Nereus: a metachronal swimming robot for swarm-based sensing in turbulent flows

Metachronal swimmers including shrimp, krill, and copepods are adept at swimming in highly turbulent flow environments—their collective motions have been observed in coastal regions, the open ocean, and underneath sea ice. Their propulsion strategies offer a compelling blueprint for engineering highly maneuverable ocean-exploring robots, enabling effective navigation through some of the most challenging and critically undersampled regions on Earth. In particular, we hypothesize that the coordinated beating of multiple appendages offers unique hydrodynamic benefits for navigating turbulent flows. To test this hypothesis experimentally, we leverage our recently developed Nereus robot, which is propelled by two rows of five appendages each that mimic the morphology of marsh grass shrimp (Palaemon vulgaris). Each of the ten electromagnetically-driven appendages is individually controllable, enabling real-time measurement of hydrodynamic forces and torques at the appendage level. We investigate the hydrodynamics and optimal gaits of metachronal swimming in a variety of unsteady and turbulent flow environments in a water channel. Additionally, we use multiple free-swimming, self-contained robots to investigate the hydrodynamics of metachronal swarming. By enabling coordinated exploration of challenging flow environments, the Nereus network represents a potential paradigm shift in robotic ocean exploration.