Design And Sensing Behavior Research Of Graphene-based Flexible Sensors

Nowadays,many companies are committed to the"Internet of Things"construction.Therefore,the industry of wearable devices develops rapidly.Among them,flexible sensors as an important part of the wearable industry set off a global research boom.However,there are still many problems with the development of flexible sensors in practical applications.For instances,the ductility of metal materials,the stability of organic materials,the conductivity of inorganic materials are poor,1D structured sensors are more suitable for small deformation,2D structured sensors have narrow measurement range,and 3D structured sensors are more suitable for large deformation.These disadva ntages make them difficult to be practical application.The graphene-based materials with excellent electrical conductivity,predominant mechanical properties and high light transmission are ideal sensitive materials.In this paper,two kinds of flexible sensors based on graphene materials are designed,which are both suitable for the detection of large deformations as well as small deformations,and show high sensitivity.The main contents of this thesis are as follows:1.As-prepared copper nanowires are mixed with GO,and the 3D gel is prepared by hydrothermal reaction,followed by crushed and constructed flexible sensors.Copper nanowires can improve the conductivity of rGO and change the contact modes of rGO by increasing the conduction paths,which enhances the sensitivity of the sensors.The flexible sensors possess a wide detection range of strain up to 70%with the guage factor of 26.After more than 1000fatigue tests,the hybrid sensors can still maintain good sensing performance.The sensors can detect not only small deformation such as wrist pulse vibrations,but also large deformation like the elbow movement.Moreover,the film sensors can be used for lip movement test to realize the function of lipreading recognition.2.Graphene solution is dripped on the PDMS film with micropillar arrays.After drying,two pieces of graphene/PDMS films are mated to each other to construct flexible interlocked sensors.The contact surface of graphene is adjusted by the microarrays and the roughness of graphene.The effects of pitch sizes of micropillars,the dropping amount of graphene and interlocking modes on the conductivity and the sensitivity of sensors are examined.The sensors can respond to tension,pressure,bending,shear forces and have a sensitivity of 10.41 kPa^-1under 300 Pa.The interlocked micropillar sensors have excellent stability which can afford over10,000 loading-unloading tests and very short response time less than 19 ms.What's more,the heterogeneous sensors can distinguish various human motions.Compared with face-to-face planar sensors and single micropillar sensors,the interlocked sensors can realize multi-peak detection more detailed,which is meaningful to medical diagnosis and health monitoring in future.In addition,the sensors can differentiate different concentrations of ethanol and can undertake spatial stress distribution.