A Twistable Ionic Polymer-Metal Composite Artificial Muscle for Marine Applications

Ionic polymer-metal composite (IPMC) artificial muscles (AMs), due to their low driving voltage (<5 V), large strain, soft and flexible structure, and ability to operate in an aqueous environment, are suited for creating artificial fish-like propulsors that can mimic the undulatory, flapping, and complex motions of fish fins. Herein, a newly developed IPMC AM fin with patterned electrodes is introduced for realizing multiple degrees-of-freedom motion, such as bending and twisting. Also, by carefully creating isolated patterns of electrodes on the surface of the polymer-metal composite, sections of the composite can function as an actuator, while other areas can be used for sensing fin deformation and responses to external stimulation. The manufacturing, modeling, and characterization of a twistable AM fin are discussed. The sectored electrode pattern on the AM fin is created using two techniques: masking and surface machining. Using first principles, detailed models are developed to describe the electromechanical transduction for the IPMC AM fin. These models can be used to guide the development of more complex AM fin geometries and electrode patterns. The bending and twisting performance of a prototype twistable AM fin is evaluated and compared to the models. Experimental results demonstrate good twisting response for a prototype fin. Technical design challenges and performance limitations are also discussed.