I. Introduction
Acoustic vortex (AV) beams have opened a whole new range of applications due to their features associated to rotating wavefronts formed by intertwined helices. Some examples of these are the orbital angular momentum carried, which can be transferred to matter [1]–[7], the capacity to contactless manipulate objects [8]–[13], for high-speed ultrasonic communications [14], subdiffraction and superresolution imaging [15], [16], and more recently, in biomedical applications [17]–[20].