Design, Modeling and Testing of a Flagelluminspired Soft Underwater Propeller Exploiting Passive Elasticity Flagellated microorganism are regarded as excellent swimmers within their size scales. This, along with the simplicity of their actuation and the richness of their dynamics makes them a valuable source of inspiration to design continuum, selfpropelled underwater robots. Here we introduce a soft, flagelluminspired system which exploits the compliance of its own body to passively attain a range of geometrical configurations from the interaction with the surrounding fluid. The spontaneous formation of stable helical waves along the length of the flagellum is responsible for the generation of positive net thrust. We investigate the relationship between actuation frequency and material elasticity in determining the steadystate configuration of the system and its thrust output. This is ultimately used to perform a parameter identification procedure of an elastodynamic model aimed at investigating the scaling laws in the propulsion of flagellated robots.

Design and Characterization of a Fully Autonomous Underactuated Soft Batoidlike Robot Batoids use their large pectoral fins to achieve unique maneuverability and propulsive performance. In this work, the design, fabrication and characterization a soft batoidlike robot is presented. The robot is designed to mimic undulatory rajiform locomotion. The design is underactuated, simple and robust and well suited for propulsive performance experiments thanks to its full autonomy, long battery life, and wireless recharging capabilities. The robot has a 180mm body length, a maximum flapping amplitude of 60deg, and reaches a peak speed of 0.93 body length per second. In order to characterize its swimming kinematics and propulsive forces a special setup was built using an instrumented holder and high speed video. Experiments were conducted to characterize propulsive force generation with varying fin flapping frequencies (from 1hz to 2. 4hz), amplitudes, and wavelengths. The results show that while both flapping frequency and amplitude influence propulsive forces, for the locomotion modes tested, flapping frequency has a stronger effect on both thrust and side forces. Furthermore, larger side forces than thrust forces are produced for the same swimming parameters.