Principle Research,Design And Manufacture Of Pressure Sensor Based On Suspended Graphene Membrane

The perception of flow field environment applied on unmanned undersea vehicle is a kind of subversive non-acoustic sensing technology developed in recent years.One of its key technologies lies in pressure sensors with high sensitivity.At the same time,the new fast maneuver fighters and other aerospace equipment also have a strong demand for high-performance pressure test.Due to its excellent mechanical and electrical properties,graphene is expected to be a good sensing material providing critical support for the design of high-performance pressure sensors.For the pressure sensor based on suspended graphene membrane,its mechanism and systematic theoretical guidance for designing lacked and the manufacture is not mature.Therefore,this dissertation studies the pressure-sensing characteristics and piezoresistive effect of suspended graphene membrane,then demonstrates the design and manufacturing process of pressure sensors based on suspended graphene membrane,and finally tests and analyzes the samples of this kind of sensor.The main contents of the dissertation are as follows.1.Aiming at the problem of the lacking mechanism and systematic theoretical guidance for designing pressure sensor based on suspended graphene membrane,the pressure-sensing characteristics and piezoresistive effect of suspended graphene membrane are researched.Firstly,the quantitative relationship between pressure and strain are studied,which is the pressure-sensing characteristics of graphene membrane,using mechanical theory and finite element method to establish the theoretical model and finite element model of pressure-sensing of graphene membrane.Through theoretical calculation and finite element simulation,the paper compares and analyzes the pressure sensing characteristics of graphene membrane in three different shapes(circular,square,rectangular)and different sizes.The result shows that the central deformation displacement and strain of the rectangular membrane are maximum among these three shapes,and both of the central deformation displacement and strain increase with the increasing of membrane size.The gauge factor of graphene is calculated using density functional theory to characterize the piezoresistive effect of graphene membrane,the relationship between strain and rate of resistance change is established,and the applicable range of piezoresistive effect limiting strain to no more than 25% is obtained as well.2.Aiming at the problem of unmature manufacture,the pressure sensor based on suspended graphene membrane is designed and manufactured.Based on the modeling and analysis results of pressure-sensing characteristics and piezoresistive effect,the structure and size of the sensor are designed.Then,the appropriate manufacturing process is selected by analyzing the structure of the sensor,and the process parameters are determined according to the size accuracy of the sensor.Then the scheme of manufacturing process is designed.The key step of the process----design of lithographic mask and transfer of graphene are demonstrated in detail,and the process with corresponding observation results are discussed.Thus the fabrication of the samples is finished.3.The pressure sensor based on suspended graphene membrane is tested and analyzed.The microstructure of the samples is observed by scanning electron microscopy,and the existence of graphene material is verified by Raman spectroscopy.Then,the project for testing the sensors is designed,and the test platform is built.The basic performance of the sensor is obtained through testing and five possible factors which can affect the performance of this sensor are analyzed.The experimental result and comparison show that this pressure sensor based on suspended graphene membrane has high sensitivity.