The role of geometry in the rapid snap-through of hummingbird beak-inspired morphing structures

Achieving efficient, high-speed, and controllable actuation remains a central challenge in soft robotics. Nature serves as a rich source of inspiration for addressing this bottleneck. This paper investigates the influence of geometric morphology on the snap-through behaviour of a soft-robotic end-effector inspired by the hummingbird beak–a biological system highly evolved for rapid closure driven by instability. We aim to elucidate the mechanical principles governing this swift shape-shifting response to guide the design of bio-inspired, fast-response robots. We develop a parametric finite element model of the beak-inspired structure using beam elements in the commercial finite element package Abaqus. The model simulates the beak-inspired structure’s nonlinear response under actuation inputs. We focus on the strain energy released during the snap-through instability, a key quantity influencing the rapid movement of the beak-inspired structure. Parametric studies explore the effects of beak geometry, including both its beam axis and cross-sectional properties. To gain insight into how geometric parameters affect behaviour, we develop a post-processing script to unveil how local strain energy variations contribute to the overall energy release. Furthermore, we conduct a structural optimisation of the beak-inspired structure’s geometry, considering both its beam axis and cross-sectional properties. The resulting optimised shape confirms the trends observed in the parametric studies and correlates strongly with the morphology of the hummingbird beak as shown by computed tomography scans found in the literature—the latter having been optimised for performance through natural selection. Drawing inspiration from the hummingbird beak, this work underscores the role of geometric design as a means to achieve rapid movement in soft robotic systems through nonlinear mechanics. A clear understanding of this relationship is thus vital to elucidate the mechanical principles governing snap-through motion and to unlock its potential for biomimetic applications in soft robotics–a field where efficient, high-speed, and controllable actuation is a central objective.