Friday, October 12, 2012 4:00 p.m. in ETC 4.150
Dr. Likun Zhang
Department of Physics and Center for Nonlinear Dynamics
The University of Texas at Austin
Acoustic beams can exert radiation forces on objects, allowing, for example, manipulation of cells in suspension, assessment of viscoelastic properties of biological tissues, and targeted drug and gene delivery. The force is related to the interaction of the object with the acoustic field because of momentum transport associated with acoustic scattering and energy absorption. Acoustic beams can also carry orbital angular momentum such as the so-called acoustic vortex beams, which are characterized by a screw phase dislocation of the wave field around its propagation axis with a magnitude null at its core. When interacting with an object, the vortex field can transfer the angular momentum to the object, and hence exert torques on the object. The talk will present recent theoretical and experimental advances on negative radiation forces by non-diffracting beams, angular momentum transport of vortex beams, and associated radiation torques on objects. The realization of these beams and their fabrication will allow innovative applications especially for the manipulation of microparticles with acoustic beams of traveling waves, such as the concepts of acoustic tractor beams for pulling the particles or acoustic spanners for noncontact rotational manipulation.