Assessing the fracture toughness of graphene by in situ AFM mechanical testing

Graphene-related materials exhibit exceptional intrinsic mechanical properties, yet their practical deployment is critically limited by defects that trigger premature failure. Here, we present the first direct coupling of high-resolution Atomic Force Microscopy (AFM) topographic imaging with micro-tensile testing to observe in real-time crack initiation and propagation in monolayer and few-layer graphene produced via mechanical exfoliation on compliant substrates. Artificially introduced nanoscale defects serve as controlled proxies for inevitable imperfections in real-world devices, revealing crack initiation at remarkably low strains − 0.45% in monolayers and 0.62% in few-layer graphene. Quantitative analysis shows that few-layer graphene exhibits a higher fracture toughness (11.0 ± 2.3 MPa·m 1/2 ) than monolayers (7.97 ± 2.10 MPa·m 1/2 ), along with intrinsic mechanisms that impede crack advance. These results establish the first direct in situ quantification of fracture mechanics in supported graphene, bridging atomic-scale defect behaviour with macroscopic reliability. By revealing how nanoscale defects govern failure pathways, this work provides essential design principles for defect-tolerant graphene-based nanodevices and structural materials.