Single string pull turns flat designs into 3D structures for modular space habitats

From flat to formed The new method begins with a user-designed 3D shape. An algorithm then converts that shape into a flat layout made of interconnected tiles. Each tile connects through rotating hinges, allowing the structure to fold and unfold without rigid assembly steps. The system calculates how a single string should pass through the structure.

It identifies key lift points and finds the shortest path that minimizes friction. When a user pulls the string, the structure moves smoothly into its final 3D form. If the user releases the string, the structure flattens again. That feature allows repeated deployment without damage or reassembly.

The simplicity of the whole actuation mechanism is a real benefit of our approach. 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, says Akib Zaman, an electrical engineering and computer science graduate student and the paper s lead author.

Inspired by kirigami The researchers drew inspiration from kirigami, the Japanese art of paper cutting. They divided each design into a grid of quadrilateral tiles that behave as an auxetic structure. Auxetic materials grow thicker when stretched and thinner when compressed. This geometry helps the structure move predictably during deployment.

It also allows the string to guide the shape without motors or complex hardware. The team faced a major challenge while modeling friction inside the string channel. Early physical tests revealed that boundary tiles needed closure for reliable deployment. The researchers later proved this behavior mathematically.

They then used a classical physics equation to calculate friction and optimize the string s path. That process ensured smooth motion with minimal force. Our method makes it easy for the user. All they have to do is input their design, and our algorithm automatically takes care of the rest, Zaman says.

The system works at many scales. The researchers tested it on small medical devices, including a splint and a posture corrector. They also built a human-scale chair and an igloo-like portable structure. Because the method does not depend on a specific fabrication process, designers can produce structures using 3D printing, CNC milling, or molding.

Hinges can use flexible materials, while other parts remain rigid. The approach could support foldable robots that flatten to enter tight spaces. It may also help engineers design modular space habitats that robots could deploy on Mars. The research team presented the work at the Association for Computing Machinery s SIGGRAPH Asia conference.

In future studies, they plan to explore self-deploying versions that do not require humans or robots to pull the string. For now, the work points toward a simple idea with broad impact: complex structures do not always need complex assembly. The study is published in the journal ACM Digital Library.