An environmentally friendly multi-step reduced graphene oxide route for flexible transparent conductive strain sensor films

Flexible strain sensors films exhibit significant application potential in the domains of flexible electronic devices, human-computer interaction, and wearable devices , enabling the efficient conversion of external mechanical stimuli into detectable electrical signals. The reduced graphene oxide (rGO) is widely recognized for its excellent electrical conductivity , outstanding mechanical properties, and highly flexibility, making it an ideal conductive material for flexible strain sensors. However, there is a crucial challenge in developing large-scale, eco-friendly, and cost-effective methods for synthesizing flexible sensor films based on reduced graphene oxide . In this paper, a three-step reduction method was firstly designed to prepare a rGO/polyethylene terephthalate (rGO/PET) flexible film with internal reversible three-dimensional conductive network connection for the strain-resistance sensor. Specifically, the three steps involve the reduction of graphene oxide solution using ascorbic acid , the reduction of rGO films prepared by Mayer rod, and the deposition of metal aluminum onto the surface of the graphene film for further reduction. The effect of the correlation between the macroscopic strain and the internal three-dimensional conductive network on the mechanism of strain-resistance sensing was discussed in detail. It revealed that the rGO/PET flexible conductive strain-resistance film sensor presented a gauge factor value up to 15.34 in a small strain range (0.4∼1.5 %), and it exhibited excellent cycle repeatability and stability, indicative by the relative resistance change value of down to 0.2053 after 10,000 cycles. This work not only highlights the three-step reduction method to prepare the rGO/PET flexible conductive film , but also suggests that the film has considerably broad application prospects as a strain sensor.