Flocks of Swimming Micro-robots with Long-range Hydrodynamic Interaction and Objectives

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This project will create flocks of swimming robots that operate in, and cooperatively influence, highly viscous fluid environments. Because of the effect of size on the relative contributions of different fluid forces, micrometer-scale robots in water behave similarly to centimeter-scale robots in viscous fluids such as corn syrup or motor oil. High viscous fluids can also model movement in granular media like sand. One effect of high viscosity is that the movement of one robot may affect other robots many body lengths distant. Thus this project will create new methods of trajectory planning and motion control for large flocks of swimming robots that take these interactions into account. Two selectable modes of control will be the focus of this study. The first is to maximize the long-range effects of the swimming flock, so as to enhance mixing of the fluid environment. The second is to minimize long-range effects, so as to allow stealthy movement of the robot flock. Some potential applications of these flocks include robotic inspection of oil tanks, environmental monitoring and remediation, and multi-agent drug delivery systems in blood vessels. This project is multidisciplinary covering from fundamental fluid mechanics to robot design and control. The research and educational activities associated with this multidisciplinary proposal are expected to make the subject accessible to a broad audience including traditionally under-represented groups and engineering community affiliated with national industries.The creation of artificial swimmers capable of moving and tumbling in highly viscous environments poses numerous fundamental challenges. Swimming in viscous regimes is significantly affected by long-range hydrodynamic interactions that nonlinearly couple the propulsion function of swimmers in a swarm. Long-range hydrodynamic interactions can easily induce chaos, and lead to unpredictable collective behaviors. This project addresses the first three-dimensional controlled flock of swimmers under nonlinear hydrodynamic interactions. As a benchmark, experiments will be conducted using a swimmer called Quadroar, and the capability of this swimmer to switch between (quasi) periodic and chaotic group behaviors will be investigated. Two fundamental missions will be implemented: (i) Active optimal control of a flock to achieve the highest mixing efficiency in the background fluid (Chaotic Mixing mode); and (ii) Active control of a flock such that hydrodynamic interactions cancel each other, that is, swimmers flock with minimally disturbing the surrounding fluid, and remain stealth (Concealed Swarm mode). These modes define new group objectives for environment-mediated robotic swarms.