Negative axial radiation force on a fluid and elastic spheres illuminated by a high-order Bessel beam of progressive waves

Abstract

An analytical solution for the scattering of an acoustic Bessel beam of any order by a deformable sphere centered on the beam is used to calculate the acoustic radiation force acting along the wave propagation axis. Situations are noted where, even in the absence of absorption, the radiation force of a high-order Bessel beam acting on the sphere is opposite to the direction of beam propagation. In the present research, the cases of a fluid and solid elastic spheres are considered with particular emphasis on how the mechanical properties and resonances of spheres as well as the beam parameters affect the negative radiation force. Conditions for the negative attracting force on hexane (fluid), aluminum and gold spheres are established, which help in designing acoustic tweezers operating with high-order Bessel beams of progressive waves for potential applications in particle entrapment and manipulation.