Research On Surface Acoustic Wave Strain Sensor Based On PMN-PT Piezoelectric Single Crystal

As an important part of the sensor field,the strain sensor has a wide range of applications in practical life,such as urban defense construction,equipment production monitoring,and infrastructure prevention and inspection.At the same time,with the development of flexible devices,strain sensors have broad applications in human-computer interaction,medical health,and human motion detection.At present,there are various types of sensors on the market.Due to the limitation of power and connection cables,the strain measurement scene is subject to many constraints.At the same time,the consistency and cost of strain measurement are also major limiting factors.Among the common strain sensors,SAW strain sensors have attracted much attention because of their wireless passiveness,low cost,good consistency,and low delay.However,the strain sensors made of commonly used surface acoustic wave materials have problems such as limited sensitivity and small strain measurement range.The surface acoustic wave strain sensor fabricated in this paper solves the above limitations,and further explores the conditions affecting the sensitivity of the surface acoustic wave strain sensor.This paper first discusses the types of strain sensors,and chooses to use surface acoustic strain sensors among various sensors.First,COMSOL multiphysics simulation software is used to perform physical field simulations of surface acoustic wave resonators of PMN-PT materials to obtain the frequency of resonance signals..Then the antenna structure is designed and optimized on the HFSS RF antenna simulation software,and a processable antenna is designed.Then use ADS to design and manufacture the matching network of the designed antenna and future surface acoustic wave devices to improve the efficiency of antenna transmission and realize wireless passive measurement.The second major part of this paper is the fabrication and measurement of surface acoustic wave strain sensors based on PMN-PT piezoelectric single crystals.Firstly,a piezoelectric thick film of a surface acoustic wave is produced by a mechanical shearing process,and then metal is deposited on the surface of the produced piezoelectric thick film,and then patterned to produce a surface acoustic wave strain sensor including an interdigital electrode and a reflective grid structure.After making the strain sensor,in order to perform strain measurement,a strain test bench capable of finely and stably controlling the strain parameters is set up.After the comparison,the single-end clamping method with simple structure and stable operation was obtained for strain measurement.The surface acoustic wave strain sensor and the standard strain gauge are located at the corresponding positions of the strain base at the same time,and the resonance frequency of the strain sensor and the strain value of the standard strain gauge are measured in real time.The correspondence between the resonance frequency of the strain sensor and the strain is obtained.The sensitivity of the obtained PMN-PT strain sensor is 1243.5Hz / ??,and the strain measurement range is ± 1000 ??.The article later explains the reason for the high sensitivity.The main reason for the high sensitivity is the extremely high electromechanical coupling coefficient of the piezoelectric single crystal PMN-PT.Finally,the article discusses the changes in sensitivity of PMN-PT surface acoustic wave strain sensors caused by different strain application directions.At the same time,the same process was used to make strain sensors on lithium niobate materials for comparison.Then the reasons for the change of the sensitivity of the surface acoustic wave strain sensor due to different stress application directions are explained.The combined effect of the anisotropy of the piezoelectric single crystal itself and the changes in the physical structure caused by the stress results in a change in sensitivity.