A deployable structure can transition from a compact state to an expanded one. Such structures usually require rather complicated locking mechanisms to hold them in place. Today’s deployable structures aren’t always reliable or autonomous. Harnessing the domino effect, researchers have designed deployable systems that expand quickly with a small push and are stable and locked into place after deployment.
Multi-stable structures are being used in a range of applications including recon-figurable architectures, medical devices, soft robots, and deployable solar panels for aerospace. Usually, to deploy these structures, a complicated actuation process is needed; however, the simple domino effect is used in this work to create a reliable deployment process.
Mechanically speaking, a domino effect occurs when a multi-stable building block (the domino) switches from its high-energy state (standing) to its low-energy state (laying down) in response to an external stimulus like the push of a finger. When the first domino is toppled, it transfers its energy to its neighbor, initiating a wave that sequentially switches all building blocks from high- to low-energy states.
The researchers focused on a simple system of bistable joints linked by rigid bars. They first showed that by carefully designing the connections between the links, transition waves could propagate through the entire structure — transforming the initial straight configuration to a curved one. Then, using these building blocks, they designed a deployable dome that could pop up from flat with one small push.
Being able to predict and program this kind of highly nonlinear behavior opens up many opportunities and has the potential not only for morphing surfaces and reconfigurable devices but also for propulsion in soft robotics, mechanical logic, and controlled energy absorption. The team is also working on understanding and controlling transition waves in two-dimensional mechanical metamaterials and has already demonstrated a 2D system in which they can control the direction, shape, and velocity of transition waves by changing the shape or stiffness of the building blocks and incorporating defects into the materials. The researchers designed materials wherein the waves moved horizontally, vertically, diagonally, circularly, and even wiggled back and forth like a snake.