Simulation Research On High Quality Factor Sensing Performance Based On Two-dimensional Phononic Crystal

Phononic crystal is a new type of artificial composite periodic structure with a phononic bandgap.Because of its bandgap and defect state characteristics,it provides a great opportunity for the design of many new acoustic devices such as phononic crystal sensors,phononic crystal decomplexers,etc.This dissertation uses the finite element method to focus on the two core issues of designing a new high-quality factor phononic crystal sensor and designing a phononic crystal decomplexer.Taking acetone solution as an example to analyze the performance of the sensor and give the sensitivity of the sensor to the acoustic impedance,and further analyze the influence of the gradient chamber and liquid viscosity on the performance of the sensor.In addition,a phononic crystal decomplexer was designed by introducing a whispering gallery structure,and its decomplexing performance was studied.Firstly,a new type of phononic crystal sensor for solution concentration sensing was designed by using the defect state characteristics,and the sensing performance parameters corresponding to different concentrations of the sensor when sensing acetone solution were calculated in this dissertation.The transmission spectrum of the sensor was simulated by the finite element method.The high-quality factor of 45,307.29 and sensitivity of 80,133.33 Hz were obtained for the acetone concentration of 1-9.1%,and the quality factor of 45,345.83and sensitivity of 24,410 Hz were obtained for the acetone concentration range of 10-100%.To verify the application of the sensor to sensing other solutions,the sensitivity for sound velocity and density was calculated as 24.61 m^-1 and 0.7764 m³/（kg·s）,respectively.It indicated the sensor was sensitive to acoustic impedance changes of the solution and equally suitable for sensing other solutions.The effect of different numbers of gradient chambers on sensor performance was analyzed,and it was found that with the increase of the number of gradient chambers,the effect of acoustic energy convergence becomes better,and the quality factor of the sensor increases,but this makes the sensitivity of the sensor decrease continuously.In order to make the simulation calculation closer to the actual experimental test,the influence of the viscosity of water and mercury on the performance of the phononic crystal sensor was also studied.Through calculation,it was found that the peak value of each transmission peak decreased after the liquid viscosity was added,and the frequency shifted to a certain extent.However,the concentration of the acetone solution can still be judged by the different frequencies corresponding to the peaks in the transmission spectrum.This thesis further designs a phononic crystal demultiplexer using defect state characteristics with a whispering-gallery modes structure.By changing the rotation angle of the upper cup and the thickness of the cup wall of the whispering-gallery modes structure,the regulation of different phononic crystal band gaps is achieved,resulting in multiple defect states to verify the feasibility of the demultiplexer designed by this structure.This thesis mainly utilizes the high symmetry and high degree of freedom of various parameters of whispering-gallery modes structure to achieve the design of multiple resonance frequency demultiplexing channels with the same structure and discovers that this structure has great advantages in anti-interference of phononic crystal demultiplexers.The research of this thesis provides theoretical guidance for the design of phononic crystal sensors,a new type of biochemical sensor,making it closer to the requirements of actual production and use.It also provides optimization ideas and model references for the design of phononic crystal demultiplexers.