Numerical calculation of acoustic radiation force and torque on non-spherical particles in Bessel beams

Manipulation of biological cells using acoustic radiation force has drawn a lot of attention in recent years. The force and torque acting on cells are usually estimated from analytical and semi-analytical solutions derived for simple shapes, such as spheres and ellipsoids, typically in an axisymmetric configuration. Since biological cells come in various shapes and sizes and they may have an arbitrary orientation in a microfluidic channel, there is a need for a more versatile and robust numerical model for evaluating the acoustic radiation force and torque. Motivated by this, a three-dimensional boundary element model is developed for calculating radiation force and torque on particles of arbitrary shapes and sizes subjected to arbitrary acoustic waves. The first order acoustic field is solved by using the boundary element method. The second-order, time-averaged tractions are then obtained from the first order field. Subsequently, the resultant radiation force and torque are calculated by integrating the tractions over the surface of a fictitious sphere that en-capsulates the particle. The force and torque on non-spherical particles subjected to acoustic Bessel beams are obtained using this numerical model. The effects of the beam cone angle and particle orientation on the radiation force and torque are investigated.