Multifunctional Acoustic Field Manipulation Based On Artificial Metamaterials

With the development of society and the advancement of science,in order to meet people’s needs for a variety of functional materials,researchers’ horizons have gradually expanded from traditional natural materials to artificial metamaterials.As an important branch,the classical wave system derives the concept of photonic/phononic crystals similar to electronic crystals,thus providing a new means for manual manipulation of wave characteristics.In this paper,we focus on the research of acoustic metamaterials based on three-component unit cells.Using the abnormal acoustic characteristics of negative refraction,total reflection,band gap and interface localized state,we design many artificial acoustic structures including acoustic super-lens,acoustic tubular straight or curved waveguide and acoustic variable/directional transmission channel.The main contents of this paper include:1.Based on the three-element unit cell,the polygonal super-lens structure is designed to realize the artificial negative refraction,which results in high-efficiency acoustic focusing.The intensity of the acoustic pressure at the focus point depends on the frequency of the incident acoustic wave.The closer to the resonance frequency,the higher the acoustic pressure amplitude.In addition,based on the correspondence between frequency and wavelength,the size of the outgoing focus point can also be manipulated by using the artificial polygonal super-lens structure.2.A variety of artificial waveguide structures including tubular straight waveguides,curved waveguides,and barbell waveguides are designed and explored.The interaction between the incident acoustic wave and the structure is used to manipulate the transmission wave-front,thereby reducing the acoustic energy loss during transmission and improving the propagation efficiency of long-distance acoustic wave transport.In addition,the design of the artificial periodic structure effectively suppresses the diffraction effect inside the curved waveguide structure and protects the integrity of the acoustic wave-front.3.The functional structure based on acoustic metamaterials is designed,and a variety of acoustic phenomena including multi-angle directional transmission,multi-path uniform transmission and multi-mechanism directional transmission are realized by taking advantage of the local resonance characteristics of the array structures.The realization of these characteristics of acoustic field manipulation effectively proves the superiority of the design of metamaterial,and provides a new idea for the realization of simple acoustic directional transmission system without complex circuits and instruments.In this paper,the research on the multi-function acoustic field manipulation characteristics based on metamaterial provides a good reference and important theoretical support for the application of high-resolution biomedical imaging,long-distance acoustic energy transport,and multi-angle acoustic directional transmission,as well as a new perspective for the design of new acoustic devices.