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A 4 V Operation, Flexible Braille Display Using Organic Transistors, Carbon Nanotube Actuators, and Organic Static Random-Access Memory

Authors

  • Kenjiro Fukuda,

    1. Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
    Current affiliation:
    1. Research Center for Organic Electronics, Yamagata University, 4-3-16, Jonan, Yonezawa, Yamagata, 992-8510, Japan
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  • Tsuyoshi Sekitani,

    1. Department of Electrical and Electronic Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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  • Ute Zschieschang,

    1. Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
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  • Hagen Klauk,

    1. Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
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  • Kazunori Kuribara,

    1. Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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  • Tomoyuki Yokota,

    1. Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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  • Takushi Sugino,

    1. Research Institute for Cell Engineering, National Institute of Advanced Industrial Science and Technology (AIST), Midorigaoka 1-8-31, Ikeda, Osaka 563-8577, Japan
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  • Kinji Asaka,

    1. Research Institute for Cell Engineering, National Institute of Advanced Industrial Science and Technology (AIST), Midorigaoka 1-8-31, Ikeda, Osaka 563-8577, Japan
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  • Masaaki Ikeda,

    1. Functional Chemicals R&D Laboratories, Nippon Kayaku Co., Ltd. 3-26-8, Shimo, Kita-ku, Tokyo, 115-8588, Japan
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  • Hirokazu Kuwabara,

    1. Functional Chemicals R&D Laboratories, Nippon Kayaku Co., Ltd. 3-26-8, Shimo, Kita-ku, Tokyo, 115-8588, Japan
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  • Tatsuya Yamamoto,

    1. Department of Applied Chemistry, Hiroshima University, 1-4-1, Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8527, Japan
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  • Kazuo Takimiya,

    1. Department of Applied Chemistry, Hiroshima University, 1-4-1, Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8527, Japan
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  • Takanori Fukushima,

    1. Functional Soft Matter Engineering Laboratory, Advanced Science Institute, RIKEN, 2-1 Hirosawa,Wako, Saitama, 351-0198, Japan
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  • Takuzo Aida,

    1. Department of Chemistry and Biotechnology, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
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  • Makoto Takamiya,

    1. VLSI Design & Education Center, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo, 153-8505, Japan
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  • Takayasu Sakurai,

    1. Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
    2. Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo, 153-8505, Japan
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  • Takao Someya

    Corresponding author
    1. Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
    2. Department of Electrical and Electronic Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
    3. Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo, 153-8505, Japan
    4. Core Research for Evolutional Science and Technology, Sanban-cho Bldg, 4F, 5, Sanban-cho, Chiyoda-ku, Tokyo, 102-0075, Japan
    • Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
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Abstract

A sheet-type Braille display operating at 4 V has been successfully fabricated by integrating organic an static random-access memory (SRAM) array with carbon nanotube (CNT)-based actuators that are driven by organic thin-film transistors (control-TFTs). The on current of organic control-TFTs that drive CNT actuators exceeds 3 mA, the mobility exceeds 1 cm2 V−1s−1, and the on/off ratio exceeds 105 at an operational voltage of 3 V. By adjusting the process time for the formation of the aluminum oxide dielectrics, the threshold voltage of the organic TFTs can be systematically controlled. This technique leads to an improved static noise margin of the SRAM and enables its stable operation with a short programming time of 2 ms at a programming voltage of 2 V. As a demonstration of the operation of one actuator with one control-TFT and SRAM: the displacement of actuator exceeds 300 μm at an operation voltage of 4 V, which is large enough for a blind person to recognize the pop-up of braille dots. Integrating the SRAM array reduces the frame rate of a 12 dot × 12 dot display from 1/21.6 s to 1/2.9 s.

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