Three-dimensional Acoustic Radiation Force on an Arbitrary Located Elastic Sphere

Diego Baresch , Jean-Louis Thomas (1) , Régis Marchiano

1 INSP - Institut des Nanosciences de Paris

This work aims to model the forces acting on an elastic sphere placed in the field of an acoustic vortex. From this theoretical investigation we derive an expression of the axial and transverse forces exerted on the sphere. Acoustic vortex refers to a type of beam having an helicoidal wave front. Such a wavefront is due to a screw type phase singularity and hence the beam has a central dark core of zero amplitude surrounded by a high intensity ring. The spheres are allowed to be arbitrarily located in the acoustic field, thus, one can study the axial and transverse stability of the spheres. We find that an azimuthal force component appears and is capable to rotate the sphere around the propagation axis. This confirms the transfer of orbital angular momentum from the beam to the sphere. Furthermore, axial forces may turn negative when appropriate parameters are selected and yields a dragging force towards the source of the beam acting as a Tractor Beam. In addition to extending the understanding of the nature of forces arising in an acoustic vortex, numerical results provide an impetus for further designing acoustic tweezers for potential applications in particle entrapment and remote controlled manipulation.

Mots clés: Radiaton force; Acoustic Vortex; scattering

Domaines: Acoustique [physics.class-ph]

Diego Baresch, Jean-Louis Thomas, Régis Marchiano. Three-dimensional Acoustic Radiation Force on an Arbitrary Located Elastic Sphere. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00810890⟩