Soft buckling achieves consistent large-amplitude deformation for pulse jetting underwater robots.

Jellyfish achieve efficient pulse jetting through large-amplitude, low- frequency deformations of a soft bell. This is made possible through large localised deformations at the bell margin. This paper develops a novel soft-robotic underwater pulse jetting method that harnesses the buckling of flexible tubes to generate thrust. Soft material instability is controlled through variation of internal water pressure in the tubes, where we demonstrate repeatable large-amplitude deformations with bell flexion angles of 29 ± 1.5◦ over a frequency range of 0.2 to 1.1 Hz. The actuator is used to propel a soft robotic platform through water, achieving instantaneous velocities of up to 5 cm/s with no noticeable degradation in performance over 1,000 pressure cycles.