Numerical simulation of particle motion in a phase modulated surface acoustic wave microfluidic device

Contactless sorting of particles and cells in microfluidic devices is beneficial for various industrial and scientific applications. Among such techniques, acoustic sorting methods are favored for their reconfigurability and label-free processing capabilities. A phase modulated sorting method is proposed in this article as an alternative to time-of-flight sorters. The method has been analyzed theoretically and experimentally validated by considering the primary acoustic radiation and viscous drag forces. However, in real devices, acoustic streaming that arises from the damping of acoustic waves within the fluid cavity can adversely affect sorting. This paper presents therefore a numerical study of the influences that the primary radiation force and acoustic streaming can have on the phase modulated sorting method. The article highlights the existence of a critical particle size, above which acoustic streaming effects governing the behavior of small size particles are dominated by the primary radiation force. The model is extended for trajectory simulation in phase-modulated fields and validated with experimental data.