Design And Study Of Carbon Nanotube Thin Film Thermoacoustic Transducer Array

Carbon nanotube(CNT)film is novel thermoacoustic material.It can generate acoustic wave based on the principle of thermoacoustic effect with stable sound pressure response in a wide frequency range.Totally different from the traditional transducer,CNT thin film generates sound without mechanical vibration.Hence,no complex matching layer is needed and crosstalk caused by electromechanical interaction is avoided.Moreover,CNT thin film has the advantages of excellent flexibility,easy tailoring,good self-supporting performance and low cost.Hence,it is found that CNT thin film is very promising for fabricating novel thermoacoustic transducer array,to effectively solve the problems of narrow bandwidth,complex structure,difficult fabrication,crosstalk and heavy pollution faced by the traditional piezoelectric transducer array.Furthermore,CNT thin film thermoacoustic transducer array is expected to provide a new idea for the simplification and miniaturization of acoustic equipment,to reduce the economic and time cost and promote the development of the equipment used in medical,nondestructive testing and sonar.In this paper,taking full advantage of the excellent thermoacoustic and mechanical properties of CNT thin film,three types of CNT thin film thermoacoustic transducer array are proposed,i.e.CNT thin film square-matrix transducer array,CNT thin film annular transducer array and CNT thin film spherical transducer array.Firstly,considering the influence of specific heat capacity per unit area and heat flux,the model of thermoacoustic point source is established,and the analytical solution of the sound field is obtained.Then,theoretical models for three types of CNT thin film thermoacoustic transducer array are established respectively,corresponding analytical solutions for sound field are obtained based on the Rayleigh integral.Thirdly,analytical solutions are simplified under typical conditions.CNT thin film thermoacoustic transducer arrays are successfully fabricated in experiment.The frequency response and sound field distribution of the CNT thin film thermoacoustic transducer arrays are measured.The theoretical models and analytical solutions of the CNT thin film thermoacoustic transducer arrays are verified.The effects of the observation point position and the array geometric parameters on the frequency response,directivity and focusing characteristic of CNT thin film thermoacoustic transducer arrays are analyzed.The results show that the three types of CNT thin film thermoacoustic transducer array can effectively emit sound waves in a wide frequency range.The CNT thin film square-matrix transducer array and annular transducer array can generate high directional acoustic beam.The CNT thin film spherical transducer array can generate focused acoustic field.In addition,Three types of CNT thin film thermoacoustic transducer array have specific characteristics: the CNT thin film square-matrix transducer array can adjust the beam direction by phase control;the CNT thin film annular transducer array can effectively restrain the growth of sidelobe amplitude;the CNT thin film spherical transducer array can adjust the size of focal region by controlling the acoustic frequency to meet different requirements in practical application.