Deformation response of highly stretchable and ductile graphene kirigami under uniaxial and biaxial tension

Kirigami, the ancient technique of paper cutting, has been successfully applied to enhance the stretchability and ductility of nanoscale graphene. However, existing experimentally realized graphene kirigami (GK) are created by introducing parallel cuts, exhibiting exceptional mechanical properties in the direction perpendicular to the cuts but brittleness in the other direction. To overcome this limitation, we propose a fractal-cut GK with rotating triangular units, enabling high stretchability and ductility in both planar directions. We investigate the deformation response of this GK under uniaxial and biaxial tension using classic molecular dynamics simulations. The results demonstrate significant improvements compared with pristine graphene, with yield and fracture strains increased by more than 3 and 5 times, respectively, under uniaxial tension and by more than 3 and 4 times, respectively, under biaxial tension. Detailed analysis shows that high stretchability is attributed to the deformation mechanism of incision rotation and flipping, while high ductility is due to the deformation mechanism of incision rotation accompanied by ligament tearing. This configured GK is expected to open avenues into the design of flexible electronic devices at the nanoscale.