Design And Analysis Of A High Sensitivity Micro-mass Sensor Based On Configuration Optimization

The piezoelectric micro-mass sensor is a novel sensor with the integrated function of excitation and sensing, which is mainly composed of elastic element and piezoelectric element. Due to the characteristics of simple structure, low cost, real-time detection, rapid detection and high measuring precision, it has been widely used in field of chemistry, biomedicine, environment and safety inspection and so on. Sensitivity is one of the key properties used to evaluate the sensor performance. Although it is effective to improve the sensitivity, the miniaturization method can hardly meet the requirements of engineering practicability for the testing difficulties. Therefore, it is of great engineering value to explore new sensitivity improving methods. Based on the comprehensive analysis of the key design factors influencing sensitivity, a new method for improving sensor sensitivity through configuration optimization was proposed, and the relationship between the elastic element configuration and the detection sensitivity was studied. Moreover, the optimization design models for grooved trapezoidal cantilever sensors and multi-stepped cantilever sensors were established to improve the sensitivity. Finally, the feasibility and practicability of the proposed sensitivity improving method was adequately validated by the good agreement between the numerical simulation and experiments. The content mainly includes the following aspects.(1) Optimization model of the micro-mass sensor with grooved trapezoidal cantilever. In order to obtain key factors affecting sensitivity, an analytical model of the sensor is established based on the grooved beam with variable cross-section for detecting concentrated masses and homogeneous distributed masses. With the constraint of keeping the external dimension of the rectangular cross-section cantilever sensor unchanged, a new sensitivity improving method was proposed through simultaneously varying both the surface shape and cross-section of the cantilever. The relationship between the structure parameters of elastic beam and the resonant frequency as well as the sensitivity for concentrated masses and uniformly distributed masses was analyzed. The simulation results show that the change of grooved trapezoidal cantilever’s free end width has little impact on the detection sensitivity of uniformly distributed mass comparing with the concentrated mass detection sensitivity. Finally, an experimental sample was fabricated, and the results show that the concentrated mass and uniformly distributed mass detection sensitivity of the proposed sensor are respectively287.8%and205.2%higher than that of the rectangular cross-section cantilever sensor under the same geometric dimension parameter condition, which verifies the availability of the proposed sensitivity improving method.(2) Sensitivity optimization method for multi-stepped cantilever micro-mass sensors. It can be proved that the sensitivity can be effectively improved by adjusting the stiffness and the distribution of effective mass. Consequently, by defining the step number in the longitudinal direction of the cantilever and the thickness of each segment as design variables, with the goal of maximizing the sensitivity, the optimization design model of multi-stepped cantilever mass sensor was proposed. Ultimately, the influence of the step number on the sensitivity was analyzed. From the numerical simulation results, it can be seen that the sensitivity of multi-stepped cantilever sensor is13.9times of that of the rectangular cross-section cantilever sensor, when the number of segments is9or13,thus validating the effectiveness of the proposed sensitivity improving method.