Artificial Soft Cilia with Asymmetric Beating Patterns for Biomimetic Low‐Reynolds‐Number Fluid Propulsion

TLDR

Low‑Reynolds‑number fluid propulsion is often achieved by arrays of cilia that use spatial asymmetry between effective and recovery strokes, but replicating this asymmetry artificially is challenging. The authors develop an artificial soft cilium composed of two independently controllable pneumatic actuators. The two degrees of freedom enable precise adjustment and investigation of spatial asymmetry in the cilium’s beating pattern. Measurements confirm that spatial asymmetry produces fluid propulsion, providing a platform to study ciliary transport mechanisms and emulate biological viscous propulsion.

Abstract

Abstract In nature, liquid propulsion in low‐Reynolds‐number regimes is often achieved by arrays of beating cilia with various forms of motion asymmetry. In particular, spatial asymmetry, where the cilia follow a different trajectory in their effective and recovery strokes, is an efficient way of generating flow in low Reynolds regimes. However, this type of asymmetry is difficult to mimic and control artificially. In this paper, an artificial soft cilium that comprises two pneumatic actuators that can be controlled individually is developed. These two independent degrees of freedom allow for the first time adjustment and study of spatial asymmetry in the cilium's beating pattern. Using low‐Reynolds‐number flow measurements, it is confirmed that spatial asymmetry allows for the generation of fluid propulsion. These two‐degree‐of‐freedom soft cilia provide a platform to study ciliary fluid transport mechanisms and to mimic biologic viscous propulsion.