| With the development of mobile Internet,Internet of things,and wearable electronic devices,new biochemical sensors have been required to be high sensitivity,miniaturized,and chip-integrated.Using micro-electromechanical systems(MEMS)technology to manufacture highly sensitive and highly integrated miniature sensors is a trend in the field of sensors.As a kind of high-frequency electroacoustic device based on MEMS technology,Film Bulk Acoustic Resonator(FBAR)has attracted more attention in recent years and has wide application prospects in the field of biochemical sensing,with the advantages of high working frequency,small size,high sensitivity,and integration with CMOS.However,most of the reported longitudinal-wave mode FBAR sensors have a significant loss of performance in the liquid-phase testing environment,which limited their higher sensitivity of trace materials.The development of shear wave resonance mode FBAR devices is an effective method to solve this problem.In this paper,based on the application demand for the high sensitivity and integrated biochemical sensor,to solve the key problems that restrict the wide application of FBAR devices,the sensitivity principle,structure design,manufacturing method and application characteristics of shear-mode FBAR sensors are studied,and a scheme to effectively stimulate shear wave resonance is presented.The sensitivity rules of the micro-nano scale shear-mode bulk acoustic wave to its viscous interface are given experimentally for the first time,which provides a high-performance detection platform for liquid-phase biochemical online analysis.In addition,an example of blood rheology dynamics based on a shear mode FBAR is reported.1.Based on piezoelectric theory,a coupled model of excitation field and piezoelectric film body acoustic wave propagation is established,and the propagation law of bulk acoustic wave under the condition of the angle between excitation electric field and polarization axis is studied.By the transformation of the coordinate system,a matrix form of the short circuit elastic stiffness constants of the AIN thin film with a c-axis tilted orientation can be obtained.By solving the Christoffel equation under lateral electric field excitation,the theoretical approach of shear resonance using inclined c-axis-oriented and transverse electric field excitation in ZnO and AIN FBAR devices is verified.2.Based on the transmission line model combined with piezoelectric equations,a design scheme of shear mode FBAR devices using tilted c-axis piezoelectric films is studied,and the theoretical expression of resistance and liquid-phase viscous sensitivity of these devices are obtained.The impedance characteristics of the device in different viscous liquid environments are analyzed by numerical calculation,and the viscous load response law of the resonant structure is revealed,and the relationship between the tilt angle of the piezoelectric polarization axis and the viscosity sensitivity of the device is found.After the optimization of the model,the viscous sensitivity of ZnO FBAR is calculated to be in the range of-2.25 to-2.0×10-5 Hz·kg·m-3Pa·S-0.5,and the viscous sensitivity of AIN FBAR is in the range of-5.9?-5.5×10-5 Hz ·kg·m-3 Pa·S-0.5.3.According to the requirement of Q value,sensitivity and stability of the device operated in liquid-phase environment,the method and effectiveness of the application of lateral-electric-field excitation shear mode are verified based on piezoelectric theory.The finite element model is established to simulate the excitation electric field and vibration modes,and the optimal design relationship between the critical structure parameters and the device performance is determined.Actual devices are prepared by MEMS process,and the basic laws of these devices on the viscous surfaces are given for the first time at home and abroad,which intensifies the understanding of the viscous damping effect of micro-nano piezoelectric resonant structures and provides basic data for biometric applications.4.For the application requirements of medical detection to micro blood analysis equipment,based on the deep understanding of the liquid phase viscosity sensitivity characteristics of shear mode FBAR,a blood rheology analysis sensor based on a shear mode FBAR is designed according to the changes in density and viscoelasticity during blood coagulation.The clinically significant blood coagulation physiological indicators are obtained,and the principle and application feasibility are verified.The device exhibits excellent measurement repeatability and consistency with standard hemagglutination testing methods.Meanwhile,the test results revealed changes in the blood enzymatic cascade and fibrin polymerization under different conditions,providing more information for pathological interpretation of exogenous coagulation mechanisms. |
PDF Full Text Request