Modeling and Experimental Characterization of Flexible Graphene Composite Strain Sensors

In this paper we introduce the theoretical and experimental investigation of piezoresistive graphene-composite strain sensors on Si substrate. The graphene band structure in response to the applied strain was modeled using tight binding analysis. The simulation showed that the graphene band gap opened up to 1.4 eV in response to strain leads to an appreciable change in film resistivity, which can be related to the increase in gauge factor (GF). Furthermore, the usage of flexible substrate leads to a significant increase in gauge factor by integrating the piezoresistive response of the Si thin layer, thus magnifying the overall GF response. Furthermore, FEM analysis showed combined longitudinal, transverse, and shearing strains in the graphene lattice as a result of the applied tensile strain. Therefore, the combined strain effects have to be incorporated in the analysis for better estimation of the sensor GF.