Research On Design Theory And Application Of Miniature Medical Ultrasonic Transducers

The micro ultrasonic transducer has a broad application prospect in the ultrasonic endoscope,intravascular ultrasound,and other fields.The design and preparation of micro transducer as well as its performance optimization and evaluation method are the key challenges.Therefore,it is of great significance to systematically study the design and preparation methods of the micro-ultrasonic transducer and evaluate the influence of key preparation parameters on its performance.Aimed at the above problems,this thesis focuses on the design theory and application of the micro ultrasonic transducer.The contents are as follows:1.The effects of piezoelectric materials,matching materials,and backing materials on the performance of transducers are studied.The vibration modes of the transducer such as the thickness stretching mode and length stretching mode are then analyzed.The impedance characteristic and electrical matching method of the transducer are proposed.The performance evaluation methods are introduced and a systematical simulation method is proposed and discussed.2.Size effect of the micro transducers is studied to enhance its performance.The influence of the size effect on transducer impedance and acoustic characteristics is systematically analyzed by the simulation models.The results of simulation analysis and pulse echo show that the simulation model established in this paper can be used to accelerate the design of the micro transducer.By optimizing the size parameters,the performance of the transducer can be further improved.This method will provide a new idea for the design of the micro-ultrasonic transducer.3.Ultrasonic endoscope microprobe transducer with working frequency 20MHz and 12MHz were developed.The results of pulse-echo test,sound field measurement and imaging suggest:By using the simulation design and optimization method proposed in this paper,especially by adding reasonable matching circuit design,the developed miniature endoscope ultrasonic transducer has good performance and can well meet the requirements of ultrasonic endoscope imaging4.Micro piezoelectric transducers are applied in two-dimension acoustic focusing for performance enhancement in a conventional hydrodynamics flow cytometer.The sample stream width and maximum throughput in this work is better than previous work.And this method can reduce particles clog-up in high sample concentration by keeping particles away from the wall of the tube.This technology will be of great significance for rare cell detection in large volumes such as circulating tumor cells detection.5.Miniature transducer with center frequency 42.9 MHz are applied in material acoustic properties measurement.Acoustic parameter evaluation method is analyzed according to the theory of sound propagation.Six materials including liquids(water,liquid paraffin),polymer(TPU,polyimide)and ceramics(PZT-5H,Alumina)are measured.This technology will be of great significance in applications such as high frequency medical imaging.Through the above works,the existing design theory of transducer is perfected,and a design method of micro transducer is proposed.The applications of micro transducer have been broadened.These works are of great significance in the developing of micro transducers.