Three-dimensional Interfacial Stress Sensors Based on Graphene Foam

Author:Yang Jia Zuo

Supervisor:li xiao ping lv xiao zhou


Degree Year:2019





With the continuous development of pressure measurement technology,pressure sensors are widely used in medicine,robotics,aerospace,and industrial production and other fields.When a pressure is applied on the surface of an object,the contact surface will be suffered the same magnitude stress in the opposite direction of,known as the interface stress.According to the direction of action,such pressure can be divided into two types.The pressure perpendicular to the interface is called vertical stress(usually one-dimensional,denoted by z-direction),and the pressure parallel to the interface is called shear stress(usually two-dimensional,denoted by x-direction and y-direction).In practical application,most of the pressure is neither perpendicular to the interface nor parallel to the interface but coupled with Z positive pressure,X and Y shear force,which is called three-dimensional interface stress.Therefore,it is of great scientific significance and urgent practical value to decouple the three-dimensional interface stress into one-dimensional vertical stress and two-dimensional shear stress.In order to understand and measure this 3D interface stress,a graphene foam with high-pressure sensitivity was designed and prepared.Based on this graphene foam,a new 3D interface stress sensor was designed,which can measure the direction and magnitude of 3D interface stress in real time and stable.The specific research content and innovation points are as follows:1.A graphene foam with high pressure sensitivity was prepared based on polyimide foam.In order to meet the demand of high sensitivity of three-dimensional interface stress measurement,a graphene foam based on polyimide was proposed.Due to the use of polyimide foam as a template,the foam can be self-supporting,with excellent mechanical properties,the elastic modulus of up to 5 kPa.In the process of reduction of graphene oxide used the chemical and thermal reduction,the foam has good electrical properties,conductivity of 0.4 S/m.By adjusting the preparation parameters of the graphene foam,realizing the high pressure sensitivity and can be up to 0.36 kPa-1.2.A highly sensitive 3D interface stress sensor was designed based on graphene foam.In order to solve the problem of low sensitivity,we designed and fabricated the 3D interface stress sensor based on the high sensitivity of graphene foam,which has high 3D interface stress sensitivity.Measurement range at the direction of positive pressure can reach0 kPa-50 kPa,the sensitivity of 0.0270 kPa-1,in the direction of the shear force measurement range can be up to 0 kPa-25 kPa,the sensitivity of 0.0169 kPa-1.3.A 3D interface stress testing platform was built.In order to test the 3D interface stress sensor,we built a 3D interface stress testing platform based on the 3D displacement platform and the digital high sensitivity gauge meter.The displacement range of the 3D interface stress testing platform in the direction of positive pressure is 0 mm-10 mm,and that in the direction of shear force is 0 mm-6.5 mm,with a precision up to 0.02 mm.The magnitude of the measurable force in the direction of positive pressure and shear force is 0 N-5 N,and the accuracy is 0.001 N.4.A novel 3D interface stress sensor based on high pressure sensitive graphene foam was designed.The new structure enables the measurement of vertical stress and shear stress without crosstalk.The measurement range of this sensor in the direction of the vertical stress can reach 0 kPa-21 kPa with the sensitivity of 0.029 kPa-1,the measurement range in the shear stress direction is 0 kPa-12.5 kPa with the sensitivity of 0.020 kPa-1,0.019 kPa-1,0.018 kPa-1,0.019 kPa-1.5.The fabrication process of a new 3D interface stress sensor based on graphene foam was studied.The fabrication processes of the new 3D interfacial stress sensor based on graphene foam includes physical and chemical reduction,flexible circuit board,the preparation of graphene flexible wire,conductive silver glue electrodes,the mold of polydimethylsiloxane device,half prepared by curing polydimethylsiloxane devices bonding process.6.The decoupling method of a novel 3D interface stress sensor based on graphene foam was studied.The state of the new 3D interface stress sensor structure based on graphene foam under different 3D interface stresses was analyzed,and the 3D interface stress decoupling model was established.The experimental data were obtained through the experiments,and the data were put into the model to solve the unknown parameters.The decoupling method of a new type of three-dimensional interface stress sensor based on graphene foam was obtained.By this decoupling method,the sensor can realize the real-time measurement of three-dimensional interface stress without crosstalk.