A review of studies on the motion of particles under the influence of acoustic waves in microfluidic systems

The use of acoustic waves to control and manipulate suspended particles in the fluid has attracted particular attention in the last two decades. The propagation of acoustic waves in the fluid medium may affect the suspended particles mainly by two factors. The initial effect of wave propagation directly acts on the particles and causes the application of force on them via fluid medium. In viscous fluid, due to the wave attenuation and the formation of velocity gradients due to viscosity, secondary fluid streaming form that can indirectly affect the particles. Due to the wide applications of this technology in medical and biological fields and the complexity of the experimental work in micrometer dimensions, there is a growing demand for analytic studies and theoretical insights on this subject. The subject of the present paper is a review on the analytical studies of the mechanisms affecting the movement of particles under the influence of acoustic waves propagating in the microfluidic systems. This review article presents a historical review of the early theories for the calculations of acoustic radiation forces and also the progress of these theories up to the now. Also, a review of the existing research results, problems and limitations, and the effect of different parameters on estimating these results is presented.