Investigations Of A Bulk Acoustic Wave Sensor With A Microfluidic Channel

This thesis studies the bulk acoustic sensor with a microfluidic channel, in which the outline and the conclusions of the thesis are arranged in the first chapter and the last chapter, respectively. The main research contents are divided into four parts which include:(1) Related theories in the study of film bulk acoustic resonators; (2) Optimization of the acoustic liquid sensor and acoustic energy regulation; (3) Temperature compensated of acoustic liquid sensor and acoustic energy regulation; (4) Acoustic energy regulation and the study of sub-harmonic waves excited by a nonlinear impact structure. The corresponding contents of above parts as described as following:1. Related theories in the study of film bulk acoustic resonatorsIn the second chapter of the thesis, several common methods of studying FBAR were described, then we specially calculated the structure based on the high over-tone bulk acoustic resonator (HBAR) by Mason model and transfer matrix method, in which the input impedance was calculated and the impedance spectrum was analyzed.2. Optimization of the HBAR liquid sensor and acoustic energy regulationIn the third chapter of the thesis, firstly the acoustic liquid sensor was introduced. Then, the optimized HBAR liquid sensor structure was designed by the regulation of acoustic energy. Meanwhile, we investigated the performances of the sensor by Mason model and transfer matrix method, and the Q versus the Si substrate was calculated. Finally, the structure of the acoustic liquid sensor was optimized by the calculated results.3. Temperature compensated acoustic liquid sensor and acoustic energy regulationIn the fourth chapter, we discussed the influences of the temperature variation on the liquid sensor. A sensor structure with a compensation layer was designed. Then the performances of the structure was analyzed by Mason model and transfer matrix method, in which the influences of the Si thickness on Q of the sensor were investigated, and the influences of the compensation layer thickness on the TCF and Q of the sensor were analyzed. According to the calculated results, the structure of the temperature compensated liquid sensor was optimized.4. Acoustic energy regulation and the study of sub-harmonic wave based on a nonlinear impact structureIn the fifth chapter, a nonlinear impact structure was designed which could be described by the simplified model with two spring-mass oscillators. Then we used finite element software COMSOL to simulate the structure and investigate the collision process. Firstly, the transmitted sound pressure versus the frequency variation was calculated to show the frequency spectrum of the transmitted sound. We found that the nonlinear oscillation could control the existence of sub-harmonic wave.Finally, the conclusions and the prospects of the work were presented.