Preprogramming Functional Behaviors of Thin Hemispherical Shells via Engineered Defects

The high sensitivity of thin shell buckling with respect to structural imperfections is a well-known issue resulting in deviations between theoretical and experimental findings. These imperfections often arise from unwanted manufacturing defects. In this work, we investigate the effects of seeding strategic macro scale imperfections in soft, thin hemispherical shells to achieve multifunctional and preprogrammable behaviors. A variety of seeded imperfections, including narrow, symmetry-breaking channels or fixed ridges, are explored to enable the activation of different buckling modes, thereby unlocking complex reconfigurable deformation patterns. We explore analytical, numerical, and experimental formulations to inform the placement of seeded imperfections and highlight agreement across each model. We demonstrate that pneumatically-actuated soft hemispherical shells with seeded imperfections can be leveraged to grasp delicate objects through selected contact points. This approach creates new pathways to harness the post-buckling behavior of thin shells within the design of next-generation intelligent devices.