RoboNautilus: a cephalopod-inspired soft robotic siphon for underwater propulsion

Abstract

Early nautiloids evolved siphon-like structures hundreds of millions of years ago as a propulsion mechanism for maneuvering in underwater environments. Over time, siphons became the cephalopod method for jetting locomotion, but few bio-mimetic soft robotic replicas have been developed. The principal challenge is the limited selection of solid-state, active soft materials that can replicate the function of the active mantle in a natural siphon. Here, we present a Nautilus-inspired propulsion system that employs multilayered solid-state dielectric elastomer actuators (DEAs) to produce an artificial siphon. The system features a soft robotic siphon, onboard sensors for semi-autnonomous operation, and a 3D-printed shell with an internal air pocket for buoyancy and self-righting ability. Through analytical modeling and empirical approaches, we develop a soft muscle for vortex ring formation and thrust output of 17 mN at 2 kV. These findings provide a framework for designing soft actuators that can be used as new propulsors to enable efficient (Cost of Transport = 2.51), low-noise, underwater locomotion for exploration and environmental monitoring applications.