Study On Acoustic Radiation Force Of Free Particles In A Viscous Liquid And Biological Tissue

Acoustic radiation force(ARF)is a non-linear effect of sound field and arises from the momentum transfer between the sound field and the object.With the development of science and technology,the non-contact manipulation of tiny particles is becoming more and more important.Compared with other forces suitable for particle manipulation,the ARF has the advantages of high biocompatibility,non-invasive,no label operation,wide range of particle types and large scale span.These advantages make the manipulation using ARF have a wide application prospects in the fields of biophysics and ultrasound medicine and become one of the research hotspots in the field of acoustics.With the progress of science and technology,the control technology using ARF has made considerable development,but there are still some theoretical gaps in theory and quantitative measurement.If the gaps could be solved,so as to conduct a more in-depth comprehensive study of the ARF,the application of ARF in many fields could be realized,and the miniaturization,integration,intellectualization of its components and equipment also could be achieved better.In this dissertation,ARFs acting on a free cylindrical or spherical particle of different materials in viscous fluids and biological tissues are studied.The dissertation is divided into following sections:In chapter I,the research connotation,characteristics and research category of ARF are briefly introduced.The research status at home and abroad and the main content of this research work are summarized.In chapter II,the scattering theory of sound field is introduced,and the scattering coefficients of a free cylindrical or spherical particle in viscous fluid are deduced,which lays a foundation for further study of the related ARF.In chapter III,the ARF of a free cylindrical particle in a bounded viscous fluid is deduced and given.The effects of the fluid viscosity,particle distance from boundary,particle material and plane wave incident angle on the ARF are analyzed by numerical simulation.Trajectories of the cylinder are analyzed based on Newton's second law of motion and Runge-Kutta method.The results show that the magnitude and direction of the ARF depend on the selection of various factors,so the motion of particles can be controlled and adjusted by selecting appropriate parameters to achieve more efficient particle control.Finally,the finite element simulation(FEM)is used to verify the correctness and effectiveness of the theoretical results in this chapter.In chapter IV,the ARF of a free spherical particle in a viscous fluid when plane wave incident is derived.The corresponding experiments are designed.Taking the spherical polystyrene particle as an example,the ARFs of the spherical polystyrene particles are measured experimentally and compared with the theoretical results.The results show that the variations of ARFs of the spherical particle obtained by theoretical prediction and experimental measurement are in good agreement.In chapter V,based on the image of an abdominal tissue wall tissue,the sound field of ultrasonic propagating in the abdominal wall tissue is simulated using k-Wave,and the sound field distribution is obtained.And then the distribution of ARF in the tissue is also presented.Moreover,the effects of the width,spacing,number of elements and working frequency on the ARF are calculated and analyzed.Results show that these parameters can be selected and adjusted according to actual needs in ARF elastography,which makes the elastography technology more accurate and efficient.This study lays a basis for the application of ARF in elastography technology,and will guide the later improvement of the technology.The last chapter undergoes summary and discussion of the whole text,summarizes the main innovations of this dissertation,and gives some prospections of future work that may have academic and application value.All in all,in this dissertation,the free states of a target and the wide viscosity of the fluid in the practical applications of particle manipulation are considered.The expression of ARF on a free cylinder in a bounded viscous fluid is derived.The ARF of a free spherical particle in a viscous fluid is analyzed theoretically and experimentally.Through numerical calculation,the physical phenomena and mechanism of ARF acting on a free cylindrical or spherical particle in a viscous fluid and biological tissue are further revealed,which is helpful to better understand the potential mechanism of ARF manipulation,and provides a basis for the optimization design and technical improvement of the equipment.The study of this dissertation makes the theoretical study of the ARF further to the practical application environment,and it also has a guiding and reference role for the theoretical and experimental research in related fields.