Reduced graphene oxide/polyurethane composite sponge fabricated by dual-templates method for piezoresistive pressure sensor

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.