Research On Improving The Sensitivity Of Micro-mass Sensor Based On Piezoelectric Cantilever

Piezoelectric cantilever micro-mass sensors (PEMS) are based on piezoelectric effect, which are primarily composed of piezoelectric elements and resonator. While target particles are attached to the detecting area of the sensor, the micro-mass of the target particles causes the resonance frequency shift of the sensor, the mass or density of target particles could be obtained quantitatively through detecting the frequency shift. PEMSs are widely used in microorganism detection and identification, atoms weighing, biological and chemical detections as they can provide the advantages of self-exciting, self-sensing, real-time, in-situ, and in liquid detection with high sensitivity. In recent years, with the piezoelectric cantilever micro-mass sensor applications more widely, it’s necessary to improve the sensor’s sensitivity in order to meet the testing requirements of precision in quantitative analysis, fluid environment detection et al. In this article, the improved methods of the sensitivity and quality factor of the sensor are presented and developed by designing the resonator structure and using high-order resonant mode et al. according to the different test environments and test requirements. The research contents and achievements of this thesis are as follows:(1) Theoretical analysis of piezoelectric cantilever. Basing on the vibration theory of unimorph cantilever, the theoretical model of the sensor was established and the sensor’s vibration wave form, resonance frequency, mass detection sensitivity and quality factor are also obtained, which have great influence on the sensor’s performance.(2) Proposed a new method to improve the sensor’s mass detection sensitivity through optimizing the cross-section of the sensor. The folded V-shaped cantilever sensor was designed and the theoretical model was established. Then, the sensitivity was analyzed through finite element simulation and experimental methods. Influences of the structural parameters of the V-shaped cross-section micro-cantilever sensor on the sensor’s sensitivity were discussed.(3) Another proposed design method of resonance micro-mass sensor is excited high resonance mode of the sensor. The analysis model was established; the sensor basing on the fourth order mode was designed and fabricated. The simulation and experiments results indicated that the high order mode sensor has higher sensitivity compared with the fundamental mode. Influences of the structural parameters such as length ratio and thickness ratio of the extension layer of micro-cantilever sensor on the sensor’s sensitivity were discussed. (4) In the field of liquid measurement, a new micro-channel liquid concentration sensor based on micro-cantilever was developed to improve the sensitivity of the sensor by using circuitous micro-channel effectively extending the sensor’s most sensitive areas and eliminating the damping effect of the liquid on the sensitivity and resolution of the sensor.The thesis has studied the methods to improve the sensor’s sensitivity through finite element simulation and experiments, and verified the feasibility and effectiveness of these methods. The thesis provides a new way to study the piezoelectric micro-cantilever sensor.The work was supported in part by the National Natural Science Foundation of China under Grants11372063. The financial contributions are gratefully acknowledged.