Small fish robots, the size of a killifish – 5 cm long – are potentially in finding disaster victims in flooded areas, because of their ability to navigate narrow confines. Powering such robots, however, becomes a question, since the easiest answer – rechargeable batteries – has low energy density. The “Power Tube” we developed is a small and ultra-light passive-type polymer electrolyte fuel cell. Based on this fuel cell technology, we fabricated a 110 mm fish robot combining a drive, consisting of a DC motor and link, with a Power Tube having a hydrogen generator. We also fabricated an energy-efficient submersible fish robot with neodymium magnets and coil actuators, that methanol-fueled Power Tubes powered with a voltage booster.

-The swimming velocity of fish robots are extremely low in comparison with actual live fishes. To investigate the superior propulsive efficiency of actual fish and find measures to improve the propulsive performance of fish robots, a flexible fish robot was developed. The effects of the flexibility of tail fin on the propulsive force were investigated by using the fish robot and three-dimensional CFD. Consequently, the flexibility of tail fin is very important for fish robots to swim efficiently, because the vortex rings generated from a flexible tail fin is useful to maintain reverse Karman vortices for a long time.

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