Research On Liquid Detection Technology Based On Quartz Crystal Microbalance

As an ultra-sensitive sensor that can translate the small change of system parameters into real-time output resonant frequency change,the emergence of quartz crystal microbalance(QCM)provides a new solution for many scientifical research to build efficient microscopic process online monitoring system,therefore,QCM is considered a powerful tool to decipher the microscopic mechanism and exploring the deep dynamics in many fields such as biomedical,chemistry and materials science.At the same time,thanks to the advantages including ultra-high sensitivity,reat-time output,simplicity of operation,low cost and stable physicochemical properties,QCM been endowed with strong competitiveness and fitness.The application research of QCM in many fields is also on the rise,and because of the continuous improvement of its performance and the emerging of selective adsorption materials,the application fields of QCM technology is keeping expanding.But the study of its own sensitive mechanism and detection model is needing further exploration,these weaknesses have gradually become the key factors that restrict its further development and application.Compared to traditional gasous detection environment,the fluid characteristics of liquid loading make the QCM response in liquid phase become more complex.Therefore,this dissertation is focused on the sensitive mechanism study of QCM in liquid phase,and then bulid a detection model that can describe the QCM reponse under liquid loading more accurately.For the purpose,firstly,this dissertation analyzed the vibration of QCM by solving the quartz crystal piezoelectric constitutive equation,and then acquired the mass sensitivity function by computing the QCM particle displacement amplitudes.These discussions revealed the internal mass sensitive principle of QCM,and then laid the theoretic foundation for QCM applications in many fields.Sencondly,this dissertation revealed the influence of electrode's configuration and size parameters on QCM mass sensitivity function by computing and simulation of three classical configuration QCMs.On the same time,aiming at improving absolute mass sensitivity and uniformity of mass sensitivity distribution,the approaches and realization of targeted optimization of QCM performance according to different actual needs are discussed.A series of gold films electroplating experiments were implemented to verify the results of above simulations and calculations.Thirdly,through detailed discussion of the mass sensitive distribution characteristics and the influence of electrode's configuration and size parameters,the measurement errors caused by neglecting the above two points in Saurebrey equation are quantitatively analyzed.To solve this problem,the QCM mass sensitivity integral average detection model is proposed,and a set of validation experiments verified the practicability and effectiveness of the QCM mass sensitivity integral average detection model compared with the classical Saurbrey equation.After that,through the in-depth study of the classical Kanazawa liquid phase detection model and Martin liquid phase detection model,the "resistance-amplitudefrequency" effect of QCM under liquid load is analyzed and verified according to the modified BVD equivalent circuit,thus revealed the influence of the equivalent dynamic resistance change caused by liquid load on the QCM resonance characteristics.Finally,aiming at the shortcomings of traditional liquid phase detection methods,the effective mass layer effect of QCM under droplet loading is proposed and analyzed,and the deep mechanism of droplet loading affecting the QCM resonant frequency is given.On this basis,combined with the QCM mass sensitivity integral average detection model,the QCM droplet load detection model is established.At the same time,a set of experiments are designed and implemented to verify the effective mass layer effect of droplet load.The experimental results also confirmed the correctness and validity of the proposed QCM droplet load detection model.In summary,through in-depth study of QCM mass-sensitive principle and response characteristics under liquid loading,this dissertation combines the effective mass layer effect of droplet loading with the QCM mass sensitivity integral average detection model,proposed and verified the QCM droplet loading detection model.This model takes the uneven distribution of QCM mass sensitivity and the influence of electrode configuration/size parameters into account,so that it can accurately describe the frequency response of QCM to droplet load.The research results of this dissertation have positive significance for promoting the further development and wide application of QCM sensing technology in the field of liquid detection.