Robotic Mudskipper for Assessing Efficiency of Hopping on Water

Mudskippers exhibit a unique water-hopping locomotion, landing on water to create a water cavity that may transfer additional energy to subsequent jumps. Studies were conducted with a 65mm long robot to mimic this behavior and determine if energy recapture allows hopping to be a more efficient means of transport. In each recorded trial, the robot starts fully submerged, and motors activate in a three-pulse repeating pattern to create a jump. Parameter optimization was performed with robot fin size, fin placement, and motor activation timing to best replicate hopping. An INA219 current sensor recorded current and voltage, from which power was calculated, while position was tracked from videos using DLTdv8. Power and velocity data were used to find regimes where hopping is more efficient due to energy recapture. The hopping behavior operates at Re ≈ 45,400 and We ≈ 441 based on water-surface impact velocity, with Fr ≈ 0.88 (from impact velocity) to 0.90 (from cycle-averaged velocity), indicating areas where inertial and gravitational forces influence water cavity dynamics. These results show how utilizing water cavity collapse during hopping can reduce total travel energy compared to swimming, offering insights for scalable, energy-efficient amphibious transport and exploration.