Investigation of graphene piezoresistors for use as strain gauge sensors

The primary objective of this research is to fabricate a graphene-based piezoresistive strain gauge and characterize its sensitivity. The strain gauge consists of mechanically exfoliated graphene sheets and electrical electrodes located on a silicon wafer. Instead of using e-beam lithography, which is the most widely applied methods in experimental studies of graphene, a new fabrication method utilizing conventional photolithography was used to easily fabricate a new nanoelectromechanical system strain gauge. The proposed fabrication technique is easy and only requires a few types of microfabrication equipment, thereby opening up a new way to broadly spread and facilitate associated graphene research, especially for those laboratories with limited resources. To characterize the piezoresistive sensitivity of the graphene-based strain gauge, a strain-detection system built by an equivalent-stress macrocantilever was set up to generate mechanical bending strain where a calibrated commercial strain gauge was packaged to display the generated strain. Utilizing this measurement setup, the electrical properties of the graphene-based piezoresistive strain gauge were reliably investigated. A high gauge factor of ∼150 was experimentally measured with the graphene device, which promises a new strain gauge of high sensitivity.