Bi-shell valve inspired by shell snapping interaction for rapid actuation of soft pneumatic actuators

Delivering rapid motion to a soft pneumatic robot is challenging. So far, existing concepts have relied on the use of either pressure control strategies, chemical explosions embedded into the soft robot body as power source, or structural elements that harness elastic instabilities. In this work, we introduce a bi-shell valve that can offer rapid deflation to soft actuators under volume-controlled conditions and without necessarily need to modify the architecture of the soft robot. The design of the bi-shell valve is inspired by the snapping and interaction of the constituent elastic shells, a hemispherical shell with a large geometric defect and a spherical cap. Upon deflation, the former first stores a sizeable amount of volume change and elastic energy, which are then suddenly released upon the snapping of the latter. By tuning shell geometry and material property, the snapping of the valve can be effectively programmed for target applications. The bi-shell valve along with its two variations for rapid inflation valve and pneumatic volume fuse extends the capabilities of existing strategies to supply fast actuation to soft pneumatic robots.