Experimental Study Of Graphene Strain Sensor Based On Micro-Raman Spectroscopy

Micro Raman spectroscopy(MRS)is regarded as a robust technique for measuring the stress or strain at microscale.The application of MRS is limited in the materials whose have no enough Raman activity and Raman-strain sensitivity.In recent years,the Raman performance of graphene has been well investigated.It is possible to using graphene as a sensing medium for strain measurement,which may provide an effective method of microscale experimental mechanics for the study of the non-Raman active materials or structures.In this work,the performance of graphene strain sensor based on MRS was investigated.The influencing factors on sensing performance,such as range and sensitivity,were studied by experiment,including different substrate types,different crystal types,and different transfer methods.The experimental results revealed that the crystal type of graphene and the substrate thickness had no influence on the range or the sensitivity.Because of the surface and interface properties,the graphene behaved different sensing performance for different substrate materials and different transfer methods.Furthermore,it was proved that the graphene obtained through the traditional wet transfer technique has better sensing performance than that through other existing methods.Then,an improved method is proposed to increase the interfacial stiffness of graphene,enhancing the sensitivity of the strain sensor.Besides,the sensing performance decreased with the increase of the cyclic loading times.The mechanical behaviors of the interface between the single-layer monocrystalline graphene and the polyethylene terephthalate(PET)substrate under tensile strain was investigated by using micro-Raman spectroscopy.The experiments exhibited the evolution of interfacial state between graphene and substrate,including adhesion,sliding and debonding periods,during the uniaxial tensile loading process of PET substrate.Further analyses showed that the stress transfer at the graphene/PET interface controlled by the Van der Waals had obvious scale effect relative to the length of graphene film.Interfacial shear stress(ISS)decreases with the increase of graphene length,while the length of graphene has no effect on the strength limit and stiffness limit of graphene/PET interface.Besides,the interface property was independent on the crystal type of the graphene.