Pipe inspection robots are being developed for environments that are difficult for humans to enter, such as nuclear power and chemical plants. However, the actuators used for robots are large and heavy, which limits the miniaturization of piping inspection robots. This paper presents an ultra-thin, lightweight film snake-type robot composed of polyimide (PI) film actuators. The proposed robot is expected to enable the easy transport of multiple units. By utilizing the heat and chemical resistance of PI, it can efficiently inspect various targets from multiple locations under harsh conditions. The robot employs a bidirectional bending differential stiffness actuator (BB-DSA). The BB-DSA has two air chambers formed by welding three non-stretchable PI films of different thicknesses. By changing the applied pneumatic pressure between the two air chambers, the actuator achieves bidirectional large bending deformation with a simple structure. A connectable actuator structure is also introduced to reduce the number of pneumatic supply tubes. This contributes to lowering the overall weight of the robot and improving its locomotion performance. The bending angle and generated force of the actuator were evaluated. In addition, a snake-type robot with a reduced number of tubes was fabricated, and its traveling speed and traction force were evaluated. The results show that the maximum traveling speed and traction force were 1.38 mm/s and 14.57 mN, respectively.

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