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In late years many kinds of home-use robot have been developed to assist elderly care and housework. Most of these
robots are designed with conventional electromagnetic motors. For safety it is desirable to replace these electromagnetic
motors with artificial muscle. However, an actuator for such a robot is required to have simple structure, low driving
voltage, high stress generation, high durability, and operability in the air. No polymer actuator satisfying all these
requirements has been realized yet. To meet these we took following two approaches focusing on conducting polymer
actuators which can output high power in the air.
(Approach 1) We have newly developed an actuator by multiply laminating ionic liquid infiltrated separators and
polypyrrole films. Compared with conventional actuator that is driven in a bath of ionic liquid, the new actuator can
greatly increase generated stress since the total sectional area is tremendously small. In our experiment, the new actuator
consists of minimum unit with thickness of 128um and has work/weight ratio of 0.92J/kg by laminating 9 units in 0.5Hz
driving condition. In addition, the driving experiment has shown a stable driving characteristic even for 10,000 cycles
durability test. Furthermore, from our design consideration, it has been found that the work/weight ratio can be improved
up to 8J/kg (1/8 of mammalian muscle of 64J/kg) in 0.1Hz by reducing the thickness of each unit to 30um.
(Approach 2) In order to realize a simplified actuator structure in the air without sealing, we propose the use of ionic
liquid gel. The actuation characteristic of suggested multilayered actuator using ionic liquid gel is simulated by
computer. The result shows that performance degradation due to the use of ionic liquid gel is negligible small when ionic
liquid gel with the elasticity of 3kPa or less is used.
From above two results it is concluded that the proposed multilayerd actuator is promising for the future robotic
applications because it has advantages of high work/weight ratio and in-the-air operation, in addition to advantages of
conventional polymer actuators.
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