Aquatic Ionic-Polymer-Metal-Composite Insectile Robot With Multi-DOF Legs

Ionic polymer-metal composite (IPMC) is used in various bioinspired systems, such as fish-and tadpole-like robots swimming in water. The deflection of this smart material results from several external factors, such as water distribution and concentration. IPMC strips with a variety of water concentration on the surfaces and the surface conductivity show various deflection patterns. In this paper, IPMC strips in four initial wetness conditions (100%, 50%, 0% wet on the anode surfaces but 100% wet on the cathode surfaces, and the last one submerged in deionized water) were tested. Even without any external excitation, the strips can bend due to nonuniform water distribution. In order to understand the effects of surface conductivity in an aquatic environment, an IPMC strip with two wires connected to two distinct spots was used to demonstrate the power loss due to the surface resistance. Three types of input signals, sawtooth, sinusoidal, and square waves, were used to compare the difference between the input and output signals measured at the two spots. Thick (1 mm) IPMC strips were fabricated and employed in this study to sustain and drive the robot with sufficient forces. Finally, an aquatic walking robot (102 x 80 x 43 mm, 39 g) with six 2-degree-of-freedom (2-DOF) legs has been designed, implemented, and walked in water at the speed of 0.5 mm/s. The average power consumption is 8 W per leg. Each leg has a thigh and a shank to generate 2-DOF motions. Each set of three legs walked together as a tripod to maintain the stability in operation.