Propagation of acoustic waves and determined radiation effects on axisymmetric objects in heterogeneous medium with irregular interfaces

Acoustic tweezers have shown great potential in revolutionizing fields such as noninvasive surgery and drug delivery. However, the current theoretical prediction and quantitative analysis of acoustic radiation force and torque are limited by the assumption of a homogeneous medium and spherical micro-objects. In this study, a theoretical model to address this limitation is proposed by considering the propagation of acoustic waves in layered heterogeneous media with irregular interfaces. The approach begins by constructing a propagation model based on plane wave decomposition and scalar diffraction theory to describe the behavior of acoustic waves passing through irregular interfaces. The spatial distribution of the acoustic field after passing through these interfaces is then determined using the angular spectrum method. To account for the geometric characteristics of axisymmetric objects, a conformal transformation approach is incorporated, allowing us to efficiently establish a theoretical model for the acoustic radiation force and torque exerted on these objects suspended in the layered medium. To validate the model, the computed acoustic pressure fields and radiation forces are compared with results obtained from full three-dimensional numerical simulations. The agreement between the two sets of results demonstrates the effectiveness of the proposed method. This theoretical model is expected to contribute significantly to the development of acoustic tweezers technology, enabling the manipulation of irregular micro-objects in multi-layer medium and providing important theoretical support for the application of acoustic tweezers in complex medium.