Carbon nanotube-graphene hybrids for soft electronics, sensors, and actuators

Soft devices that are mechanically flexible and stretchable are considered as the building blocks for various applications ranging from wearable devices to robotics. Among the many candidate materials for constructing soft devices, carbon nanomaterials such as carbon nanotubes (CNTs) and graphene have been actively investigated owing to their outstanding characteristics, including their intrinsic flexibility, tunable conductivity, and potential for large-area processing. In particular, hybrids of CNTs and graphene can improve the performance of soft devices and provide them with novel capabilities. In this review, the advances in CNT-graphene hybrid-based soft electrodes, transistors, pressure and strain sensors, and actuators are discussed, highlighting the performance improvements of these devices originating from the synergistic effects of the hybrids of CNT and graphene. The integration of multidimensional heterogeneous carbon nanomaterials is expected to be a promising approach for accelerating the development of high-performance soft devices. Finally, current challenges and future opportunities are summarized, from the processing of hybrid materials to the system-level integration of multiple components.