Investigation of silicone rubber composites reinforced with carbon nanotube,nanographite, their hybrid,and applications for flexible devices

New technology is constantly required for updating new generation flexible devices, such as stretchable sensors, flexible electronics, and actuators. In the present study, a stretchable strain sensor, and actuator were developed based on room-temperature-vulcanized (RTV) silicone rubber reinforced with carbon nanotubes (CNTs), nanographite (GR), and CNT-GR hybrids. A CNT-based strain sensor developed for RTV silicone rubber showed improved stiffness and brittleness. For example, at 5 phr of filler loading, the compressive and tensile modulus for the CNT-reinforced RTV silicone matrix improved by 287% and 240%, respectively. Similarly, the improvements in the compressive and tensile modulus were moderate for the CNT-GR hybrid (210% and 235%) and low for GR (135% and 125%). The improved brittleness resulted in a higher fracture strain of 170% and 155% for the CNT-GR hybrid and GR, respectively. The improved mechanical properties were tested in real-life applications of actuation. The actuation displacement at a filler loading of 2 phr increased to 1.65 mm (CNT), 1.25 mm (CNT-GR), and 0.08 mm (GR). From 2 to 8 kV, the actuation displacement increased by 825% (CNT), 830% (CNT-GR), and 32% (GR). The strain sensor showed a stretchability of >100% (CNT) and >100% (CNT-GR). In addition, the gauge factor was higher for the CNT-GR hybrid composites. The durability measurements showed that the change in resistance was negligible for up to 5000 cycles in both the CNT and CNT-GR rubber composites. A series of experiments confirmed that compared to the composite based on RTV silicone rubber and CNT, the CNT-GR hybrid showed a robust flexibility and stretchability as a piezo-resistive strain sensor and actuator.