Cellular Graphene: Fabrication, Mechanical Properties, and Strain-Sensing Applications

We provide a review of cellular graphene (CG), from its fabrication, to characterization of mechanical properties, to applications in strain and pressure sensing. Although several recent reviews have briefly surveyed various types of strain and pressure sensors fabricated from common one-dimensional or two-dimensional (2D) nanomaterials such as carbon nanotube (CNT), graphene, and metallic nanowire/nanoparticle, the emerging applications of CG in the design and development of strain and pressure sensors, as well as the structure-property-function correlations in sensing performance, have not been systematically covered. CG exhibits unique strain-sensing capabilities that collectively enable a wide range of strain sensing to be achieved. We first review several state-of-the-art approaches for fabricating CG with emphasis on the engineering of tailored mechanical properties. Second, the strain- and pressure-sensing performance of CG-based devices against a range of fabrication processes is systematically and critically analyzed. Along the way, representative applications of such CG-based sensors are thoroughly discussed. This review aims to provide basic information for the design of novel CG as well as other classes of three-dimensional porous structures fabricated from various 2D nanomaterials. In the conclusion, we highlight the extension of design principles to other 2D materials and critically summarize the key issues that need to be addressed in the future. Excellent strain- and pressure-sensing performances, such as large dynamic range and ultrahigh sensitivity, have been demonstrated by sensors made of cellular graphene, attributed to various fabrication techniques and derived mechanical properties. However, major challenges remain in the development of cellular graphene-based strain and pressure sensors, which include precise control on cellular structure, durability and stability, and differentiating multideformation modes. In this review, the fabrication of cellular graphene is first summarized, with emphasis on the engineering of their mechanical properties. Recent advances in the design of cellular graphene-based strain and pressure sensors are then presented, with their advantages and problems critically analyzed. Future research efforts should focus on in-depth understanding of structure-property-function correlations of cellular graphene-based sensors and generalization of the design principles to the fabrication of other two-dimensional materials-based sensors. Graphene, as the most well-known 2D material, can be assembled into amazing cellular architectures. These cellular graphenes show excellent performances (i.e., large sensing range, ultrahigh sensitivities) in strain- and pressure-sensing applications based on their highly tunable mechanical properties. Cellular graphene has become a promising sensing material for the development of flexible and wearable strain and pressure sensors.