Research On Efficient Transmission Technology Of Point Source In Fluid-like Metamaterials

Using photoacoustic imaging technology to collect cell information has been used to find and diagnose major diseases such as tumor,cardiovascular and cerebrovascular diseases,and brain function.At present,the acquisition of photoacoustic signal in photoacoustic imaging system is mainly far-field imaging.Because of the high frequency of evanescent wave,it can not be transmitted in a long distance.Therefore,based on the current development of negative index metamaterials,a kind of fluid metamaterials structure is designed to realize the negative refraction transmission of evanescent wave in the material and reduce the transmission loss of evanescent wave in the far-field imaging of point source.The research content of this paper mainly includes the following aspects:Firstly,based on the negative index metamaterial design idea,a kind of fluid like metamaterial structure which can suppress the S-wave transmission is constructed,and its acoustic transmission characteristics are analyzed by simulation and amplification experiments.The experimental results show that the structure can effectively suppress the S-wave transmission and has good P-wave transmission effect.Then,the characteristics of P-wave propagation in fluid like metamaterials are studied.Secondly,aiming at the problem that the evanescent wave with high frequency is difficult to transmit in a long distance,a model which can realize point source moving and directional low loss transmission of sound wave is constructed by using the structure design of fluid like metamaterials,including the axisymmetric tubular structure model,the line defect structure model,the artificial period structure model and some special structures model.The corresponding simulation is carried out Real test experiment.The experimental results show that these acoustic transmission models have good characteristics of focusing and directional transmission and can meet the needs of efficient transmission of evanescent wave of point source.Finally,aiming at the problem that the intensity of photoacoustic signal is relatively low in some cases,we constructed a circular and a cylindrical acoustic focusing model.Through simulation verified that these models have good local acoustic field enhancement effect,which can effectively reduce the transmission loss of evanescent wave and realize the acoustic energy concentration.