Bistable structures that can switch between two stable shapes are ubiquitous and have found applications in deployable structures, actuators, energy harvesters, etc. Among these, a bistable, spherical shell can stay stable in either the natural or “everted” shape. Previous works concentrate on the bistability of an intact shell, yet few efforts have been put into shells that feature a toy popper – a spherical shell with a circular hole located at its apex. To expand the existing design space of bistable shells, it is necessary to identify the quantitative relationship between the shell’s bistability and the size of this geometric and topological defect. In this paper, through experiments, theory, and finite element analysis (FEA), we demonstrate that the bistability of a popper-like shell is mainly controlled by its geometric parameters and gets weakened initially and then enhanced as the relative size of the defect increases, indicating that a properly introduced defect can shift an intact shell from bistability to monostability or vice versa. Therefore, our research not only identifies the enriched design space of bistable shells, but also may advance the development of intelligent structures and devices such as smart switches and soft robotics, where the bistable shells can be employed.

可以在两个稳定形状之间切换的双稳态结构无处不在，并且已经在可展开结构，致动器，能量收集器等中得到了应用。在这些结构中，双稳态球形壳体可以保持自然或“外翻”形状的稳定性。先前的工作着重于完整外壳的双稳性，但很少有人为具有玩具弹夹的外壳做任何努力-球形外壳的顶部带有一个圆形孔。为了扩展现有的双稳态壳体设计空间，有必要确定壳体的双稳性与该几何和拓扑缺陷的大小之间的定量关系。本文通过实验，理论和有限元分析（FEA），我们证明了类似波普尔壳的双稳性主要受其几何参数控制，并随着缺陷的相对尺寸增加而先减弱然后增强，这表明适当引入的缺陷可使完整的壳从双稳性转变为单稳性或反之亦然。因此，我们的研究不仅确定了双稳态壳体的丰富设计空间，而且还可以促进可以使用双稳态壳体的智能结构和设备的开发，例如智能开关和软机器人。