both to obtain hybrid materials. We have recently developed a series of transparent biopolyimides (BPI) from a biologically derived exotic amino acid, 4-aminocinnamic acid (4ACA) to yield 4-amino truxillic ester (4ATA ester) derivatives. In the present research, the polyimide-precursor was subjected to sol-gel polycondensation reactions with silicon-alkoxide followed by annealing under vacuo to yield a biopolyimide-silica hybrid. The biopolyimide structures (4ATA acid/ester) and their silica hybrids thermo-mechanical, electrical and optical performance were evaluated. It was found that the biopolyimide with 4ATA(ester) yields thermo-mechanically robust films with very high electrical stability as well as optical transparency, plausibly due to the uniform dispersion of the silica particles in the biopolyimide matrix.

    DOI: 10.1039/c8ra01965g

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  • Magnetically-tunable rebound property for variable elastic devices made of magnetic elastomer and polyurethane foam 査読

    Tsubasa Oguro, Hiroyuki Endo, Mika Kawai, Tetsu Mitsumata

    MATERIALS RESEARCH EXPRESS   4 ( 12 )   2017年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    A device consisting of a phase of magnetic elastomer, a phase of polyurethane foam (PUF), and permanent magnet was fabricated and the stress-strain curves for the two-phase magnetic elastomer were measured by a uniaxial compression measurement. A disk of magnetic elastomer was adhered on a disk of PUF by an adhesive agent. The PUF thickness was varied from 1 mm to 5 mm while the thickness of magnetic elastomers was constant at 5 mm. The stress at a strain of 0.15 for the two-phase magnetic elastomers was evaluated in the absence and in the presence of a magnetic field of 410 mT. The stress at 0 mT decreased remarkably with the PUF thickness due to the deformation of the PUF phase. On the other hand, the stress at 410 mT slightly decreased with the thickness; however, it kept high values even at high thickness. When the PUF thickness was 5 mm, the maximum stress increment with 45 times to the off-field stress was observed. An experiment using ping-pong balls demonstrated that the coefficient of restitution for the two-phase magnetic elastomers can be dramatically altered by the magnetic field.

    DOI: 10.1088/2053-1591/aa9d51

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  • Magnetic-field Sensitivity for Monomodal Magnetic Elastomers with Various Volume Fractions of Magnetic Particles 査読

    Jinta Nanpo, Shota Abe, Mika Kawai, Tetsu Mitsumata

    CHEMISTRY LETTERS   46 ( 11 )   1628 - 1630   2017年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    The relationship between magnetic-field sensitivity and the volume fraction of magnetic particles for magnetic elastomers was investigated. The magnetic-field dependence of the storage modulus for magnetic elastomers was measured by dynamic viscoelastic measurements under magnetic fields with a constant sweep rate of 3.7 mT s(-1). The magnetic-field sensitivity was determined by the initial slope of the storage modulus using an exponential function. It was revealed that the maximum magnetic-field sensitivity was 1.8 x 10(-2) mT(-1) at the maximum volume fraction of magnetic particles.

    DOI: 10.1246/cl.170735

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  • Magnetic field gradient and sample size effect on magnetomechanical response for magnetic elastomers 査読

    Tsubasa Oguro, Hiroyuki Endo, Takehito Kikuchi, Mika Kawai, Tetsu Mitsumata

    REACTIVE & FUNCTIONAL POLYMERS   117   25 - 33   2017年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    We studied the size effect of disk-shaped magnetic elastomers, which were placed on a permanent magnet, on their magnetomechanical response for the permanent magnet. The diameter of the magnetic elastomers varied from 14 to 40 mm, whereas the diameter of the permanent magnet was constant at 30 or 35 nun. The smallest magnetic elastomer did not exhibit magnetomechanical response for both 30- and 35-mm-diameter permanent magnets; however, a clear response was observed when the diameter of the magnetic elastomer equaled that of the permanent magnet. Magnetic field distribution revealed a steep gradient of magnetic fields at the fringe of permanent magnets. Image analyses indicated that the bottom of magnetic elastomers was restricted to deform along the horizontal direction under compression. In the vertical direction, the magnetostriction due to the magnetic attractive force from permanent magnets was negligibly small. Therefore, the size-dependent behavior of magnetomechanical response is considered a pinning effect wherein the bottom of magnetic elastomers was restricted by the magnetic field gradient in the horizontal direction. We also analyzed the magnetomechanical response of magnetic elastomers when magnetic fields were applied by square-or ring-shaped permanent magnets.

    DOI: 10.1016/j.reactfunctpolym.2017.05.009

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  • Effects of Field Strength and Sample Size on Magnetomechanical Response for Magnetic Elastomers by Using Permanent Magnets 査読

    Tsubasa Oguro, Jinta Nanpo, Takehito Kikuchi, Mika Kawai, Tetsu Mitsumata

    CHEMISTRY LETTERS   46 ( 4 )   547 - 549   2017年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    We studied the effects of magnetic field strength and sample size on the magnetomechanical response for disk-shaped magnetic elastomers placed on a permanent magnet. The diameter of magnetic elastomer was varied between 14-40 mm, whereas the height was constant at 5 mm. The stress was measured with a unidirectional compression apparatus. It was found that the smallest magnetic elastomer with 14mm diameter did not exhibit magnetomechanical response, on the other hand, clear response was observed for magnetic elastomers with 35mm diameter. This sample size effect was observed at both 310 and 420mT.

    DOI: 10.1246/cl.161182

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  • Transition from Linear to Nonlinear Viscoelasticity for Bimodal Magnetic Elastomers under a Magnetic Field 査読

    Kazushi Nagashima, Jinta Nanpo, Mika Kawai, Tetsu Mitsumata

    CHEMISTRY LETTERS   46 ( 3 )   366 - 367   2017年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    We have investigated the transition from linear viscoelasticity to nonlinear viscoelasticity for bimodal magnetic elastomers under a magnetic field. For bimodal magnetic elastomers, the transition strain increased remarkably with the volume fraction of nonmagnetic particles. For monomodal magnetic elastomers, the transition strain also increased with the volume fraction of magnetic particles; however, the increment was not significant. A possible mechanism of the widening of the linear viscoelastic plateau by nonmagnetic particles is discussed.

    DOI: 10.1246/cl.161079

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  • Sound Velocity and Particle Dispersibility for Magnetic Elastomers Containing Carbonyl Iron and Barium Ferrite Particles 査読

    Yuri Tsujiei, Tsubasa Oguro, Mika Kawai, Tetsu Mitsumata

    CHEMISTRY LETTERS   46 ( 3 )   364 - 365   2017年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    Sound velocity of magnetic elastomers containing carbonyl iron and barium ferrite particles has been investigated by using an ultrasound pulse-echo method at 10 MHz. The sound velocity for magnetic elastomers containing barium ferrite was independent of the sample thickness, and the mean sound velocity was determined to be 1187 +/- 5 ms(-1). The sound velocity for magnetic elastomers containing carbonyl iron linearly decreased with the sample thickness, and the values (954-1031 ms(-1)) were lower than those of barium ferrite. Microphotographs revealed that carbonyl iron particles were randomly dispersed and barium ferrite particles were heterogeneously dispersed in the polyurethane matrix. The relationship between the sound velocity and the particle dispersibility is discussed.

    DOI: 10.1246/cl.161080

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  • Electric Conductivity and Dielectric-Breakdown Behavior for Polyurethane Magnetic Elastomers 査読

    Shuhei Sasaki, Yuri Tsujiei, Mika Kawai, Tetsu Mitsumata

    JOURNAL OF PHYSICAL CHEMISTRY B   121 ( 7 )   1740 - 1747   2017年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    The electric-voltage dependence of the electric conductivity for cross-linked and un-cross-linked magnetic elastomers was measured at various magnetic fields, and the effect of cross-linking on the electric conductivity and the dielectric-breakdown behavior was investigated. The electric conductivity for uncross-linked elastomers at low voltages was independent of magnetic fields and the volume fraction of magnetic particles, indicating the electric conduction in the polyurethane matrix. At high voltages, the electric conductivity increased with the magnetic field, showing the electric conduction via chains of magnetic particles. On the other hand, the electric conductivity at low voltages for cross-linked elastomers with volume fractions below 0.06 was independent of the magnetic field, suggesting the electric conduction in the polyurethane matrix. At volume fractions above 0.14, the electric conductivity increased with the magnetic field, suggesting the electric conduction via chains of magnetic particles. At high voltages, the electric conductivity for cross-linked elastomers with a volume fraction of 0.02 was independent of the magnetic field, indicating the electric conduction through the polyurethane matrix. At volume fractions above 0.06, the electric conductivity suddenly increased at a critical voltage, exhibiting the dielectric breakdown at the bound layer of magnetic particles and/or the discontinuous part between chains.

    DOI: 10.1021/acs.jpcb.6b12875

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  • Sample Size Effect of Magnetomechanical Response for Magnetic Elastomers by Using Permanent Magnets 査読

    Tsubasa Oguro, Shuhei Sasaki, Yuri Tsujiei, Mika Kawai, Tetsu Mitsumata, Tatsuo Kaneko, Miklos Zrinyi

    JOURNAL OF NANOMATERIALS   2017年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:HINDAWI PUBLISHING CORP  

    The size effect of magnetomechanical response of chemically cross-linked disk shaped magnetic elastomers placed on a permanent magnet has been investigated by unidirectional compression tests. A cylindrical permanent magnet with a size of 35 mm in diameter and 15 mm in height was used to create the magnetic field. The magnetic field strength was approximately 420 mT at the center of the upper surface of the magnet. The diameter of the magnetoelastic polymer disks was varied from 14 mm to 35 mm, whereas the height was kept constant (5 mm) in the undeformed state. We have studied the influence of the disk diameter on the stress-strain behavior of the magnetoelastic in the presence and in the lack of magnetic field. It was found that the smallest magnetic elastomer with 14 mm diameter did not exhibit measurable magnetomechanical response due to magnetic field. On the opposite, the magnetic elastomers with diameters larger than 30 mm contracted in the direction parallel to the mechanical stress and largely elongated in the perpendicular direction. An explanation is put forward to interpret this size-dependent behavior by taking into account the nonuniform field distribution of magnetic field produced by the permanent magnet.

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  • Magnetic-Field Sensitivity of Storage Modulus for Bimodal Magnetic Elastomers 査読

    Jinta Nanpo, Kazushi Nagashima, Yasuhiro Umehara, Mika Kawai, Tetsu Mitsumata

    JOURNAL OF PHYSICAL CHEMISTRY B   120 ( 50 )   12993 - 13000   2016年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    The magnetic-field dependence of the storage modulus for bimodal magnetic elastomers consisting of carbonyl iron with a diameter of 2.8 mu m (magnetic) and aluminum hydroxide with a diameter of 1.4 mu m (nonmagnetic) was measured, and the effect of nonmagnetic particles on the magnetic-field sensitivity of the storage modulus was investigated. The coefficient of the magnetic-field sensitivity for the monomodal magnetic elastomer increased from 0.018 to 0.026 mT(-1) for the bimodal one by embedding nonmagnetic particles of 6.6 vol %. At volume fractions above 5.4 vol %, the bimodal magnetic elastomer exhibited significant nonlinear viscoelasticity at 0 mT and a high storage modulus, at 500 mT, simultaneously, the coefficient of the magnetic-field sensitivity demonstrated high values. This strongly indicates that both the particles form a particle network at the off-field, and they make a well-developed chain structure under magnetic fields. The time profiles of the storage modulus for bimodal magnetic elastomers can be fitted by a linear combination of two exponential functions with two characteristic times showing the alignment of magnetic particles. The alignment time for the fast and slow processes was distributed around 3.3 +/- 0.3 and 176 +/- 12 s, respectively. The alignment time was independent of the volume fraction of the nonmagnetic particles; however, the increment in the storage modulus for the fast process significantly increased at volume fractions above 5.4 vol %. It was also revealed that the coefficient of the magnetic-field sensitivity can be scaled by a power function of the inclement in the storage modulus divided by the off-field modulus, Delta G'/G(0)', not only for the bimodal magnetic elastomers but also for the monomodal ones.

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  • Amphoteric Response of Loss Factor for Bimodal Magnetic Elastomers by Magnetic Fields 査読

    Kazushi Nagashima, Mika Kawai, Tetsu Mitsumata

    CHEMISTRY LETTERS   45 ( 8 )   1033 - 1034   2016年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    We have investigated the mechanical loss factor for bimodal magnetic elastomers containing magnetic and nonmagnetic particles. The bimodal magnetic elastomer exhibited amphoteric response of loss factor by magnetic fields depending on the strain amplitude; i.e. negative response at low strains and significant positive response at high strains. The mechanism of amphoteric response seen in bimodal magnetic elastomers is discussed.

    DOI: 10.1246/cl.160327

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  • Fabrication of a poly(dimethylsiloxane) microstructured surface imprinted from patterned silicon wafer with a self-cleaning property 査読

    Shingo Tamesue, Eri Takahashi, Shunsuke Kosugi, Kazuhiro Fukami, Tetsu Mitsumata, Norio Tsubokawa, Tetsuo Sakka, Takeshi Yamauchi

    Polymer Journal   48 ( 7 )   835 - 838   2016年7月

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    掲載種別:研究論文(学術雑誌)  

    A study was conducted to fabricate a microstructure on a poly(dimethylsiloxane) (PDMS) surface using a porous silicon wafer as a mold. The microstructured PDMS surfaces were deposited with gold and imaged using scanning electron microscopy (SEM). The average height and width of the microrods measured using scanning electron microscopy imaging were 10 and 8 μm. The results show that the water contact angle was 103° on the flat surface and 131° on the microstructured surface, resulting in the microstructure increased hydrophobicity.

    DOI: 10.1038/pj.2016.34

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  • Magnetic-field Sensitivity for Magnetic Elastomers with Various Elasticities 査読

    Jinta Nanpo, Mika Kawai, Tetsu Mitsumata

    CHEMISTRY LETTERS   45 ( 7 )   785 - 786   2016年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    The effect of plasticizer content on the magnetic-field sensitivity for magnetic elastomers has been investigated while maintaining the concentration of magnetic particles at 70 wt %. The magnetic-field dependence of the storage modulus for magnetic elastomers was measured by dynamic viscoelastic measurements under magnetic fields with a sweep rate of 3.7 mTs(-1). The magnetic-field sensitivity, determined by the initial slope of the storage modulus using an exponential function, increased from 1.0 x 10(-3) to 1.8 x 10(-2) mT(-1) with increasing plasticizer content.

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  • Highly Tolerant and Durable Adhesion between Hydrogels Utilizing Intercalation of Cationic Substituents into Layered Inorganic Compounds 査読

    Shingo Tamesue, Kento Yasuda, Shingo Noguchi, Tetsu Mitsumata, Takeshi Yamauchi

    ACS MACRO LETTERS   5 ( 6 )   704 - 708   2016年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    Adhering hydrogel systems are important particularly in the medical field because they can be used as adhesives cross linking between living tissues. In this research, hydrogels including cationic substituents prepared via free-radical polymerization were brought into contact after applying an aqueous dispersion of the layered inorganic compound Micromica to their surfaces. As a result, the hydrogels adhered to each other due to the intercalation of cationic substituents included in the gel networks into the interlayers of Micromica. As the water content ratio of hydrogels decreased, the adhesive strength came to be higher, and finally the adhesively bonded joint supported a tensile load of 10 kg. Moreover, it was confirmed that the adhered hydrogels have high tolerance toward various environments, such as high or low temperatures and solvents.

    DOI: 10.1021/acsmacrolett.6b00337

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  • Photo-Triggered Microgel Aggregation Using o-Nitrobenzaldehyde as Aggregating Power Source 査読

    Shingo Tamesue, Shinji Abe, Tetsu Mitsumata, Norio Tsubokawa, Takeshi Yamauchi

    JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY   54 ( 10 )   1317 - 1322   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-BLACKWELL  

    In this work, cationic and anionic microgels which are mainly formed from thermal responsive polymer, poly(N-isopropylacrylamide), are prepared and mixed in water. These microgels interact with each other due to the electrostatic interaction, and aggregate voluntarily. By applying the microgel aggregating system, photo-responsive aggregating system is constructed by using o-nitrobenzaldehyde (NBA), which reacts and releases hydrogen triggered by photo stimuli. The microgel aggregates in an aqueous solution of NBA re-disperse depending on the irradiation time of UV light. In addition, by masking the UV irradiated area, the resultant shapes of microgel aggregates are controlled. The aggregated microgel shows rapid and drastic volume changes in response to heat. (C) 2015 Wiley Periodicals, Inc.

    DOI: 10.1002/pola.27985

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  • Extraordinary Swelling of Hydrogels Physically Crosslinked by Megamolecular Chain Sacran 査読

    Wataru Ito, Miho Yamaki, Mika Kawai, Tetsu Mitsumata, Maiko K. Okajima, Tatsuo Kaneko

    CHEMISTRY LETTERS   45 ( 3 )   339 - 340   2016年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    Physically crosslinked sacran gels were prepared, and the degree of swelling in pure water and in 0.9 wt % NaCl solution was measured. The sacran gel showed anomalous swelling with a degree of swelling of 6100 in pure water and 530 in the saline solution. The degree of swelling varied remarkably by the pH of the pre-gel solution. This high swelling ratio might originate from the large mesh consisting of extremely long chains of sacran.

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  • Photoelectric properties of C-60-poly(ethylene glycol) and poly(3,4-ethylenedioxythiophene) composite gel prepared via a low-temperature organic-solvent process 査読

    Zhang Huiqiu, Masaru Ichinose, Hideaki Takahashi, Shingo Tamesue, Tetsu Mitsumata, Masayuki Yagi, Norio Tsubokawa, Takeshi Yamauchi

    POLYMER JOURNAL   48 ( 2 )   163 - 168   2016年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:NATURE PUBLISHING GROUP  

    C-60 fullerene derivatives, which are formed by grafting polymer chains on a C-60 fullerene, can improve the solubility of C-60 in solvents. These derivatives are able to composite with various functional polymers to form interpenetrating network gel structures. In this study, a composite gel composed of the C-60 fullerene derivatives and poly(3,4-ethylenedioxythiophene)(PEDOT) was prepared using a low-temperature organic-solvent process, and its photoelectric properties were evaluated. Furthermore, the poly(ethylene glycol) (PEG) radicals were successfully trapped in the fullerene (C-60), which worked as a cross-linking point to yield the C-60-PEG gel. Then, PEDOT was composited with the gel using chemical oxidative polymerization to form the C-60-PEG/PEDOT gel. The structure of the film prepared using this composite material was identified. The C-60-PEG/PEDOT film had an amorphous network structure and the UV response was much higher than that of the C-60-PEG gel. In addition, it was estimated that PEDOT was synthesized inside the C-60-PEG gel and formed nanoscale junctions between C-60 and PEDOT, which was beneficial for the movement of electrons and holes. The photocurrent was observed by irradiating the C-60-PEG/PEDOT gel electrode with UV or simulated sunlight. The power conversion efficiency (PCE) was calculated as 1.2 x 10(-3)%. Therefore, it is expected that the C-60-PEG/PEDOT material is applicable for the photoelectric field, such as solar cells.

    DOI: 10.1038/pj.2015.65

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  • Various Actuating Motions of Conducting Polymers Actuators on Inorganic Conductive Substrate Formed from Polypyrrole and Gold 査読

    Shingo Tamesue, Genki Endo, Ryota Ishizaki, Tetsu Mitsumata, Norio Tsubokawa, Takeshi Yamauchi

    CHEMISTRY LETTERS   44 ( 12 )   1700 - 1702   2015年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    In order to create more flexible and robust soft actuators, organic/inorganic hybrid actuating fibers were prepared by coating gold fibers in polypyrrole using electropolymerization. The linear, coiled, and helical hybrid fibers were prepared by deforming gold fibers in advance. The obtained fibers exhibit various actuating motions, such as bending, stretching, and rotating motions, due to shrinking and expanding of polypyrrole by doping and de-doping of lithium cations. Merit of the actuating fibers prepared in this research is that the fibers are thin and can be easily combined. Hence, the actuating forces of the fibers caused by doping and de-doping can be amplified by combining the fibers. As a result, heavier weights could be lifted, proportional to the number of fibers combined.

    DOI: 10.1246/cl.150851

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  • Preparation of poly(N-isopropylacrylamide)-terminated carbon nanotubes and determining their aggregation properties in response to infrared light and heating 査読

    Shingo Tamesue, Suguru Hasegawa, Ryota Ishizaki, Kumi Hashimoto, Tetsu Mitsumata, Norio Tsubokawa, Takeshi Yamauchi

    POLYMER JOURNAL   47 ( 10 )   709 - 712   2015年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:NATURE PUBLISHING GROUP  

    DOI: 10.1038/pj.2015.47

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  • バイオTRIZを活用した酵素複合導電性高分子の作製とバイオセンサへの応用 査読

    山内健, 綱田英里子, 幸田貴司, 為末真吾, 三俣哲, 坪川紀夫, 小林秀敏

    材料試験技術   60 ( 3 )   159 - 163   2015年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  • Preparation of Porous Poly(pyrrole) Utilizing Agar Particles as Soft Template and Evaluation of Its Actuation Property 査読

    Kentaro Obata, Shingo Tamesue, Kumi Hashimoto, Tetsu Mitsumata, Norio Tsubokawa, Takeshi Yamauchi

    MACROMOLECULAR MATERIALS AND ENGINEERING   300 ( 8 )   766 - 771   2015年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

    Porous poly(pyrrole) (PPy) films are prepared by utilizing agar particles (APs) of various average diameters as templates. The size of the APs can be regulated by the concentration of agar during preparation, and these APs can be removed easily from PPy films by heating up to 90 degrees C after formation of the films by electropolymerization because agar shows a thermally reversible sol-gel transition. The pores in the surface of PPy films can be controlled by the size of APs utilized as templates. The porous PPy films have higher mechanical strength and exhibit the more dynamic actuating behavior than the flat PPy films. Moreover, spring-like actuating motion is induced by the presence of pores in the surface of helically shaped PPy films.

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  • Nonmagnetic particles enhance magnetoelastic response of magnetic elastomers 査読

    Kazushi Nagashima, Shunta Kanauchi, Mika Kawai, Tetsu Mitsumata, Shingo Tamesue, Takeshi Yamauchi

    JOURNAL OF APPLIED PHYSICS   118 ( 2 )   2015年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    The elastic modulus for bimodal magnetic elastomers has been investigated by compression measurements under large deformation. The bimodal magnetic elastomers consist of carbonyl iron magnetic particles and zinc oxide nonmagnetic particles. The Young's modulus for monomodal magnetic elastomers was 8.94 x 10(4) Pa at 0 mT and 1.65 x 10(5) Pa at 320 mT, respectively. The relative change in the Young's modulus for monomodal magnetic elastomer was 1.8, and it was raised to 5.8 only by mixing with the nonmagnetic particles of 9.6 vol. %. It is considered that the modulus enhancement originates from the stress transfer by the additional chains of magnetic particles via nonmagnetic particles. The electric resistivity analysis revealed that 27% of magnetic particles in a strand of chains were replaced by nonmagnetic particles. It was shown in the present study that the bimodal magnetic elastomers endured against a compression load of 30 N. (c) 2015 AIP Publishing LLC.

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  • Effect of Plasticizer on the Magnetoelastic Behavior for Magnetic Polyurethane Elastomers 査読

    Yukio Kimura, Shunta Kanauchi, Mika Kawai, Tetsu Mitsumata, Shingo Tamesue, Takeshi Yamauchi

    CHEMISTRY LETTERS   44 ( 2 )   177 - 178   2015年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    Magnetic polyurethane elastomers containing various plasticizers were synthesized, and the effect of plasticizers on the magnetoelastic behavior has been investigated. The storage modulus for magnetic elastomers at 0 mT decreased with plasticizer content, whereas the storage modulus at 500 mT dramatically increased. The increment in the storage modulus by magnetic fields increased with plasticizer content indicating a well-developed chain structure of magnetic particles. It was found that the on-field storage modulus can be scaled by the off-field modulus independently of the kind of plasticizers.

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  • Anisotropic swelling in hydrogels formed by cooperatively aligned megamolecules

    M. K. Okajima, R. Mishima, K. Amornwachirabodee, T. Mitsumata, K. Okeyoshi, T. Kaneko

    RSC Advances   5 ( 105 )   86723 - 86729   2015年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Royal Society of Chemistry  

    Sacran is a supergiant cyanobacterial polysaccharide with an extremely high absolute molecular weight that exceeds 107 g mol-1 (molecular length: over 30 μm). Sacran forms milli-scaled orientation domains in aqueous liquid crystalline (LC) state, even in trace concentrations i.e. 0.3 wt%. Aqueous sacran films that are cast from a LC state and annealed between 70-140 °C form self-standing sheets composed of oriented hydrogels. When sacran films swell, they experience changes in size that are 70 fold higher in relation to thickness than those that occur in relation to width. Either an increase in film thickness or a decrease in sacran chain length reduces swelling anisotropy, demonstrating that stress that occurs during drying can be effectively used to propagate the cooperative alignment of LC chains on a micrometer sized scale comparable with the thickness of self-standing films.

    DOI: 10.1039/c5ra18585h

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  • Enhanced Magnetoelastic Behavior of Magnetic Elastomers with Layered Structure 査読

    Tsubasa Oguro, Shunta Kanauchi, Tetsu Mitsumata, Shingo Tamesue, Takeshi Yamauchi

    CHEMISTRY LETTERS   43 ( 12 )   1885 - 1886   2014年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    We synthesized layered magnetic elastomers with polymer films and investigated the magnetoelastic behavior using dynamic viscoelastic measurements. The storage modulus at 0 mT was nearly independent of the sheets of films, while the storage modulus at 500 mT dramatically increased. The storage modulus at 500 mT for magnetic elastomers with 4 films was 2.1 MPa, which was 1.3 MPa higher than that of magnetic elastomers without layered structure. It can be considered that the stress transfer among imperfect short chains of magnetic particles is enhanced by inserting polymer films.

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  • Magnetic particle composite gels 査読

    Tetsu Mitsumata

    Soft Actuators: Materials, Modeling, Applications, and Future Perspectives   9784431547679   271 - 284   2014年7月

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    記述言語:英語   掲載種別:論文集(書籍)内論文   出版者・発行元:Springer Japan  

    Magnetic soft materials containing solid state magnetic particles demonstrate various motions and magnetorheological behavior in response to magnetic fields. When a rotational magnetic field is applied to magnetic gels containing with magnetized particles, the magnetic gels exhibit rotational motion. When a non-uniform magnetic field is applied to magnetic gels, the elongation of magnetic gels is observed. The rotational motion of magnetic gels can be applied to a fluid pump that delivers water in straight and spiral tubes. A bead of magnetic gels loaded with drugs undergoes accelerated drug release depending on the rotation rates. The elongational motion of magnetic gels can be applied to an elongation-contraction actuator or a microvalve. Under uniform magnetic fields, the magnetic gels show variable viscoelastic behavior depending on the field-strength, which is called the magnetorheological effect. The dynamic modulus of magnetic hydrogels increases by two orders of magnitude synchronized with magnetic fields. The magnetorheological effect of magnetic gels can be applied to haptic devices or intelligent dampers. Actuators and magnetorheological effects of magnetic soft materials consisting of solid state magnetic particles are described.

    DOI: 10.1007/978-4-431-54767-9_20

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  • Very Small Amounts of Carbon Nanotubes to Weaken Thixotropy of Polysaccharide Gels 査読

    Takuro Goda, Takashi Kurita, Tetsu Mitsumata, Masahito Sano

    CHEMISTRY LETTERS   43 ( 7 )   988 - 990   2014年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    Additions of single-walled carbon nanotubes (SWCNTs) to kappa-carrageenan gels weaken thixotropy. The minimum volume fraction of SWCNT to kappa-carrageenan necessary to affect thixotropy is about 10(-4). Confocal Raman microscopy reveals that SWCNTs are preferentially located close to the hole perimeter native to the gel network. This suggests that the destruction of network initiates at the hole perimeter. By locating at the critical region, only a small amount of SWCNTs is sufficient to resist initiating destruction.

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  • Ionic state and chain conformation for aqueous solutions of supergiant cyanobacterial polysaccharide 査読

    Tetsu Mitsumata, Takashi Miura, Natsuki Takahashi, Mika Kawai, Maiko K. Okajima, Tatsuo Kaneko

    Physical Review E - Statistical, Nonlinear, and Soft Matter Physics   87 ( 4 )   2013年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We have investigated the electric conductivity, dielectric relaxation behavior, and viscosity for the aqueous solution of cyanobacterial megamolecules, molecular weight =1.6×107 g/mol, named sacran. Sacran is an anionic polyelectrolyte which has carboxylate and sulfate groups on the saccharide chain. The electric conductivity and the zero shear viscosity demonstrated three crossover concentrations at 0.004, 0.02, and 0.1 wt%. The viscosity was found to be scaled as ∼c1.5, ∼c0.5, ∼c1.5, and ∼c3.0 with increasing the sacran concentration. At 0.1 wt%, the sacran chain formed a weak gel which exhibits macroscopic liquid crystal domains including Schlieren texture. Therefore, these crossover concentrations are considered to be the overlap concentration, entanglement concentration, and gelation concentration (or critical polyelectrolyte concentration), respectively. Dielectric relaxation analysis exhibited the fact that sacran has two types of counterions with different counterion-polyion interaction, i.e., strongly bound and loosely bound counterions. The dielectric parameters such as relaxation time or relaxation strength are sensitive to both the entanglement concentration and the gelation concentration, but not the overlap concentration. The number density of bound counterions calculated from the relaxation strength revealed that the counterion is condensed on the sacran chain with raising the sacran concentrations. The decrease in the charge density of the sacran chain reduces the repulsive force between the chains and this would cause the helix transformation or gelation behavior. The chain conformation of sacran in pure water and the gelation mechanism are discussed in relation with the behavior of polyelectrolytes and liquid crystals. © 2013 American Physical Society.

    DOI: 10.1103/PhysRevE.87.042607

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  • Wide-range Modulation of Dynamic Modulus and Loss Tangent for Magnetic Elastomers Containing Submilimeter Magnetic Particles 査読

    Naoya Chiba, Ken Yamamoto, Tsukasa Hojo, Mika Kawai, Tetsu Mitsumata

    CHEMISTRY LETTERS   42 ( 3 )   253 - 254   2013年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    Magnetic elastomers containing magnetic particles with a diameter of 235 mu m have been synthesized, and the magnetic response of the elasticity was investigated. The storage modulus for the magnetic elastomer with a volume fraction of 0.18 increased from 12.5 kPa to 2.43 MPa by applying a magnetic field of 500 mT. The relative change in the storage modulus was 194 times, which is higher than that of magnetic elastomers containing small iron particles (ca. 58 times at 2.5 mu m). It was also revealed that the magnetic elastomer exhibited wide-range modulation of loss tangent by varying magnetic fields.

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  • Anionic complexes of MWCNT with supergiant cyanobacterial polyanions 査読

    Maiko K. Okajima, Amit Kumar, Akihiko Fujiwara, Tetsu Mitsumata, Daisaku Kaneko, Tetsuya Ogawa, Hiroki Kurata, Seiji Isoda, Tatsuo Kaneko

    BIOPOLYMERS   99 ( 1 )   1 - 9   2013年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-BLACKWELL  

    Multi-walled carbon nanotubes (MWCNTs) were well dispersed in an aqueous solution of the cyanobacterial polysaccharide, sacran, with an ultra-high molecular weight >10 million g/mol. MWCNTs powder was put into aqueous solutions of various polysaccharides including sacran and was dispersed under sonication. As a result of the turbidity measurement of the supernatant, it was found that sacran showed the highest MWCNT-dispersion efficiency of all the polysaccharides used here. Cryogenic transmission electron microscopic (Cryo-TEM) studies directly demonstrated the existence of MWCNTs in the supernatant, and high-resolution TEM observation revealed that MWCNTs covered by sacran chains made their efficient dispersion in water. Raman spectroscopy demonstrated the existence of MWCNT in dried sample from supernatant and the interaction between MWCNT and sacran. The ?-potential measurement of the dispersion indicated the negative surface charges of the sacran/MWCNT complexes. Then the MWCNT complexes were able to fabricate by ionic interaction; electrophoresis of the anionic complex formed the sacran/MWCNT gels on the anode while the droplet of sacran/MWCNT dispersion formed gel beads in the presence of the lanthanoid cations. (c) 2012 Wiley Periodicals, Inc.

    DOI: 10.1002/bip.22129

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  • Magnetoelastic Behavior of Bimodal Magnetic Hydrogels Using Nonmagnetic Particles 査読

    Suguru Ohori, Kouko Fujisawa, Mika Kawai, Tetsu Mitsumata

    CHEMISTRY LETTERS   42 ( 1 )   50 - 51   2013年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    Bimodal magnetic hydrogels consisting of magnetic and nonmagnetic particles were synthesized, and the magnetic response to the dynamic modulus of the gels was investigated. The change in the storage modulus for magnetic gels containing only magnetic particles exhibited 0.9 MPa by applying a magnetic field of 500 mT. The change in the storage modulus kept a high value although the magnetic particles were replaced with nonmagnetic particles by 34%. It can be considered that the magnetic interaction extends to the length of 4 to 6 microns via 2 or 3 nonmagnetic particles.

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  • Prototype of haptic device for sole of foot using magnetic field sensitive elastomer 査読

    T. Kikuchi, Y. Masuda, M. Sugiyama, T. Mitsumata, S. Ohori

    Journal of Physics: Conference Series   412 ( 1 )   2013年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Institute of Physics Publishing  

    Walking is one of the most popular activities and a healthy aerobic exercise for the elderly. However, if they have physical and / or cognitive disabilities, sometimes it is challenging to go somewhere they don't know well. The final goal of this study is to develop a virtual reality walking system that allows users to walk in virtual worlds fabricated with computer graphics. We focus on a haptic device that can perform various plantar pressures on users' soles of feet as an additional sense in the virtual reality walking. In this study, we discuss a use of a magnetic field sensitive elastomer (MSE) as a working material for the haptic interface on the sole. The first prototype with MSE was developed and evaluated in this work. According to the measurement of planter pressures, it was found that this device can perform different pressures on the sole of a light-weight user by applying magnetic field on the MSE. The result also implied necessities of the improvement of the magnetic circuit and the basic structure of the mechanism of the device. © Published under licence by IOP Publishing Ltd.

    DOI: 10.1088/1742-6596/412/1/012036

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  • Magnetism and viscoelasticity of magnetic elastomers with wide range modulation of dynamic modulus 査読

    Tetsu Mitsumata, Suguru Ohori, Atomu Honda, Mika Kawai

    SOFT MATTER   9 ( 3 )   904 - 912   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    Magnetism, dynamic viscoelasticity, mechanical property, and durability of magnetic elastomers consisting of polyurethane and carbonyl iron particles were investigated. Magnetic measurements revealed that the magnetic permeability of the magnetic elastomers can be explained by the linear combination of the magnetic permeability of magnetic particles and polyurethane. Dynamic viscoelastic measurements showed that the magnetic particles are randomly dispersed in the elastomer. On applying a magnetic field of 500 mT, the magnetic elastomers demonstrated a drastic change in the dynamic modulus; the storage modulus increased from 6.5 kPa to 1.6 MPa, and the loss modulus increased from 3.6 kPa to 0.16 MPa. This drastic change in the dynamic modulus was observed at all frequencies from 0.01 Hz to 3 Hz. The critical volume fraction showing the transition from a random dispersion to a chain structure decreased significantly with the magnetic field. Compression tests revealed that the magnetic elastomers exhibited high mechanical toughness with high breaking strain exceeding 0.8. Durability tests showed the magnetoviscoelastic behavior of the magnetic elastomers was maintained for 1.5 years after the synthesis without degradation.

    DOI: 10.1039/c2sm26717a

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  • Enhancement of magnetoelastic behavior of bimodal magnetic elastomers by stress transfer via nonmagnetic particles 査読

    Tetsu Mitsumata, Suguru Ohori, Naoya Chiba, Mika Kawai

    SOFT MATTER   9 ( 42 )   10108 - 10116   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    The magnetoelastic behavior of bimodal magnetic elastomers consisting of magnetic particles, carbonyl iron, and nonmagnetic particles, zinc oxide, has been investigated by dynamic viscoelastic measurements. The storage modulus of bimodal magnetic elastomers increased under a magnetic field of 500 mT. The change in the storage modulus was enhanced by adding nonmagnetic particles at volume fractions above a certain volume fraction of 0.02, indicating the occurrence of stress transfer by a chain structure of magnetic particles via nonmagnetic particles. The critical volume fraction at 500 mT determined by percolation analysis was nearly independent of the diameter of nonmagnetic particles. However, at low magnetic fields below 160 mT, the critical volume fraction was found to decrease with the particle diameter. Substituting magnetic particles with nonmagnetic ones, the change in the storage modulus of bimodal magnetic elastomers monotonically decreased with the substitution ratio of magnetic particles. The mechanism of the enhanced magnetoelastic response for bimodal magnetic elastomers is discussed.

    DOI: 10.1039/c3sm51836a

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  • Photoshrinkage in Polysaccharide Gels with Trivalent Metal Ions 査読

    Maiko K. Okajima, Quyen Thi le Nguyen, Seiji Tateyama, Hideaki Masuyama, Takumi Tanaka, Tetsu Mitsumata, Tatsuo Kaneket

    BIOMACROMOLECULES   13 ( 12 )   4158 - 4163   2012年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    The giant anionic polysaccharide "sacran", which is composed of 6-deoxyhexoses, pentoses, uronic acids as well as hexoses, showed hydrophobization and insolubilization phenomena in response to ultraviolet light irradiation. The sacran solution became turbid, and microparticles were formed by photoirradiation. To visualize the results of this photoreaction, anionic polysaccharide gels cross-linked by metal cations were used. As a result, we observed that sacrangels with trivalent metal ions gradually contracted depending on the photoirradiation energy. In contrast, alginate gels used as a comparison degraded instead of contracting. This photoshrinkage of the sacran gels may be attributed to the hydrophobization of uronic acid based on photodecarboxylation. We propose that sacran-metal ion gels can function as effective, photoresponsive gels.

    DOI: 10.1021/bm301440e

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  • Magnetically Tunable Elasticity for Magnetic Hydrogels Consisting of Carrageenan and Carbonyl Iron Particles 査読

    Tetsu Mitsumata, Atomu Honda, Hiroki Kanazawa, Mika Kawai

    JOURNAL OF PHYSICAL CHEMISTRY B   116 ( 40 )   12341 - 12348   2012年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    A new class of magnetoelastic gel that demonstrates drastic and reversible changes in storage modulus without using strong magnetic fields was obtained. The magnetic gel consists of carrageenan and carbonyl iron particles. The magnetic gel with a volume fraction of magnetic particles of 0.30 exhibited a reversible increase by a factor of 1400 of the storage modulus upon a magnetic field of 500 mT, which is the highest value in the past for magnetorheological soft materials. It is considered that the giant magnetoelastic behavior is caused by both high dispersibility and high mobility of magnetic particles in the carrageenan gel. The off-field storage modulus of the magnetic gel at volume fractions below 0.30 obeyed the Krieger-Dougherty equation, indicating random dispersion of magnetic particles. At 500 mT, the storage modulus was higher than 4.0 MPa, which is equal to that of magnetic fluids, indicating that the magnetic particles move and form a chain structure by magnetic fields. Morphological study revealed the evidence that the magnetic particles embedded in the gel were aligned in the direction of magnetic fields, accompanied by stretching of the gel network. We conclude that the giant magnetoelastic phenomenon originates from the chain structure consisting of magnetic particles similar to magnetic fluids.

    DOI: 10.1021/jp3049372

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  • Trivalent metal-mediated gelation of novel supergiant sulfated polysaccharides extracted from Aphanothece stagnina 査読

    Quyen Thi le Nguyen, Maiko Okajima, Tetsu Mitsumata, Kai Kan, Hang Thi Tran, Tatsuo Kaneko

    COLLOID AND POLYMER SCIENCE   290 ( 2 )   163 - 172   2012年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGER  

    Anionic polysaccharide (PS) was extracted from Aphanothece stagnina biomaterials where trivalent metal ions were remarkably condensed from environmental water. Structural analyses indicated that the PS was considered to be a kind of sulfated rhamnoglucan-containing uronic acid at a composition of 23 mol% and that the total composition of anionic groups such as sulfate and carboxylate was 31 mol% to the monosaccharide residues. Since the PS was found to be a huge macromolecule with an ultra-high molecular weight (3.14x10(7) g/mol), the simple calculation indicated that about 9.5x10(4) anions exist on one chain of the PS. The electric conductivity of the highly anionic PS solutions indicated that the metal ions such as Ga(3+), La(3+), and Ca(2+) complexed ionically with PS chains. The PS formed the gels as a result of trivalent metal complexation, but the gelation behavior of the PS was different from that of the representative metal-complexable polysaccharide, alginate, in terms of the minimum gel formation concentration and the average molecular weight between cross-linking points.

    DOI: 10.1007/s00396-011-2528-3

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  • Design and Evaluation of Unit for Haptic Device on Foot 査読

    Yasunobu Masuda, Takehito Kikuchi, Wataru Kobayashi, Kento Amano, Tetsu Mitsumata, Suguru Ohori

    2012 IEEE/SICE INTERNATIONAL SYMPOSIUM ON SYSTEM INTEGRATION (SII)   541 - 545   2012年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Walking is a popular recreation activity. In addition, it is a mild and healthy exercise for the elderly. However, people suffering from physical and / or cognitive disorders have a difficulty in going out and walking in real environments. Therefore we have proposed a virtual walking system with a haptic device on feet. This system consists of visual, sound, and haptic devices to present various kinds of ambient information for users. The development of the haptic interface for feet soles is a main topic of this paper. We discuss a use of magnetic field sensitive elastomers (MSEs) as working materials for the device. In the previous report, we developed an electromagnet as a testbed of MSE and evaluated it performance. According to the measurement of planter pressures, this device can perform different pressures on soles by applying magnetic field. The result also implied necessities of the improvement of the magnetic circuit and basic structure for more feasible device. In this paper, we propose a new structure to control a frictional resistance force that is generated on the surface of the MSE and a metal pin. In addition, we propose to use this device as a single unit for the haptic device on feet. According to the compressive test of the unit, the maximum force that can be controlled with the unit is insufficient yet. However, it appears that we can control frictional force with the proposed structure. We also conducted a simulation to estimate required values of the performance for the unit. It is much higher than the current state of the unit. We have to improve the performance of the unit in the future.

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  • Measurement of Plantar Pressure and Development of Prototype for Haptic Device on Sole of Foot with Magnetic Field Sensitive Elastomer 査読

    Takehito Kikuchi, Yasunobu Masuda, Masao Sugiyama, Tetsu Mitsumata, Suguru Ohori

    2012 4TH IEEE RAS & EMBS INTERNATIONAL CONFERENCE ON BIOMEDICAL ROBOTICS AND BIOMECHATRONICS (BIOROB)   1188 - 1193   2012年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    A magnetic field sensitive elastomer (MSE) is a compound of magnetic particles and non-magnetic elastomers. This is a functional material whose elasticity can be adjusted with an external magnetic field. The final goal of this study is to develop a virtual walking system using a haptic device on soles of feet with the MSE. First, we measured the difference of planter pressures when subjects (3 young healthy students) stepped on two different types of floor (dot-type braille block and flat floor). The differences of the normalized pressures were about 2 similar to 4, and these values are one of the development goal of the device. Next, we designed an electromagnet and evaluate the difference of plantar pressure with / without magnetic field on the MSE. According to the results, the difference of the normalized pressure depended on the weight of subjects. The difference of the normalized pressure was 2.3 for a light subject. However, there were not clear differences for heavier subjects. We should consider the basic elasticity of the MSE to develop a practical device.

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  • Design of Unit for Haptic Device on Foot 査読

    Yasunobu Masuda, Takehito Kikuchi, Wataru Kobayashi, Tetsu Mitsumata, Suguru Ohori

    2012 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND BIOMIMETICS (ROBIO 2012)   2012年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Walking and traveling are popular recreation for the elderly in Japan. These activities are also mild activities exercises and have good effects for their health. However, people suffering from physical and / or cognitive disorders have a difficulty in going out and walking in real environments. Therefore we have proposed a virtual walking system with a haptic device on feet. This system consists of visual, sound, and haptic devices to present various kinds of ambient information for users. Especially, development of the haptic interface for feet soles is a new challenge. In this paper, we discuss a use of magnetic field sensitive elastomers (MSEs) as working materials for the device. We developed an electromagnet as a testbed of MSE and evaluated it performance. According to the measurement of planter pressures, this device can perform different pressures on soles by applying magnetic field. The result also implied necessities of the improvement of the magnetic circuit and basic structure for more feasible device. According to the experimental results on a dot-type braille block, a target level of the maximum plantar pressure was clarified. On the basis of these results, we designed a unit for the haptic device on feet.

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  • Measurement of plantar pressure and development of prototype for haptic device on sole of foot with magnetic field sensitive elastomer 査読

    Takehito Kikuchi, Yasunobu Masuda, Masao Sugiyama, Tetsu Mitsumata, Suguru Ohori

    Proceedings of the IEEE RAS and EMBS International Conference on Biomedical Robotics and Biomechatronics   1188 - 1193   2012年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    A magnetic field sensitive elastomer (MSE) is a compound of magnetic particles and non-magnetic elastomers. This is a functional material whose elasticity can be adjusted with an external magnetic field. The final goal of this study is to develop a virtual walking system using a haptic device on soles of feet with the MSE. First, we measured the difference of planter pressures when subjects (3 young healthy students) stepped on two different types of floor (dot-type braille block and flat floor). The differences of the normalized pressures were about 24, and these values are one of the development goal of the device. Next, we designed an electromagnet and evaluate the difference of plantar pressure with/without magnetic field on the MSE. According to the results, the difference of the normalized pressure depended on the weight of subjects. The difference of the normalized pressure was 2.3 for a light subject. However, there were not clear differences for heavier subjects. We should consider the basic elasticity of the MSE to develop a practical device. © 2012 IEEE.

    DOI: 10.1109/BioRob.2012.6290673

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  • Giant and reversible magnetorheology of carrageenan/iron oxide magnetic gels 査読

    Tetsu Mitsumata, Noriyuki Abe

    SMART MATERIALS & STRUCTURES   20 ( 12 )   2011年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    The effect of magnetic fields on the viscoelastic properties, the magnetorheological effect, of carrageenan gel containing iron oxide particles has been investigated using dynamic viscoelastic measurements under magnetic fields. The carrageenan concentration was varied in order to prepare magnetic gels with various storage moduli. Significant change in the storage modulus was not observed when the carrageenan concentration was 2 wt%; however, the magnetorheological effect appeared on decreasing the concentration. The maximum change in the relative storage modulus was 24 when the carrageenan concentration was 0.6 wt%. The loss tangents of the magnetic gels also altered in response to the magnetic field as well as the storage moduli. The relationship between the magnetorheology and the elasticity of magnetic gel is discussed.

    DOI: 10.1088/0964-1726/20/12/124003

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  • Magnetorheological behaviour of magnetic carrageenan gels against shear and compression strains 査読

    Keisuke Negami, Tetsu Mitsumata

    E-POLYMERS   2011年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WALTER DE GRUYTER GMBH  

    Magnetic field effect on the elasticity was investigated for magnetic carrageenan gel when a shear and compressional deformation was applied to the gel. The magnetic carrageenan gel consists of carrageenan of a polysaccharide, and carbonyl iron particles. The dynamic viscoelastic measurement with shear strain revealed that the storage shear modulus of the gel increased from 1.0x10(4) to 2.3x10(6) Pa by applying a magnetic field of 320 mT. On the other hand, the compression measurement showed that the Young's modulus increased from 6.2x10(4) to 5.9x10(5) Pa. The relative changes in the modulus with respect to the original modulus were 230 for shear strain and 9.5 for compressional strain, respectively. This strongly indicates that the magnetic field effect on viscoelasticity strongly depends on the geometry of directions of magnetic field and strain. The effect of vibration suppression of the present gel tuned by magnetic field is also presented.

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  • Magnetic polyurethane elastomers with wide range modulation of elasticity 査読

    Tetsu Mitsumata, Suguru Ohori

    POLYMER CHEMISTRY   2 ( 5 )   1063 - 1067   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    A new magnetorheological elastomer that demonstrates drastic and reversible changes in dynamic modulus in air was obtained. The magnetic elastomer consists of polyurethane and carbonyl iron particles. The magnetic elastomer with a volume fraction of 0.29 exhibited a reversible increase by factors of 277 of the storage modulus and 96 of the loss modulus upon a magnetic field of 500 mT. The elastomer underwent high mechanical toughness with a braking strain exceeding 0.8, and demonstrates the giant magnetorheological behavior for half a year after the synthesis without degradation.

    DOI: 10.1039/c1py00033k

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  • Gelation Behavior by the Lanthanoid Adsorption of the Cyanobacterial Extracellular Polysaccharide 査読

    Maiko K. Okajima, Toshimitsu Higashi, Ryuya Asakawa, Tetsu Mitsumata, Daisaku Kaneko, Tatsuo Kaneko, Tetsuya Ogawa, Hiroki Kurata, Seiji Isoda

    BIOMACROMOLECULES   11 ( 11 )   3172 - 3177   2010年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    The self-organization behavior of an extracellular polysaccharide (sacran) extracted from the cyanobacterium Aphanothece sacrum in response to lanthanoid ion adsorption was investigated. Consequently, cryogenic TEM images revealed that sacran could be cross-linked by Nd(3+) trivalent ions and formed a fibrous nanostructural network containing water. Furthermore, sacran adsorbed trivalent metal ions at a 3: 1 ratio, which was the theoretical ionic adsorption and showed more efficient adsorption than alginate based on electric conductivity titration. The critical gelation concentrations. C(g), where sacran formed tough gels upon metal ion binding were estimated. The C(g) for trivalent metal ions was lower than that for divalent ions, and the C(g) for lanthanoid ions was particularly low at 10(-3) to 10(-4) M, changing every four elemental numbers. The extracellular matrix of Aphanothece sacrum, sacran, may adsorb metal ions to create fibrous nanostructures that reinforce the jelly matrix.

    DOI: 10.1021/bm101012u

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  • Cyanobacterial Polysaccharide Gels with Efficient Rare-Earth-Metal Sorption 査読

    Maiko K. Okajima, Masatoshi Nakamura, Tetsu Mitsumata, Tatsuo Kaneko

    BIOMACROMOLECULES   11 ( 7 )   1773 - 1778   2010年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    The cyanobacterial polysaccharide sacran, which contains carboxylate and sulfate groups, was extracted from Aphanothece sacrum, and the metal sorption behavior of sacran was investigated. Heterogels, where the sacran chains were trapped by polyvinyl alcohol networks, were prepared and immersed in NdCl(3) solutions to shrink and cloud due to Nd binding. These heterogels had the ability to sorb excessive amounts of Nd ions, more than the stoichiometric ratio of 1:3 (sacran anion/Nd). Furthermore, the sacran-containing gels sorbed Nd ions under highly acidic conditions below pH 2 more efficiently than alginate-containing gels. We speculated that the strong Nd condensation effect of the sulfate groups in sacran under the acidic conditions may enhance the Nd sorption to the carboxylate groups.

    DOI: 10.1021/bm100231q

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  • Magnetorheology of Magnetic Poly(vinyl alcohol) Gels with High Mechanical Toughness 査読

    Keisuke Negami, Tetsu Mitsumata

    CHEMISTRY LETTERS   39 ( 6 )   550 - 551   2010年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    A magnetic-field-sensitive gel that demonstrates both drastic changes in dynamic modulus and high mechanical toughness was obtained. The magnetic gel consists of cross-linked poly(vinyl alcohol) (PVA), iron oxide particles, and water. The storage and loss shear moduli of the magnetic gel remarkably increased by applying a magnetic field, similarly to magnetic carrageenan gels. Compression revealed high mechanical toughness of the magnetic PVA gel and the maximum strain of 0.64 was achieved without inducing permanent strain.

    DOI: 10.1246/cl.2010.550

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  • Magnetic-field Sensitive Gels with Wide Modulation of Dynamic Modulus 査読

    Tetsu Mitsumata, Noriyuki Abe

    CHEMISTRY LETTERS   38 ( 9 )   922 - 923   2009年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    A new class of magnetorheological gel that demonstrates drastic and reversible changes in dynamic modulus without using strong magnetic fields was obtained. The magnetic gel consists of carrageenan of polysaccharides and carbonyl iron particles. The magnetic gel with a volume fraction of 0.34 exhibited a reversible increase by factors of 500 of the storage modulus and 1200 of the loss modulus upon a magnetic field of 500 mT. We Postulate that the particle structural change by magnetic fields leads to the drastic change in the dynamic modulus.

    DOI: 10.1246/cl.2009.922

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  • Recent progress in magnetorheological gels and elastomers 査読

    Tetsu Mitsumata

    Recent Patents on Chemical Engineering   2 ( 2 )   159 - 166   2009年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Magnetorheological gels and elastomers demonstrate the phenomenon that viscoelastic properties such as elastic modulus change in response to magnetic fields. The magnetorheological materials consist of polymeric matrices and magnetic particles. As the viscoelastic properties can be controlled by the magnetic field, the materials have been used for active dampers that are able to control the attenuation of vibration. The magnetic effect on the elastic modulus has been extensively improved for the last ten years. This review is a short survey of past investigations and patents on magnetorheological gels and elastomers, and presents feature problems of the materials. © 2009 Bentham Science Publishers Ltd.

    DOI: 10.2174/1874478810902020159

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  • Cyanobacteria That Produce Megamolecules with Efficient Self-Orientations 査読

    Maiko K. Okajima, Daisaku Kaneko, Tetsu Mitsumata, Tatsuo Kaneko, Junji Watanabe

    MACROMOLECULES   42 ( 8 )   3057 - 3062   2009年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    Liquid crystallization of structural megamolecules in plants is very significant in understanding of biopolymer self-orientation and developing plant-derived functional materials. Cyanobacterial megamolecules, sacrans (molecular weight: 1.6 x 10(7) g/mol), are polysaccharides derived from the extracellular matrix of Aphanothece sacrum, and are observed as self-orienting micro rods longer than 3 mu m in dilute solution at c = 0.01 wt % by optical microscopes. Sacran chains form double helixes at c > 0.09 wt % and form huge domains (centimeter scale) of liquid crystals at c > 0.5 wt % which is quite low when compared to conventional liquid crystalline polysaccharides. Mesogenic helical chains of sacrans have extremely high aspect ratios of 1600 for highly persistent lengths of 32 mu m.

    DOI: 10.1021/ma802829x

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  • Effect of Particles Alignment on Giant Reduction in Dynamic Modulus of Hydrogels Containing Needle-Shaped Magnetic Particles 査読

    Tetsu Mitsumata, Yuhei Kosugi, Shunsuke Ouchi

    GELS: STRUCTURES, PROPERTIES, AND FUNCTIONS   136   163 - +   2009年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPRINGER-VERLAG BERLIN  

    We investigated the giant reduction in the dynamic modulus of magnetic gels with aligned particles. The magnetic gel is consisting of a kappa-carrageenan gel loaded with gamma-Fe2O3 particles with an aspect ratio of similar to 8. The magnetic particles were aligned by a weak magnetic field of 50 mT during gelation. The gels with aligned particles demonstrated giant reductions in the storage Young's modulus on the order of 10(6) Pa due to magnetization; however, no reductions in the storage modulus were observed for the gels with random particles. The storage modulus of gels with aligned particles did not follow the Halpin-Tsai equation above volume fractions of 0.01, indicating the heterogeneous dispersion of the magnetic particles; however, the modulus of the gels with random particles satisfied the equation at all volume fractions, suggesting the random dispersion of the particles. It was noted that the gels with aligned particles demonstrated enhanced nonlinear viscoelasticity and a large value of the loss tangent, while the gels with random particles exhibited weak nonlinear viscoelasticity and a small value of the loss tangent. This indicates that the magnetic particles form a particle network in the gel with aligned particles. It was also found that the magnetic gel with aligned particles did not undergo a marked reduction in the storage modulus when the magnetic field was applied in parallel with the alignment of magnetic particles. This strongly indicates that the giant reduction in dynamic modulus is caused by breaking the particle network developed in the magnetic gel.

    DOI: 10.1007/2882_2009_23

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  • Particle Dispersibility and Giant Reduction in Dynamic Modulus of Magnetic Gels Containing Barium Ferrite and Iron Oxide Particles 査読

    Tetsu Mitsumata, Takashi Wakabayashi, Takahiko Okazaki

    JOURNAL OF PHYSICAL CHEMISTRY B   112 ( 45 )   14132 - 14139   2008年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    The particle dispersibility of barium ferrite and iron oxide magnetic particles in carrageenan gels was investigated, and the influence of the dispersibility on the giant reduction in the dynamic modulus of the gels was discussed. The gels containing barium ferrite demonstrated giant reductions in the storage Young's modulus on the order of 10(5) Pa due to magnetization; however, small reductions in the storage modulus of less than 10(4) Pa were observed for the gels containing iron oxide. The storage modulus of gels with barium ferrite did not follow the Krieger-Dougherty equation above volume fractions of 0.06, indicating the heterogeneous dispersion of the magnetic particles; however, the modulus of the gels with iron oxide satisfied the equation at all volume fractions, suggesting the random dispersion of the particles. It was noted that the gels with barium ferrite demonstrated enhanced nonlinear viscoelasticity and a large value of the loss tangent, while the gels with iron oxide exhibited weak nonlinear viscoelasticity and a small value of the loss tangent. Magnetic measurements indicated high values of remanent magnetization for barium ferrite and low values for iron oxide. After magnetization at 1 T, the magnetic gels with barium ferrite became elongated parallel to the magnetic field and shrunk perpendicular to the field. In contrast, the magnetic gels with iron oxide did not undergo a marked deformation. These results strongly indicate that the giant reduction in the storage modulus requires both enhanced nonlinear viscoelasticity and magnetostriction which originate from the particle dispersibility. The relationship between the dispersibility of magnetic particles and the giant reduction in the storage modulus is discussed using theological and morphological data.

    DOI: 10.1021/jp805955j

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  • High-power actuators made of two-phase magnetic gels 査読

    Tetsu Mitsumata, Yuki Horikoshi, Keisuke Negami

    JAPANESE JOURNAL OF APPLIED PHYSICS   47 ( 9 )   7257 - 7261   2008年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:JAPAN SOCIETY APPLIED PHYSICS  

    The magnetic field-induced elongation of magnetic gels consisting of poly(vinyl alcohol) (PVA) and magnetic particles was analyzed. The elongation increased as the concentration of magnetic particles increased, and inversely it decreased as the cross-linking density increased. We propose a simple theoretical expression of the elongation taking into consideration the elastic modulus of magnetic gels. We have fabricated a high-power actuator made of magnetic gels consisting of a thin magnetic-gel phase and a thick PVA-gel phase. A maximum strain of 33% was achieved while sustaining a constant stress of 1.3 kPa using a magnetic field of 900 mT. The magnetic gel showed a maximum stress of 6.8 kPa and a strain of approximately 10%. Magnetic gels consisting of two gel phases have great potential for application in practical actuators that can be driven by a magnetic field.

    DOI: 10.1143/JJAP.47.7257

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  • Nonlinear viscoelasticity, percolation and particles dispersibility of PVA/aluminum hydroxide composite gels 査読

    Tetsu Mitsumata, Tomohiro Hachiya, Koji Nitta

    EUROPEAN POLYMER JOURNAL   44 ( 8 )   2574 - 2580   2008年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    We investigated the rheological properties of a composite gel consisting of poly(vinyl alcohol) and aluminum hydroxide particles, and discussed the relation among nonlinear viscoelasticity, percolation and particles dispersibility. The dynamic viscoelastic measurements revealed that the storage modulus at volume fractions phi < 0.04 satisfied with the Krieger-Dougherty equation representing random dispersion of particles. The storage modulus did not show any nonlinear viscoelastic response at 0 < 0.04. However, the storage modulus at phi > 0.06 took a value which is far larger than that expected by the equation, indicating heterogeneous distribution of particles. Additionally, the nonlinear viscoelastic response was recognized clearly at 0 > 0.06, suggesting a partial contact between particles. The storage modulus at phi > 0.18 showed a further increase satisfied with the percolation theory, therefore, the volume fraction is considered to be the percolation threshold of 3-dimension. Microscopic observations of the gel showed a clear network with a mesh size of few mu m that is considered to be a partial network of particles. (C) 2008 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.eurpolymj.2008.06.009

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  • Swelling and viscoelastic properties of poly(vinyl alcohol) physical gels synthesized using sodium silicate 査読

    Tetsu Mitsumata, Chikako Hasegawa, Hiroyuki Kawada, Tatsuo Kaneko, Jun-Ichi Takimoto

    REACTIVE & FUNCTIONAL POLYMERS   68 ( 1 )   133 - 140   2008年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    A physically crosslinked poly(vinyl alcohol) (PVA) gel was synthesized from mixed aqueous solutions of PVA and sodium silicate (SS) using freeze/thaw techniques. The infrared spectroscopy, swelling and viscoelastic properties of the resultant gel have been investigated. The infrared spectrum of the resultant gel was as in the spectrum of PVA gel without SS. The resultant gel showed that the absorbing band due to stretching of hydroxyl groups shifted to a lower wave number, indicating the enhancement of hydrogen bonding between hydroxyl groups in PVA. Dynamic viscoelastic measurements showed that the storage modulus of the resultant gel was 1 order of magnitude higher than that of PVA gel without SS. The degree of swelling Q varied with the SS concentration c(SS) as Q similar to c(SS)(-1) (0.12 < v < 0.37). The storage modulus at 1 Hz E' changed by the degree of swelling Q satisfying with a power low as E' similar to Q(-3.8). Microphotographs of the gels in a dry state showed that PVA network developed extensively as increasing the SS concentration. These results obtained strongly indicate that the resultant gel consists from only PVA, not composites of PVA and SS. It can be considered that SS hastens the aggregation or crosslinking of PVA chains; as a result physically crosslinked gels with close network and high elasticity were obtained. Reswelling experiment showed that the degree of swelling by the reswelling for the resultant gel was approximately 10, which was less than 1/6 of the original value of the degree of swelling. (C) 2007 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.reactfunctpolym.2007.10.003

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  • Analysis for the Elongational Motion of PVA Magnetic Gels Under Gradient Magnetic Fields 査読

    Yuki Horikoshi, Tetsu Mitsumata, Jun-ichi Takimoto

    TRANSACTIONS OF THE MATERIALS RESEARCH SOCIETY OF JAPAN, VOL 33, NO 2   33 ( 2 )   435 - 437   2008年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:MATERIALS RESEARCH SOCIETY JAPAN-MRS-J  

    We have investigated the elongational motion of magnetic gels under gradient magnetic fields. The magnetic gel was made from fine particles of iron oxide and a network of poly(vinyl alcohol) crosslinked by glutaraldehyde. The elongation increased with increasing the magnetic field strength up to 1200 mT. The elongation increased as increasing the concentration of magnetic particles; oppositely, it decreased as increasing the crosslinking density. It was found that the elongation can be explained by a classical theory of magnetism that the elongation is proportional to the product of magnetization and the field gradient. The effect of load on the elongation has been also investigated. The coefficient of the conversion from magnetic energy to mechanical one was estimated to be 10(-4)%, which is nearly independent of the load.

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  • Electric Properties of Ionic Polysaccharide Sacran Aqueous Solutions 査読

    Tetsu Mitsumata, Maiko Okajima-Kaneko, Tatsuo Kaneko

    TRANSACTIONS OF THE MATERIALS RESEARCH SOCIETY OF JAPAN, VOL 33, NO 2   33 ( 2 )   431 - 434   2008年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:MATERIALS RESEARCH SOCIETY JAPAN-MRS-J  

    We have investigated the electric conductivity and dielectric constant of an aqueous solution of polysaccharide, Aphanothece sacrum, that is called sacran. The molar conductivity at high concentrations obeyed Kohlrausch's law. The equivalent conductivity at infinite dilution was in good agreement with that of Na(+) ion in an aqueous solution. The complex dielectric constant epsilon* of the aqueous solutions was measured from 42 Hz to 5 MHz by an ac two-terminals method. The dielectric spectra of the aqueous solutions after subtracting the electrode polarization effect could be fitted by two Debye type relaxations. The low frequency relaxation and high frequency one appeared at 100 Hz and 100 kHz, respectively. The low frequency relaxation time for the aqueous solution of 2.0x10(-3) wt.% was determined to be 2.1 x10(-3) s. The contour length of the sacran was estimated to be similar to 5.5 mu m using the diffusion constant of Na(+) ion in a free medium. This value was in the same magnitude with the length evaluated from transmission electron microscopy and static light scattering experiments.

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  • Fast drug release using rotational motion of magnetic gel beads 査読

    Tetsu Mitsumata, Yusuke Kakiuchi, Jun-Ichi Takimoto

    Research Letters in Physical Chemistry   2008   5   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Accelerated drug release has been achieved by means of the fast rotation of magnetic gel beads. The magnetic gel bead consists of sodium alginate crosslinked by calcium chlorides, which contains barium ferrite of ferrimagnetic particles, and ketoprofen as a drug. The bead underwent rotational motion in response to rotational magnetic fields. In the case of bead without rotation, the amount of drug release into a phosphate buffer solution obeyed non-Fickian diffusion. The spontaneous drug release reached a saturation value of 0.90 mg at 25 minutes, which corresponds to 92% of the perfect release. The drug release was accelerated with increasing the rotation speed. The shortest time achieving the perfect release was approximately 3 minutes, which corresponds to 1/8 of the case without rotation. Simultaneous with the fast release, the bead collapsed probably due to the strong water flow surrounding the bead. The beads with high elasticity were hard to collapse and the fast release was not observed. Hence, the fast release of ketoprofen is triggered by the collapse of beads. Photographs of the collapse of beads, time profiles of the drug release, and a pulsatile release modulated by magnetic fields were presented.

    DOI: 10.1155/2008/671642

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  • Flexible fluid pump using magnetic composite gels 査読

    Tetsu Mitsumata, Yuki Horikoshi, Jun-Ichi Takimoto

    E-POLYMERS   2007年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:EUROPEAN POLYMER FEDERATION  

    A flexible fluid pump made of magnetic composite gels has been developed. The magnetic composite gel was sodium alginate or poly(vinyl alcohol) gel in which barium ferrite particles were dispersed. The pump consisted of a magnetic gel- rotor and a driving magnet. The rotor demonstrated the rotational motion in response to a rotational magnetic field generated by the driving magnet. The gel- rotor had the shape of a screw so as to deliver water efficiently. The diameter of the rotor was varied from 3.8 to 5.5 mm and the diameter of the tube for delivering water was kept as 6 mm. Flow rates pumped by the rotor increased with increasing the diameter, length, and rotation speeds of the rotor. The maximum flow rate of 34 ml/min was achieved when the rotation speeds was 5000 rpm. The rotor with a diameter of 300 mu m was also successfully synthesized, however the rotor did not deliver water in a microtube with a diameter of 500 mu m. Processing of the gel- rotor, and the efficiency of the water delivery are presented.

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  • Magnetization-induced reduction in dynamic modulus of polyurethane Elastomers loaded with ferrite 査読

    Tetsu Mitsumata, Takahiko Okazaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS   46 ( 7A )   4220 - 4224   2007年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:INST PURE APPLIED PHYSICS  

    Magnetization effects on the dynamic modulus of a magnetic elastomer consisting of polyurethane and barium ferrite have been investigated. The complex modulus was measured before and after magnetization by dynamic viscoelastic measurements with a compressional strain. Giant reductions in storage modulus of similar to 105 Pa and in loss modulus of similar to 104 Pa were observed after magnetizing the elastomer at 1 T. The magnetic elastomer also showed a deformation with a strain of similar to 10-4 caused by the magnetization. The observed giant reduction in dynamic modulus can be ascribed to the large nonlinear viscoelastic response of the magnetic elastomer and the magnetization-induced deformation. Nonlinear viscoelastic responses, morphologies of magnetic particles, and deformation for the magnetic elastomer are discussed.

    DOI: 10.1143/JJAP.46.4220

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  • Thermosensitive solutions and gels consisting of poly(vinyl alcohol) and sodium silicate 査読

    Tetsu Mitsumata, Hiroyuki Kawada, Jun-ichi Takimoto

    MATERIALS LETTERS   61 ( 18 )   3878 - 3881   2007年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    We have investigated the transparency for visible light of a poly(vinyl alcohol) (PVA) aqueous solution in the presence of sodium silicates (SS). The transparency of the aqueous solution dramatically changed by varying temperature despite that neither aqueous solutions of PVA nor SS is sensitive to temperature. The aqueous solution showed a lower critical solution temperature (LCST) around 30 degrees C. The LCST depended on both concentrations of PVA and sodium silicate. Below the LCST, the transmittance was thermally irreversible. By a further increase in the temperature, the solution was separated into two phases consisting of a phase rich in solvent and that in solute; that is a coacervation. In the region of coacervation, the transmittance was thermally reversible. Reversible change in the transmittance was realized corresponding to stepwise temperature changes between 10 and 40 degrees C. A PVA gel swollen by the solution demonstrated transparency change in response to temperature changes as well as the solution. (C) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.matlet.2006.12.051

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  • Storage modulus of poly( vinyl alcohol) gels loaded with polyelectrolyte particles 査読

    Tetsu Mitsumata, Mitsuaki Nagata, Takashi Taniguchi, Seigou Kawaguchi

    E-POLYMERS   2007年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:EUROPEAN POLYMER FEDERATION  

    We have investigated the viscoelastic properties of poly( vinyl alcohol) (PVA) gels loaded with a polyelectrolyte particle of poly(styrene-co-sodium styrene sulfonate) to find the effect of electric charges on the storage modulus of the gel. The storage modulus decreased with increasing volume fraction of particles, and it was independent of the strain, indicating linear viscoelasticity. The viscoelastic properties of PVA gels containing non-charged particles of aluminium hydroxides were also studied. While the degree of swelling kept a constant value, the storage modulus largely increased with the volume fraction. PVA gels containing non-charged particles underwent a large nonlinear viscoelastic response suggesting the particles connect each other in the gel. Viscoelastic properties of the PVA gel loaded with charged and non-charged particles have also been discussed.

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  • Giant magnetorheological effect of agar magnetic gels 査読

    Tetsu Mitsumata, Takafumi Yamamoto, Emiko Suzuki, Jun-ichi Takimoto

    TRANSACTIONS OF THE MATERIALS RESEARCH SOCIETY OF JAPAN, VOL 32, NO 3   32 ( 3 )   811 - 814   2007年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:MATERIALS RESEARCH SOCIETY JAPAN-MRS-J  

    Effects of matrix on the giant reduction in storage modulus of magnetic gels have been investigated using agar and carrageenan gels. The complex modulus was measured before and after magnetization of the gel by dynamic viscoelastic measurements with a compressional strain. The agar magnetic gels showed a large nonlinear viscoelastic response and magnetically-induced deformation. The giant reduction in the storage modulus of similar to 10(5) Pa, and also in the loss modulus of similar to 10(4) Pa was observed for agar magnetic gels, as well as carrageenan one. The deformation due to magnetization seen in agar magnetic gels was larger than that in carrageenan by more than twice. Rheological data, deformation due to magnetization, and morphologies of magnetic particles have been discussed.

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  • Developments for a fluid valve using magnetic gels 査読

    Yuki Horikoshi, Tetsu Mitsumata, Jun-ichi Takimoto

    TRANSACTIONS OF THE MATERIALS RESEARCH SOCIETY OF JAPAN, VOL 32, NO 3   32 ( 3 )   843 - 844   2007年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:MATERIALS RESEARCH SOCIETY JAPAN-MRS-J  

    We have fabricated the fluid valve in a fluid tube of 800 pm in diameter using magnetic gels. The magnetic gel was made from a network of poly(vinyl alcohol) crosslinked by glutaraldehyde and fine particles of iron oxide. When a weak magnetic field was applied to the valve, the valve came into a microtube and, as a result, a flow of water stopped. The valve opened and closed in response to the magnetic field generated by a permanent magnet. The valve worked well under the pressures of water from 0.3 MPa to 1.6 MPa.

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  • Giant reduction in dynamic modulus of kappa-carrageenan magnetic gels 査読

    Tetsu Mitsumata, Kazuki Sakai, Jun-ichi Takimoto

    JOURNAL OF PHYSICAL CHEMISTRY B   110 ( 41 )   20217 - 20223   2006年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    Effects of magnetization on the complex modulus of kappa-carrageenan magnetic gels have been investigated. The magnetic gel was made of a natural polymer, kappa-carrageenan, and a ferrimagnetic particle, barium ferrite. The complex modulus was measured before and after magnetization of the gel by dynamic viscoelastic measurements with a compressional strain. The gels showed a giant reduction in the storage modulus of similar to 10(7) Pa and also in the loss modulus of similar to 10(6) Pa due to magnetization. The reduction increased with increasing volume fraction of ferrite, and it was nearly independent of the frequency. It was also found that the change in the modulus was nearly independent of the magnetization direction and irradiation time of the magnetic fields to the gel. The magnetic gels demonstrating the giant reduction in the dynamic modulus showed a large nonlinear viscoelastic response. It was observed that the magnetic gel was deformed slightly due to magnetization. The observed giant complex modulus reduction could be attributed to the nonlinear viscoelasticity and deformation caused by magnetization. Magnetism, nonlinear viscoelasticity, and effects of magnetization on the morphological and shape changes were discussed.

    DOI: 10.1021/jp063494g

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  • Anisotropy in elastic modulus of hydrogel containing magnetic particles 査読

    Takashi Taniguchi, Tetsu Mitsumata, Masataka Sugimoto, Kiyohito Koyama

    PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS   370 ( 2 )   240 - 244   2006年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    We derive the analytic expression of elastic modulus for a gel containing magnetic particles with a magnetic dipole moment. The obtained elastic modulus is anisotropic and the modulus increases and decreases with the density of magnetic particle when the direction of strain is perpendicular and parallel to the direction of magnetization, respectively. This behavior is qualitatively in good agreement with previous experimental data [T. Mitsumata, et al., Macromol. Rapid Commun. 23, (2002) 178]. (c) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physa.2006.02.040

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  • Microstructural evolution of electrically activated polypropylene/layered silicate nanocomposites investigated by in situ synchrotron wide-angle X-ray scattering and dielectric relaxation analysis 査読

    Do Hoon Kim, Kwang Soo Cho, Tetsu Mitsumata, Kyung Hyun Ahn, Seung Jong Lee

    POLYMER   47 ( 16 )   5938 - 5945   2006年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCI LTD  

    Electric field was found to facilitate the destruction of layer stacking and separation of silicate layers in polypropylene (PP)/layered silicate nanocomposites, resulting in the penetration of polymer chains into silicate galleries. In this study, we describe the real-time microstructural evolution of PP/clay nanocomposites under electric field investigated by in situ synchrotron wide-angle X-ray scattering (WAXS) analysis. We were able to identify two distinctive mechanisms for the formation of nanocomposites depending on the type of electric field. We observed that the exfoliation process prevails in the AC field, while the alignment of silicates parallel to the electric field predominates in the DC field. Dielectric relaxation analysis showed that the different mechanisms originate from different charge distributions of bound ions attached to the clay surfaces due to the applied electric field. (c) 2006 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.polymer.2006.06.029

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  • Microwave enhancement of elasticity in poly(propylene)-carbon nanotube composites 査読

    S Yoshida, T Mitsumata, M Sano

    CHEMISTRY LETTERS   35 ( 3 )   262 - 263   2006年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    Irradiating weak microwave to a poly(propylene) composite containing a small amount of single-walled carbon nanotubes (SWCNTs) enhances the storage modulus but has no effect on the loss modulus. We postulate that local melting and recrystallization of the polymer in the close vicinity of the SWCNT surface lead to better wetting, and larger contact areas for the improved elastic response.

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  • Developments for a fluid pump using magnetic gels 査読

    Tetsu Mitsumata, Yuki Horikoshi, Jun-ichi Takimoto

    TRANSACTIONS OF THE MATERIALS RESEARCH SOCIETY OF JAPAN, VOL 31, NO 3   31 ( 3 )   803 - 805   2006年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:ELSEVIER SCIENCE BV  

    We have developed a fluid pump using magnetic hydrogels synthesized by ferromagnetic fine particles and natural polymers. The pump is mainly consisted of a rotor made of the magnetic gel and a driving magnet. The driving magnet drives the rotor in a fluid tube without any physical contact. The rotor of the fluid pump rotates corresponding to the rotation rates of the driving magnet. The shape of the rotor was a screw so as to deliver water easily. Diameters of the rotor and the tube for delivering water were approximately 5.5mm and 6mm, respectively. Flow rates pumped by the rotor increased with increasing diameter, length of the rotor, and rotation rates. The maximum flow rates of 34 ml/min was achieved when the rotation rates was 5000 rpm. Factors affecting the flow rate of water will be presented.

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  • Rheological characteristics and magnetization effects of magnetic gels 査読

    Tetsu Mitsumata, Kazuki Sakai, Jun-ichi Takimoto

    Transactions of the Materials Research Society of Japan, Vol 31, No 3   31 ( 3 )   807 - 810   2006年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:ELSEVIER SCIENCE BV  

    Magneto-rheological effects of K-carrageenan magnetic gels have been investigated. The magnetic gel was made of a natural polymer of K-carrageenan and a ferromagnetic particle of barium ferrite. The complex modulus of the magnetic gel was measured by dynamic viscoelastic measurements with a compressional strain. It was observed that the magnetic gels showed giant storage modulus reduction similar to 10MPa before and after magnetization. The reduction increased with increasing the volume fraction of the ferrite and it reached 14.9 MPa at maximum. No volume change was observed during magnetization. Strain and frequency dependences of the dynamic modulus and a possible mechanism of the modulus reduction have been discussed.

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  • Giant complex modulus reduction of kappa-carrageenan magnetic gels 査読

    T Mitsumata, A Nagata, K Sakai, J Takimoto

    MACROMOLECULAR RAPID COMMUNICATIONS   26 ( 19 )   1538 - 1541   2005年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

    Effects of magnetization on the complex modulus of kappa-carrageenan magnetic gels have been investigated. The magnetic gel was made of a natural polymer, kappa-carrageenan, and a ferromagnetic particle, barium ferrite. The complex modulus of the magnetic gel was investigated by dynamic viscoelastic measurements with a compressional strain. It was first observed that the magnetic gels showed giant storage modulus reduction;approximate to 10(7) Pa before and after magnetization. The reduction was nearly independent of the frequency, and it increased with increasing the volume fraction of the ferrite. The maximum reduction in the storage modulus reached 14.9 MPa which corresponds to 76.5% of the modulus before magnetization. It was also found that the change in the modulus was nearly independent of a magnetization direction. Magnetism and morphology of the magnetic gels were also presented.

    DOI: 10.1002/marc.200500405

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  • Morphology-rheology relationship in hyaluronate/poly(vinyl alcohol)/borax polymer blends 査読

    SH Kim, K Hyun, TS Moon, T Mitsumata, JS Hong, KH Ahn, SJ Lee

    POLYMER   46 ( 18 )   7156 - 7163   2005年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCI LTD  

    In this work, we have prepared bioartificial polymer blends using hyahuronate (HA) as a biological component and poly(vinyl alcohol)borax association (PVAs) as a synthetic component, and investigated the rheological properties as well as morphology of the blends. When plotted against the blend composition. the rheological properties showed both positive and negative deviation from the linear additive mixing rule depending on thermal history. The blend showed enhanced viscosity at the composition of 20 wt% of HA and 80 wt% of PVAs, when PVA was dissolved at high temperature. The viscosity enhancement was caused by the network formation of HA aggregates in the micrometer scale. In addition. the network Structure of HA aggregates was found to be fractal with the fractal dimension of 1.7. As PVA system also forms a network Structure in the nanometer scale between hydroxyl groups of PVA and borate anions, the blend system is unique in that it has network Structures in both micrometer and nanometer scales in one material. On the contrary. HA formed aggregates but not any network structure in the blend of the same composition but of the negative deviation. In Conclusion, we showed that HA/PVAs blend system may have diverse morphology as well its very broad spectrum of rheological properties, and could suggest that the rheology and morphology of HA/PVAs blends can be designed not only by controlling composition but also by controlling thermal and deformation history of the components. (c) 2005 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.polymer.2005.05.089

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  • Anisotropy in storage modulus of magnetic gels induced by magnetization

    Tetsu Mitsumata, Akiyasu Nagata, Kazuki Sakai, Takashi Taniguchi

    Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers   43 ( 12 )   8203 - 8207   2004年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The effects of magnetization direction on the complex modulus of magnetic gels, which consist of magnetized barium ferrite and poly vinyl alcohol, have been investigated. The modulus after magnetization showed anisotropy depending on the geometry of magnetization and strain direction. It was also confirmed that the modulus change occurred without volume change. This strongly suggested that the modulus change of magnetic gels originates not from a decrease in the volume of the magnetic gels but from the magnetic dipole interactions between ferrites dispersed in the gels.

    DOI: 10.1143/JJAP.43.8203

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  • Electrorheological response of swollen silicone gels containing barium titanate 査読

    T Mitsumata, K Sugitani, K Koyama

    POLYMER   45 ( 11 )   3811 - 3817   2004年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCI LTD  

    We have investigated storage moduli of silicone gels containing barium titanate in the presence of dc electric fields. The gels containing barium titanate swollen by silicone oil showed a storage modulus reduction, i.e. negative electrotheological effect. Contrary, no negative electrorheological effect was observed in the unswollen gels and silicon gels without barium titanate. Swollen silicone gels and most of silicone/BaTiO3 gels obeyed empirical quadratic dependence in electric field strength. Although an apparent phase separation was not observed in the swollen gel, microscopic phase separation may occur due to the difference in electric conductivity between particles (similar to10(-10) S/cm) and silicone oil (10(-9) S/cm), as a result, the negative electrotheological effect appears. The effects of frequency, degree of swelling, and the field strength have been discussed. (C) 2004 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.polymer.2004.03.056

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  • Negative electrorheological effect of silicone gels containing barium titanate 査読

    T Mitsumata, K Sugitani

    MACROMOLECULAR RAPID COMMUNICATIONS   25 ( 8 )   848 - 852   2004年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

    We observed the negative electrorheological phenomenon on swollen silicone gels containing barium titanate. Contrary,no negative electrorheological effect was observed in unswollen silicone gels containing barium titanate and silicon gels without barium titanate. The change in storage modulus increase with increasing DC electric field strength. The effects of frequency, degree of swelling, and the field strength have been investigated.

    DOI: 10.1002/marc.200300278

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  • pH-response of chitosan, κ-carrageenan, carboxymethyl cellulose sodium salt complex hydrogels 査読

    Tetsu Mitsumata, Yuuki Suemitsu, Keiko Fujii, Tomoyuki Fujii, Takashi Taniguchi, Kiyohito Koyama

    Polymer   44 ( 23 )   7103 - 7111   2003年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.polymer.2003.09.001

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  • Ultrasonic Investigations of Hydrogels Containing Barium Ferrite Particles 査読

    Etienne Juliac, Tetsu Mitsumata, Takashi Taniguchi, Kenji Iwakura, Kiyohito Koyama

    The Journal of Physical Chemistry B   107 ( 23 )   5426 - 5431   2003年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1021/jp027531p

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  • Storage modulus and surface morphology of poly(vinyl alcohol)/alumina hybrid hydrogels 査読

    T Mitsumata, M Yuge, S Morino, K Iwakura, K Koyama

    MACROMOLECULAR RAPID COMMUNICATIONS   23 ( 17 )   1045 - 1048   2002年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

    The storage moduli, shear moduli and surface morphologies of poly(vinyl alcohol) (PVA) and alumina hybrid hydrogels were investigated. The storage moduli of hybrid hydrogels with higher alumina contents were found to be 1.5 times higher than those of PVA gels. This increase in modulus might be attributed to the cohesion of alumina to the PVA network.

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  • Anisotropy in longitudinal modulus of polymer gels containing ferrite 査読

    T Mitsumata, E Juliac, K Furukawa, K Iwakura, T Taniguchi, K Koyoma

    MACROMOLECULAR RAPID COMMUNICATIONS   23 ( 3 )   175 - 178   2002年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

    The effects of magnetization direction on the longitudinal modulus of magnetic gels, which consist of magnetized barium ferrite and poly(vinyl alcohol), have been investigated using 10 MHz ultrasonic waves. The modulus change due to magnetization depends on both the crosslinking density and magnetization direction. The modulus change increased and decreased when the strain direction was perpendicular and parallel to magnetization, respectively.

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  • Shape memory functions and motility of amphiphilic polymer gels 査読

    Tetsu Mitsumata, Jian Ping Gong, Yoshihito Osada

    Polymers for Advanced Technologies   12 ( 1-2 )   136 - 150   2001年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:John Wiley and Sons Ltd  

    Amphiphilic polymer gels which can swell in both organic fluid and water have been widely investigated. We have discovered that this class of gels shows two special characteristics, i.e. the shape memory function and the spontaneous motion. The principle of the shape memory is based on a reversible order-disorder transition associated with interactions between the alkyl side chains of the stearyl acrylate units. This effect is completely different from the one of shape memory alloys. When the swollen gel is heated, its Young's modulus decreases by about three orders of magnitude, from 107 dyn/cm2 at 25°C to 104 dyn/cm2 at 50°C. These drastic changes in the mechanical properties enable the gel to show the shape memory function. Another feature of these gels is the spontaneous motion. The mechanism of the motion originates from the difference of surface tension between water and organic solvent that is pumped out by osmotic and hydrostatic pressures from the gel. Recently, we have succeeded to change the random motion to a translational one with a velocity of 77 mm/sec or rotational one with a maximum speed of 400 rpm. Motivated by this, electric power generator called "solvent-driven chemical motor" has been constructed. The generator produced an electric power with a maximum electromotive force of 15 mV and electric power of 0.2 μW. Copyright © 2001 John Wiley &amp
    Sons, Ltd.

    DOI: 10.1002/1099-1581(200101/02)12:1/2<136::AID-PAT76>3.0.CO;2-G

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  • Controlled motion of solvent-driven gel motor and its application as a generator 査読

    Tetsu Mitsumata, Kazuo Ikeda, Jian Ping Gong, Yoshihito Osada

    Langmuir   16 ( 2 )   307 - 312   2000年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ACS  

    Attempts have been made to control the spontaneous random motion of a tetrahydrofuran-swollen amphiphilic polymer gel on a water surface. By allowing the ejection of tetrahydrofuran through spouting holes, the gel showed an improved translational motion with a velocity of 77 mm/s or rotation with a rotation rate of 394 rpm. The controlled rotation showed an energy efficiency of 4.5×10-3%, which was 10 times of that of random motion. On the basis of the improved rotational motion of the gel, a generator consisting of a gel rotor equipped with a pair of permanent magnets and a solenoid coil has been constructed. The generator rotor which was 40 mm long, 6 mm wide, and 2 mm thick, produced an alternative electric power with an instantaneous electromotive force as high as 15 mV for a period of over 30 min. Such behaviors as the controlled motion, the spreading rate of tetrahydrofuran on the water surface, the crystallization and texture of gel surfaces, and the power generated have been described.

    DOI: 10.1021/la990483o

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  • Magnetism and compressive modulus of magnetic fluid containing gels 査読

    Tetsu Mitsumata, Kazuo Ikeda, Jian Ping Gong, Yoshihito Osada, Dénes Szabó, Miklós Zrínyi

    Journal of Applied Physics   85 ( 12 )   8451 - 8455   1999年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Institute of Physics Inc.  

    We have investigated the magnetism and have measured the compressive modulus of magnetic fluid containing gels, called ferrogels, in the presence of magnetic field. No hysteresis was shown in the magnetization curve of the ferrogel suggesting a super paramagnetic response. The equilibrium compressive modulus of the ferrogel was measured up to 4 kOe and the modulus with field was much higher than that without field. The mean change in modulus increased with increasing magnetic field, and it saturates above 2 kOe. The mean and maximum change in modulus at 4 kOe was 31 and 71 Pa which corresponds to 19% and 46% increases of that without field, respectively. The change in modulus has been analyzed theoretically and is well explained in terms of the magnetism of ferrogels. © 1999 American Institute of Physics.

    DOI: 10.1063/1.370626

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  • Dense Kondo compound Ce5Ge3 査読

    M. Kurisu, T. Mitsumata, I. Oguro

    Physica B: Condensed Matter   259-261   96 - 98   1999年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier  

    Magnetic and transport properties of Ce5Ge3 and La5Ge3 have been studied. The magnetic susceptibility of Ce5Ge3 above 90 K is fitted with a Curie-Weiss law with an effective paramagnetic moment of 2.66μB and a paramagnetic Curie temperature of - 30.9 K. Arrott plot shows that Ce5Ge3 has a spontaneous magnetization below 6.4 K. The magnetization curve shows large hysteresis with remanent magnetic moment of 0.24μB and coercive field of 1.2 kOe at 2.0 K. The magnetization at 1.9 K reaches 0.9μB/Ce at 145 kOe and saturation behavior is not found even at this high field. The temperature dependence of the magnetic resistivity indicates that Ce5Ge3 can be classified as a dense Kondo system. © 1999 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0921-4526(98)01041-2

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  • Solvent-driven chemical motor 査読

    Tetsu Mitsumata, Kazuo Ikeda, Jian Ping Gong, Yoshihito Osada

    Applied Physics Letters   73 ( 16 )   2366 - 2368   1998年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A solvent-driven chemical motor using amphiphilic polymer gel has been fabricated. The driving force of the gel originates from the surface tension of spreading organic fluid which is pumped out by osmotic and hydrostatic pressures in the gel. A tetrahydrofurane-swollen gel equipped with a spouting hole made a controlled translational motion with a velocity of 77 mm/s or rotational motion with a maximum speed of 400 rpm and a torque of 10-9-10-7Nm on the water surface. A generator to produce an electric power with a maximum electromotive force of 15 mV and electric power of 0.2 μW has also been constructed. The successful fabrication of gel motor may produce a new era of soft machine systems which work without pollution and unnecessary intermediates. © 1998 American Institute of Physics.

    DOI: 10.1063/1.122505

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共同研究・競争的資金等の研究

  • 液晶性多糖を用いた力学刺激によるイオン吸脱着システムの創製

    研究課題/領域番号:25620139  2013年4月 - 2015年3月

    日本学術振興会  科学研究費助成事業 挑戦的萌芽研究  挑戦的萌芽研究

    三俣 哲

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    配分額:4030000円 ( 直接経費:3100000円 、 間接経費:930000円 )

    サクランは光合成微生物藍藻から抽出される天然高分子である。ここではサクランの液晶のポリドメインの有無による粘度変化を調査した。サクラン1wt%水溶液は弱いゲル状で、室温、流動が無い状態では液晶のポリドメインを形成する。せん断速度1s-1以上では、定常流粘度が急激に低下するチキソトロピー挙動を示す。また、高速流動下ではポリドメインが崩壊しモノドメイン化する。反対に、せん断速度を遅くすると粘度が時々刻々と増加する負のチキソトロピー性を示すが、低速流動下でもポリドメインが崩壊しモノドメイン化する。動的粘弾性測定結果から、イオン吸着は鎖間架橋など、ミクロスケールで生じていると考えられる。

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  • やわらかさが瞬時に変化する高機能磁性ソフトマテリアルの創製と応用

    研究課題/領域番号:23360051  2011年4月 - 2014年3月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    三俣 哲

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    配分額:18070000円 ( 直接経費:13900000円 、 間接経費:4170000円 )

    永久磁石を近づけるとプリンのように軟らかかった状態が瞬時にプラスチックのように硬くなる新素材を開発した。ゴムのような樹脂に鉄粒子を分散させたもので、磁性エラストマーと呼ばれる。硬さの変化は800倍。世界最高レベルの変化量を示す。磁場をかけると硬くなり、遠ざけると元の硬さに戻る。このような特性を持つ材料は、これまで、水を含むゲルでしか実現できなかった。本研究で初めて、大気中での使用が可能になった。磁場で硬くなるメカニズムを明らかにした。さらに棘皮動物であるナマコの硬さが変わる原理を用いて高効率化を行った。振動実験の結果、弾性率を変えることで振動を制御できることが明らかになった。

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  • 可逆的かつ巨大な弾性率変化を示す磁性ゲルの開発

    研究課題/領域番号:18750184  2006年 - 2007年

    日本学術振興会  科学研究費助成事業 若手研究(B)  若手研究(B)

    三俣 哲

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    配分額:3700000円 ( 直接経費:3700000円 )

    分散性の異なる磁性微粒子を用いて、分散性と巨大磁気弾性効果との相関を検討した。バリウムフェライトは、磁化により10MPaもの弾性率変化を示すが、四三酸化鉄は10kPa程度だった。バリウムフェライト、四三酸化鉄を含むゲルは共に体積分率が0.024以上になると、損失正接の値は大きくなった。これは磁性微粒子のクラスター同士が接触することを示唆している。また、これらのゲルの弾性率は体積分率が0.024以上になると、大きな非線形性を示した。これは磁性微粒子のクラスターが接触することによって生じるPayne効果と考えられる。音速の体積分率依存性から、バリウムフェライト、四三酸化鉄を含むゲルの音速は、それぞれ体積分率0.021、0.018で明確な屈曲点を示すことがわかった。屈曲点がレオロジー測定の結果とほぼ一致したことから、この屈曲点は、微粒子どうしの接触に起因すると考えられる。以上の事実から、磁性微粒子が不均一に分散することが巨大磁気弾性効果の必要条件になることがわかった。磁場のオン・オフにより弾性率が可逆的に変化するゲルが得られた。しかしながら、弾性率の回復に200秒程度を要した。マトリクスのレオロジー特性を制御することにより、回復に時間がかからない材料が得られると期待できる。

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  • さまざまな運動挙動を示す磁性ゲルのアクチュエータへの応用

    研究課題/領域番号:17040007  2005年 - 2006年

    日本学術振興会  科学研究費助成事業 特定領域研究  特定領域研究

    三俣 哲

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    配分額:3900000円 ( 直接経費:3900000円 )

    ドリル状の磁性ゲルを作成した。このゲルは、カラギーナンゲルを鋳型とするアルギン酸ゲルである。アルギン酸ゲルはゲル化が瞬時に起こるため、ゲルの加工はほとんどできなかった。本研究で初めて複雑な形状を有するアルギン酸磁性ゲルが得られた。ポンプを構成する回転子は、螺旋状に加工されている。直径が3mmのとき、毎分300mlで送液することができる。ドリル型に成形された磁性ゲル(直径φ3.8-5.5mm、長さ20-45mm)を用いて送液ポンプを試作した。このポンプは回転磁場により駆動する。非接触で駆動するためチューブの劣化がなく、ポンプ全体が小型化できた。流量はゲルローターの回転数に伴い増加した。最大送液量は5000rpmで28ml/minとなった。回転子の直径が800μm程度になると送液効率が極端に低下することが問題点である。ポリビニルアルコールゲルに四三酸化鉄を分散させたゲルバルブを作成した。グルタルアルデヒドにより化学架橋したゲルである。直径1mmのテフロンチューブを鋳型とした。得られたゲルバルブを直径800μmの流路の脇にセットした。永久磁石をバルブに近づけると、瞬時に流路が塞がれ、送液が止まる。ゲルが磁石に引き寄せられ、物理的に流路を塞ぐ。開閉によるバルブの応答時間は、低水圧(0.3MPa)のときは架橋密度に依存せず、高水圧では架橋密度が高いと2回目以降の応答が悪くなることがわかった。バルブを閉じているとき、架橋密度が高くなると、低水圧で漏れ流量が多くなることがわかった。

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  • 高分子電解質ゲルの粘弾性に及ぼす電荷の効果と電荷間相互作用発現機構の解明

    研究課題/領域番号:15750176  2003年 - 2004年

    日本学術振興会  科学研究費助成事業 若手研究(B)  若手研究(B)

    三俣 哲

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    配分額:3600000円 ( 直接経費:3600000円 )

    高分子電解質ゲルはネットワークにスルホン酸基などの極性基を持ち、架橋点近傍には電荷密度の高いクーロンポテンシャルの井戸が形成されていると考えられている。ゲルを変形させると、電荷密度の高い領域の相対的位置が変位し、大きな静電相互作用が生じると予想される。電解質ゲルの弾性率に関するこれまでの研究では、高膨潤領域における弾性率の増加は網目のストランドの伸張によるものと解釈されてきた。強電解質ゲルである2-アクリルアミド-2-メチルプロパンスルホン酸ナトリウム(PNaAMPS)ゲルの貯蔵弾性率に及ぼす塩の効果を検討し、弾性率とカウンターイオンおよび添加塩によるデバイの遮蔽長との相関について実験的に研究した。
    モノマーに2-アクリルアミド-2-メチルプロパンスルホン酸ナトリウム(NaAMPS)、架橋剤にN,N'-メチレンビスアクリルアミド、開始剤にペルオキソ二硫酸カリウムを用いて50℃、12時間でラジカル重合を行い、ゲルを得た。架橋剤濃度は1〜3mol%である。平衡膨潤に達するまでゲルを純水に浸し、未反応物質を除去した後、10^<-3>M〜10^<-1>MのNaCl水溶液に1週間浸漬させた。動的粘弾性測定装置を用いて、初期ひずみ5〜15%、周波数領域0.1Hz〜100Hz、25℃における複素弾性率を測定した。
    ゲルの貯蔵弾性率はオフセットひずみが大きくなるにつれて増加した。振幅ひずみ〜0.5より小さい領域では、線形粘弾性を示した。一方、弾性率は周波数に殆ど依存せず、典型的な高分子ゲルの周波数応答性を示した。無塩系では、弾性率はE'〜Q^<-1.1>なる膨潤度依存性を示し、ガウス理論よりも膨潤度依存性が大きい。全てのゲルにおいて、塩濃度を高くすると膨潤度は低くなり、弾性率は減少した。高分子電解質ゲル特有の現象である。カウンターイオンおよび塩による遮蔽長を見積もり、遮蔽長とゲルの弾性率との相関を明らかにした。

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  • 高分子ゲルのレオロジー特性と振動吸収材料への応用

    研究課題/領域番号:12740375  2000年 - 2001年

    日本学術振興会  科学研究費助成事業 奨励研究(A)  奨励研究(A)

    三俣 哲

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    配分額:2200000円 ( 直接経費:2200000円 )

    高分子電解質ゲルを用いて貯蔵弾性率の膨潤度依存性について研究した。電解質ゲルは2-アクリルアミド-2-メチルプロパンスルホン酸(AMPS)とN-tert-ブチルアクリルアミド(BAA)をN,N'-メチレンビスアクリルアミド(MBAA)で化学架橋したコポリマーゲルである。AMPSの側鎖にはスルホン酸基があり高分子網目の変形により電荷間での静電反発が予想されるが、BAAゲルには電荷が存在しない。AMPS100%から成るゲルとモル比AMPS:BAA=65:35のコポリマーゲルで貯蔵弾性率の膨潤度依存性を比較した。弾性率と膨潤度にはべき乗則が成り立つが、べき指数はPAMPSゲルで1.00、Poly(AMPS-co-BAA)ゲルは0.75であり、弾性率はPoly(AMPS-co-BAA)ゲルよりPAMPSゲルの方が膨潤度に大きく依存すると考えられる。
    PVA水溶液にバリウムフェライト(BaFe_<12>O_<19>:最大粒径45μm)を加え、グルタルアルデヒドを架橋剤として磁性ゲルを合成した。このゲルを純水中で膨潤させた後、磁場強度1T(テスラ)の磁場中で磁化させ、超音波測定に供した。超音波測定は22.5℃±0.2の恒温水槽中で、10MHzのパルス・バースト波を用いて行った。磁化の前後における縦波弾性率の変化率ΔM'/M'_0をゲルの密度で比較した。磁化方向が音波の進行方向に対して垂直の場合、ゲルの密度が増加するにつれ変化率は大きくなるが、平行の場合はゲルの密度が増加するにつれ減少する傾向を示した。また、貯蔵弾性率を測定した。弾性率の変化は全ての角度においてプラス側に出ている。30度までは変化率に差は見られないが、50度付近から上昇し、90度では約20%の変化が見られた。

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    2017年
    機関名:新潟大学

  • ソフトマテリアル特論

    2015年
    -
    現在
    機関名:新潟大学

  • 化学実験

    2015年
    -
    現在
    機関名:新潟大学

  • 機能材料工学実験IV

    2015年
    -
    2018年
    機関名:新潟大学

  • ソフトマテリアル工学

    2015年
    -
    2018年
    機関名:新潟大学

  • 数理基礎演習(機能材料の数理)

    2015年
    -
    2016年
    機関名:新潟大学

  • 工学リテラシー入門(機能材料工学科)

    2015年
    -
    2016年
    機関名:新潟大学

  • 材料生産システム特定研究Ⅱ

    2015年
    機関名:新潟大学

  • 研究発表演習・発表

    2015年
    機関名:新潟大学

  • 材料生産システム特定研究Ⅰ

    2015年
    機関名:新潟大学

  • 機能材料科学セミナーⅠ

    2015年
    機関名:新潟大学

  • 機能材料科学文献詳読Ⅰ

    2015年
    機関名:新潟大学

  • 機能材料科学演習

    2015年
    機関名:新潟大学

  • 機能材料科学セミナーⅡ

    2015年
    機関名:新潟大学

  • 機能材料科学文献詳読Ⅱ

    2015年
    機関名:新潟大学

  • 高分子材料化学

    2014年
    -
    現在
    機関名:新潟大学

▶ 全件表示