Bidirectional Wave-Propelled Capillary Spinners

TL;DR

This study demonstrates how chiral objects on a vibrating fluid interface can be remotely controlled to rotate and steer, revealing new wave-mediated propulsion mechanisms with potential applications in active matter systems.

Contribution

The paper introduces a novel wave-powered propulsion method for chiral floating objects, enabling controlled rotation and steering through modulation of driving parameters.

Findings

Chiral objects exhibit steady, reversible rotation controlled by geometry and driving frequency.

Scaling laws and models explain the physical mechanism behind the rotation.

Remote steering of asymmetric, chiral bodies along 2D trajectories is achieved by tuning the driving frequency.

Abstract

When a solid body floats at the interface of a vibrating liquid bath, the relative motion between the object and interface generates outwardly propagating surface waves. It has recently been demonstrated that millimetric objects with fore-aft mass asymmetry generate an associated asymmetric wavefield and consequently self-propel in unidirectional motion. Harnessing this wave-powered mechanism of propulsion, we here demonstrate that chiral objects placed on a vibrating fluid interface are set into steady, yet reversible, rotation, with the angular speed and direction of rotation controlled by the interplay between object geometry and driving parameters. Scaling laws and a simplified model of the wavefield reveal the underlying physical mechanism of rotation, while collapsing experimental measurements of the angular velocity across parameters. Leveraging the control over the chiral object's direction of rotation, we then demonstrate that a floating body with an asymmetric mass distribution and chirality can be remotely steered along two-dimensional trajectories via modulation of the driving frequency alone. This accessible and tunable macroscopic system serves as a potential platform for future explorations of chiral active and driven matter, and demonstrates a mechanism by which wave-mediated fluid forces can be manipulated for directed propulsion.