Wearable sensors with highly flexible and sensitive characteristics have attracted research interests in the promising field of electronic skin, health monitoring, and soft robotics. However, the developing of high-performance piezoresistive sensor is full of challenges due to the expensive equipment and complex procedures. Herein, we fabricate a reduced graphene oxide/ polyurethane composite sponge (GPCS) pressure sensor combining with dual-templates. The polyurethane (PU) sponge provides an elastic structure as solid template. Meanwhile, air bubbles as gas template are used to uniformly disperse graphene oxide (GO) sheets. The burst of air bubbles in the process of thermal treatment makes GO coating on the surface of PU skeleton, avoiding the aggregation of reduced graphene oxide. Therefore, the GPCS exhibits excellent compressibility and uniform coating structure. As a result, it also possesses high sensitivity (Gauge Factor = 3.00 in the range of 0–10% strain), fast response time (35 ms), and excellent cyclic piezoresistive stability (5000 loading–unloading cycles) when applied in the pressure sensor field. Moreover, the flexible wearable stress–strain sensor assembled by the GPCS can be easily adhered on the surface of human skin and precisely detect human movements such as elbow bending and finger bending. Such low-cost procedure and excellent sensing performance enable GPCS sensor to demonstrate tremendous application potential in the field of advanced wearable devices.

Reduced graphene oxidepolyurethane composite sponge fabricated by dual-templates method for piezoresistive pressure sensor
    Abstract
    1 Introduction
    2 Experimental section
        2.1 Materials
        2.2 Preparation of reduced graphene oxide–polyurethane composite sponge
        2.3 Fabrication of GPCS-based sensors
        2.4 Characterizations
    3 Results and discussion
        3.1 Morphological and structural study
        3.2 Mechanical performance
        3.3 Pressure sensing properties of GPCS-LAA
        3.4 Sensing application of GPCS-LAA as a wearable sensor
    4 Conclusion
    Acknowledgements 
    References

• Jingwen Zhang(School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China) Corresponding author
• Lian Liu(School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China)
• Jiao Liu(School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China)
• Yanbin Zhu(School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China)
• Gang Kong(School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China)
• Zijing Ou(School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China)
• Delin Lai(School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China)
• Shuanghong Zhang(Guangzhou Special Pressure Equipment Inspection and Research Institute, Guangzhou 510663, China)
• Chunshan Che(School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China)