Carbon-Based Janus Films toward Flexible Sensors, Soft Actuators, and Beyond

ConspectusJanus films have attracted widespread interest due to their asymmetric structure and unique physical and/or chemical properties, demonstrating broad and blooming potentials in mechanical sensing, soft actuation, energy management, advanced separation, energy conversion and storage, etc. Among them, based on the unique features of carbon nanomaterials, extensive efforts have been dedicated to exploiting carbon-based Janus films for high-performance electronic skins, soft actuators, and their integration for smart robotics. Drawing inspiration from nature, biological skins can actively perceive external physical/chemical stimuli and further perform specific motion behaviors. However, there still remain challenges of guided structural design principles, an alternative combination of multifunctions, and advanced synergetic applications. Specifically, their intrinsic properties and related device performances are strongly determined by the functional components' coupling, surface wettability, and controllability of the interface structures. The asymmetric combination of carbon nanomaterials and functional polymers in controllable manners can facilitate the design of high-performance sensing, actuation, and integrated devices, enabling the development of smart soft robotics. Therefore, it is highly desired to summarize this research area of carbon-based Janus functional films for sensing, actuating, and integration as well as to have a deep understanding of the relationship between interfacial structures and their performance for directing future development.In this Account, we will summarize the significant advances in carbon-based Janus films mainly conducted by our group and also discuss the relevant important reported works. We start by introducing the basic properties of commonly used carbon nanomaterials and then discuss the general fabrication strategies for high-performance carbon-based Janus films, including solid-supported physical/chemical approaches and interfacial strategies based on liquid support. Among them, we carefully present the typical combination of two functional components for advanced and synergetic properties. Based on the combined designable functionality, the bioinspired artificial skins that target sensors, actuators, self-sensing actuators, and beyond will be discussed in detail. Finally, challenges and the prospect of structural design, structural interfaces, and integrated functionality will be proposed. We expect that this Account would provide a better understanding of the design, fabrication, applications, and challenges of carbon-based Janus functional films and their significant potential for the development of smart robotics.