A Research On Controlling Sound Field Based On Acoustic Metamaterial And Microparticle Manipulation

Microparticle manipulation techniques such as cell separation,cell arrangement and cell rotation are of great significance in biochemical analysis and early detection of disease.With the development of personalized medicine industry,the portable microfluidic real-time detection technology based on particle manipulation shows great market application potential.Acoustofluidics technology has attracted more and more attention due to its low cost,simple operation and good biological compatibility.It has been applied in various application fields such as whole blood cell separation,exosome separation,muscle tissue culture and biological rapid manufacturing,showing a good application prospect.However,most of the current acoustofluidics technologies are mainly based on the traditional waveguide structure,that is,the sound wave forming standing-wave or traveling-wave exerts acoustic radiation force on the microparticles in the sound field to achieve the purpose of controlling the microparticles.This kind of microparticle manipulation method based on acoustic standing-wave or traveling-wave has a simple structure and can achieve microparticle manipulation in a single mode,but it is difficult to form a complex sound field,so it cannot meet the needs of more detailed and diverse microparticle manipulation.Acoustic metamaterials are periodic composite artificial materials that can well control sound waves.The combination of acoustic metamaterials and acoustofluidics technology will improve the sound field control ability of acoustofluidics chips and enrich the application areas of acoustofluidics chips.Supported by the National Natural Science Foundation of China(Nos.11572121 and 11402083)and the Postgraduate Research and Innovation Project of Hunan Province(No.CX2018B201),this thesis proposes an acoustic metamaterial structure design method based on the two-dimensional point group symmetry theory.This thesis systematically analyses the influence of symmetry on the band gap of acoustic metamaterials and the control of acoustic propagation.The effects of acoustic radiation force and acoustic flow force on particles in acoustic metamaterial structures are studied,and the sound field regulation characteristics of acoustic metamaterials and their applications in the field of microparticle control are studied systematically.The main research work and innovation points of this thesis are as follows:(1)A cross-shaped acoustic metamaterial based on symmetry broken is designed.The internal resonance unit of the metamaterial consists of Helmholtz resonator cavity,and the acoustic transmission direction is adjusted by the eccentric arrangement of the middle square column.The results show that the sound wave always transmits towards the compressed side,which breaks through the general sound transmission phenomenon and achieves the quasi-lossless transmission in the sound network.A kind of hollow hexagonal resonance sound absorber is designed.The results show that the hollow hexagonal resonance sound absorber can effectively prevent the propagation of sound waves in the low-frequency range between monopole resonance and the dipole resonance,providing theoretical guidance for sparse acoustic absorption.The research results provide theoretical guidance for acoustic microfluidic to realize low frequency acoustic wave regulation.(2)The existence of a double Dirac cone in the center of the Brillouin zone of two-dimensional acoustic metamaterials with different symmetry is studied,and the influence of the change of filling rate on the accidental degeneracy of the double Dirac cone is analyzed.The results show that C6vand C6 symmetric acoustic metamaterials can construct double Dirac cones by adjusting the filling rate;while C3v and C3 symmetric acoustic metamaterials cannot construct double Dirac cones by adjusting the filling rate.The existence of a single Dirac cone at the Brillouin zone boundary of a two-dimensional acoustic metamaterial with different symmetries is studied,and the effect of rotation changes on the degeneracy of the single Dirac cone is analyzed.The results show that C6v and C6 symmetric acoustic metamaterials have a robust single Dirac cone and are not sensitive to rotational operation,while the C3v symmetric acoustic metamaterial has an unstable single Dirac cone,which will open or close as the rotation angle changes.Through the analysis of the existence of Dirac cone,it provides theoretical support for the construction of topological phase transition to achieve acoustic topological insulators.(3)C3v symmetric subwavelength acoustic topological insulator is designed,and subwavelength-scale Dirac cone is constructed using Helmholtz resonators.Two different topological interfaces were constructed by the rotation operation,and the topological phase transition and topological edge states were realized.The results show that the acoustic topological insulator has extraordinary transmission characteristics at the topological interface.Based on the band folding theory,a C6v symmetric subwavelength acoustic topological insulator is constructed.By changing the filling rate,a common band gap is constructed to achieve the topological edge state,and the influence of different interfaces on the topological edge state and the efficiency of acoustic wave transmission is analyzed.The results of these studies provide an in-depth analysis of the strength of topological edge states and provide theoretical guidance for the realization of subwavelength acoustic topological insulators.(4)Microparticle manipulation method based on acoustic metamaterial is proposed,which can be used for noncontact particles manipulation.The particle manipulation method based on acoustic metamaterial firstly calculates the band structure,and then calculates the acoustic radiation force under acoustic valley state.Through the force analysis,it is found that the microparticles will be attracted to the acoustic vortex in the air medium by using acoustic metamaterial.It can be extended to water medium,and the rapid separation of microparticles can be achieved through the different bulk modulus.The above research work provides theoretical guidance for the design of new acoustofluidics devices of microparticles manipulation.(5)Microparticle manipulation method based on acoustic topological insulator is proposed,which can be used to separate particles of the same density and size.Double degenerate states are constructed by band folding method,and topological phase inversion and topological interface states are constructed by opening degenerate states through symmetric breaking operation.The acoustic radiation force of different microparticles in the channel is analyzed and compared with the viscous force to determine the microparticle trajectory.The results show that the acoustic topological insulator formed local resonance at the interface and produced acoustic radiation force.Two particles of the same density and size were subjected to different acoustic radiation forces due to different bulk modulus,thus achieving the purpose of microparticle separation.Experiments have been carried out to observe the vibration of air cavity based on acoustic topological insulator.The oscillating water-air surface produces acoustic radiation force and acoustic streaming force,and the orbit rotation control of 20?m microparticle is realized.This work expands the application field of topological insulators and provides new theoretical guidance for designing topological acoustic devices.In this thesis,the structural design of acoustic metamaterials and their application in the field of microparticle manipulation have been studied systematically.To solve the subwavelength wave propagation in acoustic metamaterials,a two-dimensional point group design method is proposed.The effects of symmetry on band structure,transmission characteristics and the presence of Dirac cone are systematically analyzed.The subwavelength-scale topological acoustic metamaterials with different structures such as C3v and C6v are realized.Microparticle manipulation method based on acoustic metamaterial is proposed.The influence of acoustic valley vortex state and the topological interface state on the acoustic radiation force and acoustic streaming force of microparticle is systematically analyzed.The separation of microparticles and rotation of microparticles are realized,which provides theoretical and experimental guidance for the design of a new type of microparticle manipulation acoustofluidics chips.