Graphene-based strain sensors have attracted tremendous interest due to their potential application as intelligent wearable sensing devices. However, for graphene-based strain sensors, it is found that the sensing property at the beginning of the tensile cycle is not stable. Concretely, the peak resistance value gradually declines in the first dozens of cycles in every cyclic test. This is a problem that obviously affects the measurement accuracy but is rarely investigated so far. In this paper, this phenomenon is for the first time systematically studied. According to the reliable experimental results, it can be concluded that the decline of resistance is caused by the evolution of wrinkle morphologies in the graphene layer, which is essentially attributed to the temporary slippage of the graphene sheets under external stress. Based on the analyzed mechanism, a targeted improvement solution was proposed and verified. By the combined effects of polydopamine and Ni2+, the slippage among the rGO sheets was suppressed and a strain sensor with excellent sensing stability was obtained as expected. Furthermore, the sensitivity of the modified sensor was six times higher than that of the pristine one due to the change in the crack form, demonstrating it to be an effective method to obtain a graphene-based strain sensor with comprehensively high performance.
Keywords: cycling stability; graphene; high sensitivity; microstructure; strain sensor.