Underwater Salp-Inspired Soft Structure Contraction with Twisted Coiled Actuators

Underwater compliant-body jet propulsion is among the most efficient of all animal locomotion. Multi-jet propulsion, a less common method of transit used by the Salp, offers a lower cost of transit, higher maneuverability, and redundancy in case of individual failure. Single-jetting robots have been created that are capable of tethered, repeatable swimming and steering. However, these designs were primarily inspired by squid, jellyfish, or other single-jet propulsors. In this work, we instead start with an individual module inspired by a salp chain. We analyze the shape change of different soft bodies activated by artificial muscles. By comparing the effect of body morphology and muscle activation sequence on volumetric change and extrapolated thrust, we can compare our results to those seen by salps. We achieve a maximum volumetric decrease during contraction of 26%.