Bio-inspired robotic manta ray powered by ionic polymer–metal composite artificial muscles

The manta ray (Manta birostris) is the largest species of rays that demonstrates excellent swimming capabilities via large-amplitude flapping of its pectoral fins. In this article, we present a bio-inspired robotic manta ray using ionic polymer–metal composite (IPMC) as artificial muscles to mimic the swimming behavior of the manta ray. The robot utilizes two artificial pectoral fins to generate undulatory flapping motions, which produce thrust for the robot. Each pectoral fin consists of an IPMC muscle in the leading edge and a passive polydimethylsiloxane membrane in the trailing edge. When the IPMC is actuated, the passive polydimethylsiloxane membrane follows the bending of the leading edge with a phase delay, which leads to an undulatory flapping motion on the fin. Characterization of the pectoral fin has shown that the fin can generate flapping motions with up to 100% tip deflection and 40° twist angle. To test the free-swimming performance of the robot, a light and compact on-board control unit with a lithium ion polymer battery has been developed. The experimental results have shown that the robot can swim at 0.067 BL/s with portable power consumption of under 2.5 W.