Application of Carbonene Materials for Artificial Muscles

The development of new types of artificial muscles is of utmost importance as traditional actuators based on mechanical drive systems no longer meet the stringent requirements of flexibility, high efficiency, and multi-stimuli responses in advanced functional fields, such as soft and biomimetic robots, sensors, artificial intelligent control, and artificial intelligence. Carbonene materials refer to carbon materials composed of all carbon atoms with sp² hybridization, mainly including carbon nanotubes and graphene. Owing to their exceptional properties such as light weight, excellent mechanical performance, high conductivity, flexibility, and large specific surface area, carbonene materials demonstrate significant application potential in artificial muscles, thereby promoting the rapid development of corresponding fields. Herein, the recent progress of the application of carbonene materials in artificial muscles is summarized to provide a comprehensive understanding of the preparation, properties, and applications of artificial muscles composed of carbonene materials. First, carbonene artificial muscles integrating response, actuation, and structure are introduced. As carbonene materials are unique building blocks that can be readily assembled into macroscopic materials with various structures, fibrous and membranous artificial muscles based on carbonene materials are discussed in detail. Carbonene fiber actuators demonstrate diverse actuation performances when fabricated with different structures. Bending actuation typically occurs when carbonene artificial muscles with asymmetric structures are subjected to external stimulation. The untwisting of carbonene artificial muscle fibers with twisted structures causes torsional and tensile actuation, which can be attributed to the volume expansion induced by external stimuli. Furthermore, coiled structures achieved by twisting a fiber until it is fully coiled can enhance the actuation stroke. Thus, the actuation of artificial muscle fibers made of carbonene materials can be classified into bending, rotation, and contraction actuations. Second, carbonene materials have long been considered as a functional component in composite materials for specific applications owing to their excellent physical and chemical properties. Therefore, the application of carbonene materials as an additional component to other artificial muscle materials (such as smart hydrogels, dielectric elastomers, and conducting polymers) is reviewed. By employing carbonene materials, artificial muscle materials exhibit improved electrical and mechanical properties, thereby leading to superior actuation performances. In addition, integrating carbonene materials into artificial muscles can endow the muscles with programmable actuation and sensing functions. Finally, the challenges faced in the application of artificial muscles based on carbonene materials and the future application of carbonene artificial muscles with multi-functional actuation performance are briefly discussed.