Vol.9 No.3 2017

Research paper : Development of human-friendly polymeric actuators based on nano-carbon electrodes (Kinji Asaka)−121−Synthesiology - English edition Vol.9 No.3 (2017) 6.3 Comparison of the performances of a bucky gel actuator and a piezoelectric ceramics actuatorThe bimorph-type actuator made of piezoelectric ceramics is known as the commercially available actuator that undergoes voltage-driven bending deformity. Here, we shall compare the actual values for a piezoelectric ceramics actuator and a bucky gel actuator (Table 1).For workability, compared to piezoelectric ceramics that requires complex processes such as sintering and polling, the bucky gel can be mass produced by printing and other methods, and it is clear it has excellent workability. Looking at the actuator property, the bucky gel is low-voltage driven and has large deformation, while the piezoelectric ceramics excels in high response rate and large generative power. The bucky gel actuator can be used for products that require low-voltage-drive and large deformation that cannot be handled by piezoelectric ceramic actuators. We believe the issue of low generative power can be overcome in the future by developing the stacking technologies taking advantage of bucky gel’s workability.7 Application of the bucky gel actuator to light and thin braille displaysWe worked on several applications in thin and light devices. Here, we shall describe the braille display development that reached the stages of prototype development and user evaluation.The braille system where the letters are represented by six dots is the only writing system that can be used by the visually impaired. Currently, there are about 300 thousand visually impaired people in Japan, and there are 30 thousand braille users. Due to the advancement of digital information technology in recent years, braille displays have become commercially available as information terminals for the visually impaired. These use the piezoelectric system or solenoid actuators, and in principle, the size of the element becomes large. Therefore, such information terminal devices cannot be carried around conveniently. Moreover, only one line can be displayed. The users have requested for a device that is portable and can display multiple lines that allows easy reading.Against the above background, under the FY 2009 R&D Project for Service and Support for Persons with Disabilities[12] and FY 2010 R&D Project for Service and Support for Persons with Disabilities[13] of the Ministry of Health, Labour and Welfare, we engaged in joint research for applying the bucky gel polymeric actuator to light and thin braille displays with the following organizations: the Sendai R&D Center, Alps Electric Co., Ltd.; Research and Education Center for Natural Sciences, Keio University; and School of Engineering, the University of Tokyo. If the braille can be presented by arranging the actuator filmstrips in planar configuration and by controlling each element independently with electric signals, it is possible to create a light and thin multi-line braille display. We continued the prototype development for braille displays and created a demo prototype for an ultra-thin light braille display that can display six letters (Fig. 6).Through evaluation experiments by users using this demo prototype, high expectations were raised for various uses of such thin and light multi-line braille displays. For example, it may be used to replace the liquid display control panels of various home appliances and bank ATMs, or used for page displays through multi-line display. There are also expectations for displaying figures and tables. We also received inquiries from overseas such as Europe and Canada as well as throughout Japan.In the evaluation experiment, several problems such as durability and reliability of the device as well as uctuation in properties became apparent. We continued improvement of the actuator and the mechanical structure of the braille display, and saw a clear way for realizing thin and light braille display.Schematic diagram of the braille pin movement3 gf100 gf1s1 ms1 mm2 µm100 V or more3 V or less○×Bucky gelPiezoelectric ceramicsGenerating forceResponseDisplacementDriving voltageWorkabilityActuatorNote: The performance values are representative values of a 5 mm × 5 mm size actuator. The values for a piezoelectric ceramic actuator are literature values of the bimorph type.Fig. 6 Braille display using the bucky gel actuatorTable 1. Comparison of the performances of bucky gel and piezoelectric ceramics actuators

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