The design and fabrication of hierarchical multi-stable structures using multi-material Additive Manufacturing (AM) is presented. First a reversible bistable unit actuator is designed to serve as the basis of the design hierarchy. With this unit actuator, the authors present monolithically printed proof-of-concept structures that can transform to multiple activated states, all of which are stable without the need for continuous energy input. The equilibrium positions of these hierarchical designs are found through iterative form finding when necessary. The novel structures illustrated in this paper are only made possible through design for AM that exploits the capabilities of a multi-material, inkjet 3D printer. The design procedure is illustrated through two concepts. The first consists of a series of tetrahedra fabricated as tiled deployable triangles with the out-of-plane members consisting of the actuators in the retracted configuration. The second concept consists of multiple shape changing square unit modules tiled in a grid to achieve complex 3D activated states including a hemisphere, a hyperbolic paraboloid, a star and a cube. Their design and prototyping form the foundation for new types of active and deployable 3D printed structures.
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