Research On Lamb Wave Resonant Viscosity Sensor Based On AlN Piezoelectric Film

Viscosity is a significant physical parameter in liquid,and it has been widely used in label-free chemical detection,petrochemicals,biomedical and other fields.However,conventional methods for measuring viscosity,such as the falling ball method,capillary method,etc.,tend to require a large volume of liquid or bulky measuring devices,which cannot meet the need for smart and miniaturization.Resonant sensors based on microelectromechanical systems（MEMS）have been proposed for liquid viscosity detection due to their portable size,low cost,easy integration and fast response.Among them,Lamb wave resonant sensors,which perform well in liquid media,are good choices for monitoring viscosity.Although resonant sensors have made great progress in improving the sensitivity,decoupling the density and viscosity and enhancing the liner relationship,the sensor-liquid interaction has not been studied deeply.In this thesis,a two-dimensional sensing model is developed using finite element analysis（FEA）software,which is devoted to the study of the interaction between Lamb wave viscosity sensors and liquid droplets.And a series of experiments are designed to verify FEA results.In viscosity measurements,resonant sensors are susceptible to frequency drift brought about by the influence of liquid morphology,so it is very valuable to study the sensor-liquid interaction.The main contents are as follows.1.The detection mechanism and research progress of various existing viscosity measurement techniques are introduced,and a single-port Lamb wave resonant viscosity sensor based on Al N piezoelectric material is selected.Based on the basic knowledge,previous research experience and simulation analysis,the structural parameters of the Lamb wave viscosity sensor are designed and optimized.Then the device will be processed and prepared using the MEMS process.2.A new two-dimensional viscosity sensing model is proposed based on the finite element analysis method.The dependence of the sensor’s frequency response on the liquid morphology is analyzed by simulation and experimental tests.Both simulation and experimental results show that the liquid loading position,thickness and coverage ratio have an effect on the frequency response of the device.This work allows for more exploration in future research on improving the sensitivity of Lamb wave sensors and reducing experimental errors.3.The frequency response of the sensor to viscosity was performed using glycerol-water mixtures based on a controlled liquid morphology,showing a linear relationship with the square of the viscosity,238.92 ppm/（m Pa·s）^0.5 in simulation and 153.16ppm/（m Pa·s）^0.5 in the experiment.4.The application of the Lamb wave viscosity sensor for detergent residue detection is presented.The design concept of a microfluidic channel is proposed,providing an outlook for subsequent Lamb wave and other acoustic sensors in realizing low-concentration liquid detection.