Tunable Auxeticity in Hydrogenated Carbon Nanotube Origami Metamaterial

Inspired by the origami architecture and the progress in the functionalization of carbon-based nanomaterials, we design a carbon nanotube origami (CNT-O) metamaterial with the assistance of hydrogenation and by utilizing molecular dynamics simulation. The mechanical properties, including stiffness, ultimate strength, failure strain, and Poisson’s ratio, are systematically studied. Our findings show that the mechanical properties of CNT-O can be tuned and programmed by altering the underlying topological parameters and adopting surface functionalization. We resort to computational simulation, theoretical analysis, and experimentation to demonstrate that an extremely broad range of strain-dependent and scale-independent negative Poisson’s ratio can be achieved for nanoarchitected metamaterials, mainly driven by the kinematics of the folding/unfolding in origamis. The proposed origami strategy imparts a platform for designing the next generation of low-dimensional nanomaterials (e.g., graphene and CNT) with highly tunable auxeticity. Carbon nanotubes (CNTs), the classic one-dimensional material, were uncovered in 1991 and reported to be made out of a single graphene layer later in 1993. Since these discoveries, the carbon-based materials have attracted intensive research interest due to their outstanding thermo-electro-mechanical properties. To expand their range of applications and overcome their shortcomings such as brittleness and low-dimensional feature, many engineering strategies have been proposed to modify their properties. Inspired by the ancient art of paper folding, we first construct the CNT origami with a Miura-ori tessellation via surface functionalization using hydrogen atoms and then resort to molecular dynamics simulation, theoretical analysis, and experimental test to demonstrate that the origami strategy can provide a platform for designing CNTs with enhanced stretchability, high strength, and scale-independent strain-dependent negative Poisson’s ratio. More specifically, the mechanical properties of CNT origamis can be tuned and programmed by altering the folding width and topological parameters of Miura-ori patterns. Our findings provide new opportunities for the realization of low-dimensional architected nanomaterials capable of achieving tunable mechanical properties and auxeticity.