Acoustic Manipulation Of Particles By Acoustic Artificial Structures

In recent years,acoustic manipulation has attracted much attention.Acoustic manipulation is a contactless,tunable and biocompatible tool for cell separation,food delivery and micro-fabrication.It is closely related to acoustic radiation force(ARF).The interaction of the incident field with particles,manifested as an exchange of momentum,can exert ARF on particles such as pushing or pulling particles.Among acoustic manipulation,it is feasible to adjust the sound field from two aspects of the sound source and the sound.From the aspect of the sound source,the conventional system with standing wave or Gaussian beams which is usually generated directly by the transducer,which is difficult to redesign efficiently.However,from the aspect of sound propagation,acoustic artificial structures,such as sonic crystals(SCs),can modulate acoustic waves or elastic waves,which provides the possibility for sound field optimization.So this provides a new platform for acoustic manipulation.Researchers have begun to use acoustic artificial structure to optimize the sound field,which can be used for particle manipulation.On the basis of previous studies,this paper is devoted to making use of acoustic artificial structure to adjust the acoustic radiation force.The finite element method(FEM)combined with momentum-flux tensor is used to obtain the acoustic radiation forces exerted on the particles.And the finite element software is used to conduct numerical simulation.The main works of this paper are as follows:Firstly,in the second chapter,we use the one-dimensional(1D)acoustic grating to manipulate acoustic waves,which can be used for acoustic trapping and alignment.We theoretically and experimentally prove that this 1D grating can realize particles manipulation in air.The numerical results show that the 1D grating can modulate the sound field and according to the distribution of acoustic waves,this system can make trapping and alignment come true.Secondly,in the third chapter,we report particle trapping and transport by 1D phononic plate with oblique grating structure.The numerical results show that there is more than one resonance peak in the oblique grating structure.At the resonances,the negative ARFs exerted on the particles result from the anti-symmetric vortex velocity field near the oblique grating structure.And the corresponding acoustic trapping positions of different resonances are also different,which provides the possibility for particle transport by changing resonant frequencies.In a word,we theoretically make particle trapping and transport in oblique grating structure come true.Finally,in the fourth chapter,based on the broadband acoustic manipulation system,we theoretically realize selective particles manipulation in space by introducing quasi-periodic structures.The results show that different period assembly have its own resonant frequency.And we can selectively manipulate sound field in space by changing frequencies,which can realize the spatial selective manipulation of particles.