Research And Application Of High Sensitivity QCM Precision Sensor

Quartz crystal microbalance(QCM)is an ultra-sensitive sensor that can convert the physical properties of the measured material into equivalent resonant parameters.Due to the advantages of ultra-sensitivity and real-time detection,QCM is widely used in various fields like material characterization,environmental detection,medical diagnosis and food inspection.This dissertation mainly studies the ultra-sensitive QCM sensor.Based on the physical characteristics and vibration characteristics of QCM,the QCM response characteristics under liquid load and viscoelastic load were deeply analyzed,intrinsic sensitive mechanism of QCM was revealed,a response model that can accurately describe the QCM response characteristics under liquid loading and viscoelastic load was established.The main researches and innovations in this dissertation are as follows:1.Based on the piezoelectric constitutive equation of quartz crystal and through the study of the vibration in different electrode regions of QCM sensor,a mass sensitivity acquisition method combining the calculation of mass sensitivity function and finite element simulation was proposed,which essentially revealed the intrinsic mass sensitivity mechanism of QCM.2.The quality sensitivity of porous circular electrode QCM was simulated and analyzed by finite element method,and then the porous circular electrode QCM was prepared by electroplating with customized porous mask plate,and the mass sensitivity of solid circular electrode and porous circular electrode QCM was verified by gas experiment.The experimental results showed that the integral equivalent sensitivity of porous circular electrode QCM is higher than that of solid circular electrode QCM.This work provided a useful reference for improving the sensitivity by changing the shape of electrode.In order to solve the problem that special shaped electrode is difficult to be processed by traditional method,the feasibility experiment of laser etching electrode modification technology was carried out.3.In liquid phase detection,by in-depth study of the classical Kanazawa model and Martin modified BVD model,it was found that the frequency response is related to the product of liquid density and viscosity,which makes it impossible to separate the liquid density and viscosity.In order to solve this problem,a method of measuring the density viscosity of unknown liquid using a single QCM was proposed in this dissertation,and its effectiveness was verified by experiments.4.In order to study the QCM response characteristics under viscoelastic load,the equivalent circuit model of QCM with viscoelastic load was derived by the piezoelectric constitutive equation combined with boundary conditions.The subsequent simulation analysis showed that the QCM equivalent circuit model derived in this dissertation agrees with the classical QCM-D model.In addition,an experiment of blood viscosity measurement was designed to verify the effectiveness and practicability of the equivalent circuit model of QCM with viscoelastic load.Finally,aiming at the problem that the measurement of the dissipation factor in the classical QCM-D model by the instantaneous pulse excitation method is easy to be affected by small external interference,a steadystate measurement method is proposed using the relationship between the dissipation factor and the quality factor.In summary,based on the analysis of mass sensitive mechanism and response characteristics of QCM with liquid and viscoelastic load,the porous circular electrode QCM with higher mass sensitivity than the solid circular electrode QCM was designed in this dissertation.Then the method of separating density and viscosity of unknown liquid by single QCM was proposed,whose effectiveness was verified by experiments.In addition,the equivalent circuit analysis model of QCM under viscoelastic load was derived,and the correctness of the model was verified by comparison with QCM-D and blood viscosity measurement experiments.Finally,aiming at the problem that the instantaneous measurement of dissipation factor is prone to errors caused by small interference,a steady-state measurement method of dissipation factor was proposed.The research in this dissertation has positive significance for promoting the wide application of QCM sensing technology in the field of liquid detection and viscoelastic film detection.