Research On Novel Acoustic Impedance Matching Layers For High-Frequency Ultrasonic Transducer

Ultrasound has been widely utilized in numerous areas such as diagnostic imaging,micro-particle manipulation and cellular stimulation due to its low price and high security.With the development of medical technology and serious requirement for medical treatment,it is urgent to achieve medical diagnostic machine with higher performance.Ultrasonic transducer,as the core component of diagnostic machine,has attracted much attention.Fabricating ultrasound transducers of high voltage sensitivity and wide bandwidth is always a research of great significance.In this paper,we focused on the improvement of transducer performance and designed a new acoustic impedance matching layer of ultrahigh frequency transducer after deep investigation.We firstly analyzed the principle of ultrasound transmission by wave motion equation.Many parameters such as characteristic acoustic impedance,reflection coefficient and attenuation were listed.Meanwhile,we also introduced the ultrasonic transducer on the view of material and structure.The parameters of materials such as piezoelectric effect,elastic coefficient,dielectric coefficient and piezoelectric coefficient were included.The core element of ultrasound transducer,equivalent circuit model,the design criterion and the characterization of transducer were deeply studied for investigation of transducer structure,which provided the theoretical foundation for the design of ultrasonic transducer with high sensitivity and performance.A new acoustic impedance matching layer for ultrahigh ultrasound transducer was designed and fabricated based on the transmission theory and Mason Model,which achieved three times voltage magnitude improvement.Also,the bandwidth of transducers increased from 36.9%to 89%,which made the resolution of the transducer perform better.There are two innovation points of our work:1.Current theory is based on analogy explanation of single matching layer rather than the analysis of the whole transducer.The specific assumption conditions limited the choice of transducer material.Our work focused on the two ports equivalent network of matching layer and the performance analysis of the whole transducer.2.In our work,physic sputtering and chemical deposition were applied,which improved the accuracy of fabrication compared with the traditional process.