Switchable Bistability in 3D Printed Shells With Bio-Inspired Architectures and Spatially Distributed Pre-Stress

Using fused deposition modeling (FDM) 3D printing, we combine a bio-inspired bilayer architecture with distributed pre-stress and the shape memory behavior of polylactic acid (PLA) to manufacture shells with switchable bistability. These shells are stiff and monostable at room temperature, but become elastic and bistable with fast morphing when heated above their glass transition temperature. When cooled back down, the shells retain the configuration they were in at the elevated temperature and return to being stiff and monostable. These programmed deformations result from the careful design and control of how the filament is extruded by the printer and therefore, the resulting directional pre-stress. Parameter studies are presented on how to maximize the pre-stress for this application. The shells are analyzed using nonlinear finite element analysis. By leveraging the vast array of geometries accessible with 3D printing, this method can be extended to complex, multi-domain shells, including bio-inspired designs.