Acoustical hooks: A new subwavelength self-bending beam

In this work, we report the first experimental observation of a new type of near-field curved acoustic beam confirmed by simulations. This new curved acoustical beam is generated by asymmetric distribution of the vortices in a polymer Janus particle (particle with broken symmetry) immersed in water. The origin of the vortices is in the conversion of an incident longitudinal wave mode to a shear wave in a solid and then back to a longitudinal wave in the water and has unique features, the radius of curvature of acoustical hook is less than the wavelength. Indeed, it is the smallest radius of curvature ever recorded for any acoustical beams. These results may be potentially useful when an object, located in the path of the beam, must be avoided. It could also have potential applications in particle manipulations.