Fracture Mechanics of 2D Crystal Blisters with Irregular Geometry

Abstract Attaching a thin elastic film onto a substrate often traps liquids or gases at the film‐substrate interface, resulting in blisters. While typically undesirable, blisters that spontaneously form during the assembly of atomically thin 2D crystals have demonstrated intriguing functionalities—such as high‐pressure chemistry and liquid‐cell electron microscopy—that exploit the nanoscale confinement of the blister. However, a quantitative understanding of this confinement, including the confining pressure and membrane tension, has been hindered by the irregular shapes of 2D crystal blisters, which occur particularly often in single‐ or few‐layer 2D crystal systems. Here, experiments and theory are combined to reveal how the competition between elastic and adhesive forces in 2D crystal blisters selects the blister shape. It is shown that the geometry of the blister encodes a wealth of useful information, which can be decoded using fracture mechanics concepts, including strain/stress fields, pressure levels, and interface toughness between the 2D crystal and its substrate. These findings have immediate implications for the fabrication and design of 2D crystal‐based devices and applications, where blister formation can be either a hindrance or a beneficial feature.