Numerical study of the effect of pressure amplitude and frequency on secondary acoustic radiation force between two polystyrene particles in water

Abstract

Poly(N-isopropylacrylamide) microgels emulate the behavior of natural platelets, promoting wound healing. Our previous studies suggested that ultrasound stimulation of these synthetic platelets further enhances wound healing, by increasing particle displacement and deformation. It is necessary to understand and model the interaction between ultrasound and these particles. We hypothesize that the acoustic radiation force may play a role. Two types of radiation force are considered: a primary radiation force caused by the external acoustic field, and a secondary radiation force resulting from scattering between particles. We present a parametric numerical study of the interaction between polystyrene beads (similar to the synthetic platelets) and an acoustic field, to investigate the effect of magnitude, frequency and bandwidth of excitation field on particle response. This is done via the numerical modeling of the primary and secondary radiation forces using 2-D and 3-D FEM. The 3-D simulations capture the re-scattering effects between the particles. One particle is placed at the origin of the coordinate system (scatterer) and a second particle (probe) is placed in the nodal and anti-nodal pressure planes. The numerical results show a good agreement with the governing theoretical equations proposed by Silva and Bruus, suggesting the relevance of the radiation force hypothesis.