Design And Implementation Of A MEMS Bionic Fish Ear Sensor Structure For Auscultation

Auscultation is the most commonly used clinical test to make a preliminary diagnosis by listening to the sounds emitted by the body’s organs,and its simplicity,efficiency and non-invasive characteristics have made it an enduring test.The stethoscope is the main instrument of auscultation,amplifying the faint sounds emitted by the body.With the development of electronic technology,electronic stethoscopes have gradually replaced mechanical stethoscopes due to their efficient performance.The performance of stethoscopes varies due to the different types of sensors used in different models of electronic stethoscopes.In order to ensure that the electronic stethoscope can capture rich and accurate information,a sensor for stethoscopes is required.In this thesis,a bionic sensor for auscultation is developed based on Micro Electro Mechanical System（MEMS）manufacturing technology.The sensitive structure of the sensor is designed and optimised for the actual needs of the auscultation process to improve its sensitivity and operating frequency band.The overall package is designed to minimise the attenuation of weak sound signals during propagation.Firstly,this thesis investigates the process of sound perception of fish,designs a "fishear" bionic sensor sensitive structure,establishes a mathematical model and performs finite element simulation to theoretically analyse and describe the detection mechanism of the sensor,and investigates the influence of the sensor structure on performance parameters such as sensitivity and frequency response.Secondly,by analyzing the propagation path of the sound picked up by the sensitive structure of the sensor,a theoretical model of three-layer medium transmission is established and simulation experiments are carried out.Castor oil was identified as the encapsulating fluid through the principle of acoustic impedance matching,and E-PTFE film with a thickness of 0.01 mm was selected as the sound transmission membrane for the sensor encapsulation.Finally,the sensor was fabricated by designing a MEMS processing process.An electroacoustic test platform was built to test the performance parameters such as frequency response,linearity and sensitivity of the sensor and the results showed that the designed sensor has better performance compared to an electret microphone.Application tests were carried out on a simulated stethoscope platform with a 3M electronic stethoscope.Different types of heart sound signals collected by the two sensors were analysed in the time and frequency domain.The results show that the signal-to-noise ratio of the sensor is 1 d B higher than that of the 3M electronic stethoscope and that the heart sound information collected is rich and accurate,which is of high value and significance for the development of digital diagnosis and intelligent analysis of diseases.