Manipulation of microparticles at liquid–gas interfaces is a desired tool in many applications including self-assembly into patterns and structures. Recent advances in confinement and manipulation of micro-particles and ultracold atoms using optical waves inspired new ideas related to the control of particles at liquid–gas interfaces using the vortex lattice made of dynamic periodic patterns on the liquid surface driven by crossed-surface wave.

We show that spinners at the liquid–gas interface can be efficiently manipulated using the surface-wave analogue of optical lattices. We demonstrate that by placing active magnetic spinners inside such the vortex lattice, one makes a powerful tool, which allows manipulation, and self-assembly of spinners, turning them into vehicles capable of transporting matter and information between autonomous vortex lattice unit cells. By changing the spinning frequency or the wave amplitude, one can precisely control the spinner orbit. Multiple spinners within a unit cell self-organize into dynamic clusters, e.g., triangles or squares, orbiting around the centre of the cell.

We also report self-guided propulsion of fast-spinning particles on a liquid surface in the presence of a solid boundary. Above some critical spinning frequency, corresponding to higher rotational Reynolds numbers, such particles generate localized 3D vortices and form composite ‘spinner-vortex’ quasi-particles with nontrivial, yet robust dynamics. Namely, such spinner vortices are attracted and dynamically trapped near the boundaries, propagating along the wall of any shape as ‘liquid wheels’.

The results offer novel confinement methods of surface particles and open ways to engineer surface vehicles.

Zoom meeting: https://anu.zoom.us/j/95739287775

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