The algorithm uses a two-step method to find the optimal path through the tile pattern for a string that can be tightened to actuate the structure. It computes the minimum number of points that the string must lift to create the desired shape and finds the shortest path that connects those lift points, while including all areas of the object’s boundary that must be connected to guide the structure into its 3D configuration. It does these calculations in such a way that the string path minimizes friction, enabling the structure to be smoothly actuated with just one pull.

The actuation method is easily reversible to return the structure to its flat configuration. The patterns could be produced using 3D printing, CNC milling, molding, or other techniques.

This method could enable complex 3D structures to be stored and transported more efficiently and with less cost. Applications could include transportable medical devices, foldable robots that can flatten to enter hard-to-reach spaces, or even modular space habitats deployed by robots on the surface of Mars.

“The simplicity of the whole actuation mechanism is a real benefit of our approach,” says Akib Zaman, a graduate student in electrical engineering and computer science and lead author of a paper on the work. “The user just needs to provide their intended design, and then our method optimizes it in such a way that it holds the shape after just one pull on the string, so the structure can be deployed very easily. I hope people will be able to use this method to create a wide variety of different, deployable structures.” 

The researchers used their method to design several objects of different sizes, from personalized medical items including a splint and a posture corrector to an igloo-like portable structure. They also designed and fabricated a human-scale chair. The technique could be used to create items ranging in size from tiny objects actuated inside the body to architectural structures, like the frame of a building, that are deployed on-site using cranes.

In the future, the researchers want to further explore designs at both ends of that range. In addition, they want to create a self-deploying mechanism, so the structures do not need to be actuated by a human or robot.