Elastic instability enabled shape-morphing metamaterials*

The ability to change shape is important for materials in an emerging class of engineering applications including soft robots, which must be able to change shape to adapt to different environments and complete different tasks. Artificial architected structures with the ability to change shape are referred to as shape-morphing metamaterials. Several shape-morphing mechanisms have been proposed in recent years. Among them, elastic instability is one of the promising strategies with efficiency and realizability. Many morphing metamaterials lack the ability to be reprogrammed; we introduce a class of soft morphable metamaterials in which the state of the system can be programmed by exploiting the bistability of an elastic element. The result is a system in which multiple stable shapes can be achieved by reversibly changing the state of individual bistable elements via snap-through, actuated pneumatically. We characterize the operation of such a device, showing how the state of each element can be controlled and that elements may interact if placed close enough together.