Theoretical Simulation And Experimental Research On Micro Particle Manipulation In The Slit Ultrasound Resonance Field

The Acoustic Radiation Force(ARF) is due to acoustic momentum exchange between the acoustic field and particles which are in the acoustic field. The investigation of ARF can be applied to many practical fields because of its no-damage, and contactless particles. The ARF is the foundation of ultrasound drug delivery, acoustic manipulation and so on. These techniques are applied in Biomedical Engineering, Micro Processing Technology and many other important fields. Sound field morphology which can influence the character of the ARF is one of the major factors. Therefore, studying the ARF in various acoustic sound fields could get the optimization parameters of the theory support in medical ultrasound area. There has been considerable progress in the calculations of ARF on various kinds of objects in free ultrasound field. However, the ARF study exerting on the objects in the acoustic complicated field is very few because it is limited to analytic solutions. In this paper, we propose a numerical algorithm combining the FDTD method with momentum-flux tensor to calculate the ARF exerting on particles in ideal fluids. We found that the particle could be subjected to the attraction force because of the Fabry-Perot(FP) effect in the slit acoustic field. What’s more, we set up the experiment platform and observe the experimental phenomena. The detailed study is as follows.Theoretically we first use the two-dimensional finite difference time-domain (FDTD) method to stimulate the transmission spectrum of the slit and the acoustic field. And then combining with the momentum-flux tensor, we study the ARF exerting on a steel cylinder. We found the the steel cylinder can be subjected to the attraction force in the enhanced frequency of the slit. That is FP resonance effect frequency. The direction of the force is towards the ultrasound source and the ARF intensity near the slit is far more than the ARF which is opposite to the ultrasound source in free field. Besides, we also study relationship between the slit width, the slit thickness, the distance from the steel cylinder center to the surface of the slit and the ARF exerting on the steel cylinder.Experimentally we study one steel ball motion feature in the 100KHz acoustic field. The diameter of the steel ball is 1.5mm and the width of the slit is 5mm. The result shows that particle can be subjected to the ARF The motion direction of the particles is far from the ultrasound resource. In the slit acoustic field which is compose of 2mm width of the slit, that is the slit resonant FP sound field, the particles can be subject to attraction force and the motion of the particles is towards the slit.Above all, this thesis studies the ARF exerting on the particles near the slit surface both theoretical simulation and experimental study in the ultrasound field. We found that the surface of the slit can attract the small ball, whose diameter is about lmm, in the slit resonant FP ultrasound field. The results of the study could provide the theoretical support and experimental guidance to the manipulation particles in the slit acoustic field.