BlueGuppy: Minature maneuverable fish-like robot for investigating collective mechanical intelligence

Fish schools are an excellent example of animal collective behavior. Yet the hydrodynamic interaction among them remains largely unknown. Distinct from low-Re swimmers such as bacteria, schooling fish create persistent fluid vortices that can move downstream agents non-reciprocally. This fluid interaction challenges the use of numerical methods, and experimentalists have traditionally used tethered hydrofoils to provide insights. To increase the number of individuals beyond two, and to investigate dynamic collective behavior such as bait balls, it is essential to design miniature and maneuverable free-swimming robots that can create fish-like fluid disturbances.

In this talk, we present BlueGuppy, a miniature, low-cost, and untethered fish-like robot (9.5 cm, 33.1 g) capable of maneuvering with a single actuator, leveraging nonlinear fluid-structure interactions. BlueGuppy generates net thrust even in the presence of incoming flow. However, its surrounding flow field only replicates that of biological organisms while free-swimming, underscoring the importance of untethered robots for biophysical research. Furthermore, BlueGuppy can achieve maneuverability through tunable kinematics. By varying its flapping frequencies and temporal bias, BlueGuppy accesses a wide range of speeds and turning curvatures. The combination of speed, maneuverability, and simplicity establishes BlueGuppy as a unique platform in the literature with tremendous potential for both uncovering the biomechanics of schooling fish and investigating hydrodynamic interactions among undulatory swimmers in a swarm.