Research On Acoustic Manipulation In Complex Scattering Environments

Acoustic tweezers as an emerging technology in micromanipulation field,has excellent penetrating power and biocompatibility and are considered to be a potential manipulation technology applied in Biomedical field.At present,using acoustic wave to realize the remote location,capture and separation of drug-carrying particles is successful in the case of not considering the complex scattering environment.However,this technique has not been implemented in vivo due to the interference of the scattering environment to the incident wave front.Based on this,this dissertation mainly studies manipulation of the target object using acoustic wave in the complex scattering environment,which will provide a new idea for the acoustic manipulation technology in vivo.Firstly,the theory of acoustic random scattering matrix is studied in this dissertation.When acoustic wave propagates in disordered medium,it will lead to unwanted scattering process,which will seriously destroy the incident wave front required to manipulate the object efficiently.Scattering matrix,as the main observation quantity of scattering process,can accurately describe the relationship between incoming and outgoing waves.The Wigner-Smith operator(also known as Q operator),which is constructed of the scattering matrix,can manipulate the target object in complex scattering environment by determining the incident wave front mode in the far field(the eigenmode of the Q operator).The theoretical results show that the eigenstates of Q corresponding the change of position of the target scatter can transfer the momentum to the object and eigenstates of Q corresponding the change of angle of the target scatter can transfer the angular momentum to the object.Next,computing simulation result verifies the above theoretical results through COMSOL Multiphysics.We study the manipulation of objects in empty waveguides and complex scattering environments respectively.The result demonstrates that injecting the corresponding eigenvector of Q can manipulate objects accurately whether in empty waveguide or complex scattering environment.And injecting the eigenvector with smallest eigenvalue of Q will appear the phenomenon that the sound wave will bypass the object to propagate forward.Finally,the influencing factors of object manipulation in complex scattering environment are explored.It is found that the shape,size,and acoustic parameters(density)of the target object,and the frequency of the incident wave all affect the manipulation effect.The eigenvector of Q can manipulate objects of any shape and size,and the target object with density closer to the density of the surrounding medium and size closer to the wavelength of the incident wave will acquire best manipulation effect.In summary,the acoustic random scattering matrix method can manipulate target surrounded by complex scattering media.This method avoids the iterative complex procedures in other wave front shaping methods and the difficulty of measuring the near-field of objects,which opens up a new direction for acoustic micromanipulation in biophysics.