Exploring the efficacy of metachronal swimming and pumping at intermediate Reynolds numbers with magnetically actuated artificial cilia*

Flexibility is a key feature of biological structures involved in swimming and flying, enhancing efficiency and performance. Advances in soft robotics enable engineering solutions that can more closely mimic such structures compared to rigid mechanical designs, helping us explore the role of flexibility across a range of biological and hydrodynamic contexts. Here we explore the performance of a coordinated, magnetically actuated array of soft robotic paddles at intermediate Reynolds numbers, modeled after the propulsors of ctenophores (comb jellies). Ctenophores’ paddle-like appendages are arranged in rows and beat sequentially, with a wave travelling opposite to the beating direction (antiplectic metachronal coordination). Our bioinspired propulsors consist of magnetic elastomers, actuated with an external magnetic field. Different frequencies, wave speeds, and phase lags can be encoded in the soft robotic array, allowing us to use particle image velocimetry (PIV) to explore the hydrodynamics of a biologically relevant performance space. We find distinct shifts in momentum flux with phase lag and frequency, showing the versatility of the soft robotic platform to explore the role of flexibility and metachronal coordination across a range of intermediate Reynolds numbers.