Topological water-wave structures manipulating particles

Abstract

Topological wave structures, such as vortices and skyrmions, appear in a variety of quantum and classical wave fields, including optics and acoustics. In particular, optical vortices have found numerous applications ranging from quantum information to astrophysics. Furthermore, both optical and acoustic structured waves are crucial for manipulation of small particles, from atoms to macroscopic biological objects. Here we report on the controllable generation of topological structures -- wave vortices, skyrmions, and polarization M\"{o}bius strips -- in interfering gravity water waves. Most importantly, we demonstrate efficient manipulation of subwavelength and wavelength-order floating particles with topologically structured water waves. This includes trapping of the particles in the high-intensity field zones, as well as controllable orbital and spinning motions due to the orbital and spin angular momenta of water waves. Our results reveal the water-wave counterpart of optical and acoustic manipulations, which paves the avenue for applications in hydrodynamics and microfluidics.