The Design Of Nonlinear Micro-mass Sensor

Piezoelectric resonant mass sensors can weigh micro-mass according to the resonance frequency shift induced by the additional mass absorption, which has a great potential in detecting and recognizing biological molecules, small particles, and environmental and water pollutions. Minimizing the geometrical size can significantly improve the sensitivity, and meanwhile, affect the facility of the sensor in usual environment. For example, the nanosized cantilever sensor can only be used in vacuum environment. Therefore, it is necessary to develop new types of mass sensor for harsh environment. In this paper, a new type of micro-mass sensor for weighing and detecting threshold mass is designed by utilizing the bifurcation phenomenon of bistable structure. The paper mainly includes the following parts:(1) a new type micro-mass sensor with the function of weighing mass and switching for threshold mass is designed. By analyzing the influence of excitation load (amplitude, position and frequency) on the dynamic characteristics of the cosine-shaped beam structure, an operation mode switching method between the two functions is proposed by adjusting the excitation load. The influence of mass adsorption position, excitation on sensor sensitivity and minimum detection threshold mass is analyzed. Then, the optimization model for minimizing the minimum detection threshold mass is established. The optimal bistable structural parameters and excitation parameters for achieving the highest detection sensitivity are obtained. The simulation results show that the sensitivity of the proposed sensor enhances 4.25 times compared with both ends clamped beam sensor for weighing mass. By using the advantage of sudden magnitude change induced by additional mass, the mass measuring method can be greatly simplified without impedance analyzer. Also, the minimal threshold mass detection method can be achieved by the counterweight method.(2) a new nonlinear sensor is designed by using the newly proposed built-up beam involving the linear cantilever beam and the nonlinear cosine-shaped beam. The jump frequency detection method based on amplitude mutation is proposed. The measured mass is obtained by finding the jump frequency at which the amplitude changes sharply. It can not only effectively reduce the influence of the environmental damping, but also can simplify the measurement process without the complicated detection circuit. The influence of mass adsorption position, excitation frequency and excitation amplitude on the system jump frequency response is studied, and the optimal combination beam configuration, excitation load and adsorption position with the highest detection sensitivity are obtained.