Propulsive Efficiency of Robotically Controlled Jellyfish for Ocean Exploration

Propulsive efficiency is a limiting factor for mission duration of ocean monitoring tools. In contrast, Aurelia aurita jellyfish have a propulsive efficiency 97% lower than some underwater vehicles and are adaptable to a wide range of ocean environments. Ocean monitoring tools could potentially capitalize on jellyfish regenerative capabilities and inexpensive electronics by equipping jellyfish with microelectronic swim controllers. One key question is the physiological endurance of jellyfish for long-duration swimming. Here we experimentally investigate swimming durations commensurate with a dive to the deep ocean (e.g. greater than 6000m). While previous work found stimulated jellyfish vertical swimming speeds of up to 4.5 times baseline speeds without swim controllers, propulsive efficiency during free-swimming experiments has not been measured. We utilize a 6-meter tall water tank treadmill to characterize jellyfish swimming endurance and performance experimentally. This apparatus uses computer vision to provide a flow current that opposes the animal and enables continuous swimming without encountering the vertical limits of the tank. Swimming efficiency is inferred from oxygen consumption and measurements of changes in body mass. These experiments inform an analytical model of stimulated jellyfish swimming dynamics and predict performance of jellyfish of different geometries.