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Monolithic IPMC Fins for Propulsion and Maneuvering in Bioinspired Underwater Robotics

Joel J. Hubbard, Maxwell Fleming, Viljar Palmre, David Pugal, Kwang J. Kim, and Kam K. Leang*

ABSTRACT: Emerging bioinspired underwater systems, such as autonomous ocean mapping and surveillance vehicles, that maneuver through their environment by mimicking the swimming motion of aquatic animals, can benefit from soft monolithic actuators and control surfaces capable of undergoing complex deformations. Herein, an electrically driven ionic polymer–metal composite (IPMC) artificial muscle with uniquely patterned electrodes for creating complex deformations is presented. The surface electrode pattern on the IPMC is created using a simple surface machining process. By selectively activating specific regions of the IPMC, bending, twisting, flapping, and other bioinspired locomotive behavior can be achieved. For instance, the bending and twisting response of an example 50 mm by 25 mm by 0.5 mm patterned IPMC actuator is characterized to determine its range of motion, output force and torque, as well as its effectiveness as a fish-fin-like propulsor. The experimental results show that the twisting angle exceeds 8 ; the blocking tip force and torque can be as high as 16.5 mN (at 3 V) and 0.83 N mm (at 4 V), respectively (driven at 0.05 Hz); and an average thrust force of approximately 0.4 mN (driven by 4-V sinusoidal input at 1 Hz) can be generated. These newly developed IPMC fins can be exploited to create novel and efficient propulsors for next-generation underwater robotic vehicles. An example bioinspired robotic fish is presented which exploits the capabilities of the patterned IPMCs for propulsion and maneuvering, where an average maximum swimming speed of approximately 28 mm/s is reported.