MIT Researchers Create Flat Structures That Transform Into Complex 3D Forms With a Single Pull of a String

MIT researchers have developed a new computational design method that allows complex three-dimensional structures to be created from flat, tile-based configurations, all actuated by one simple pull of a string. This work introduces a powerful way to design deployable structures that are fast to assemble, easy to transport, and fully reversible—addressing long-standing challenges in architecture, robotics, medical devices, and emergency response systems.

The research, published in ACM Transactions on Graphics (2025), presents an algorithmic system that takes a user-defined 3D shape and automatically converts it into a flat layout made of interconnected tiles. When a string threaded through this flat structure is pulled once, the object smoothly lifts and folds itself into its intended curved 3D form.

From Flat Sheets to Fully Formed 3D Structures

The core idea behind the research is deceptively simple: reduce the complexity of deployment. Traditionally, transforming flat materials into curved or volumetric shapes requires multiple actuators, manual assembly, motors, or irreversible folding steps. In contrast, the MIT team designed a system where a single tensile force—one string—does all the work.

The algorithm begins with a 3D model provided by the user. This model is then decomposed into a grid of quadrilateral tiles, which are connected at their corners using rotational hinges. When laid flat, the structure resembles a flexible sheet. When actuated, the hinges rotate in a coordinated way, allowing the tiles to rise and curve into a stable 3D geometry.

What makes this approach especially notable is that the entire deployment process is reversible. Once the string is released, the structure naturally relaxes and returns to its flat configuration. This reversibility opens the door to repeated deployment and collapse without damaging the structure.

Kirigami, Auxetics, and Geometry-Driven Motion

The researchers drew inspiration from kirigami, the traditional Japanese art of cutting paper to create complex shapes and mechanical behaviors. By carefully designing how the tiles are cut and connected, the team encoded motion directly into the geometry of the structure.

These tile arrangements exhibit auxetic behavior, meaning the structure thickens when stretched and thins when compressed—the opposite of what most materials do. This property is crucial for guiding the transformation from flat to curved forms while maintaining structural stability.

Auxetic mechanisms have been studied for decades in materials science, but integrating them into a fully automated, string-actuated deployment system at arbitrary scales is a significant step forward.

Optimizing the String Path for Minimal Friction

One of the most technically challenging parts of this research was figuring out how to route the string so that the structure deploys smoothly and reliably.

The team developed a two-step optimization process. First, the algorithm determines the minimum number of lift points—specific locations where the string needs to apply force to raise the structure. Second, it calculates the shortest possible path that connects these lift points while also passing through necessary boundary regions of the design.

Crucially, the algorithm minimizes friction along the string path. Too much friction would prevent the structure from deploying evenly or fully. To solve this, the researchers relied on classic physics equations related to friction and tension, adapting them into a computational optimization framework that closely matches real-world behavior.

They also mathematically proved that routing the string through boundary tiles is essential for successful deployment—an insight that emerged from hands-on experimentation with physical prototypes.

Fabrication Without Constraints

Another strength of the system is that it is fabrication-agnostic. The designs generated by the algorithm can be manufactured using a wide range of techniques, including:

• 3D printing
• CNC milling
• Molding
• Hybrid multi-material fabrication

For example, a structure could be 3D printed with flexible materials used for the hinges and rigid materials for the tiles. This flexibility makes the method accessible across industries and scales, from consumer products to architectural installations.

Real-World Prototypes and Demonstrations

To validate their approach, the researchers designed and fabricated multiple working prototypes. These ranged from small medical devices, such as splints and posture correctors, to larger objects like an igloo-shaped portable structure.

One of the most striking demonstrations was a human-scale deployable chair. The chair can be assembled, deployed, collapsed, and transported by a single person, clearly showing how the system could be used for furniture, temporary seating, or mobile infrastructure.

Across all prototypes, the same principle held true: one string, one pull, full deployment.

Why This Matters for Emergency Response and Beyond

The ability to quickly deploy complex structures from flat-packed forms has major implications. In disaster scenarios—such as earthquakes or tsunamis—time is critical. Flat-packed field hospitals or emergency shelters could be transported efficiently and deployed on-site within minutes, without specialized tools or large teams.

Beyond disaster response, the method could support:

• Foldable robots that flatten to move through tight spaces and then expand to perform tasks
• Transportable medical devices designed for low-resource environments
• Space habitats, where robots could deploy structures on Mars or the Moon using minimal energy
• Architectural frameworks that self-deploy on construction sites

Because the system is scale-independent, it can also be adapted for extremely small applications, including deployable devices designed to operate inside the human body.

A Tool Designed for Designers

The researchers integrated their algorithm into an interactive user interface, allowing designers to input a 3D shape and automatically generate a manufacturable, flat deployable version. Users don’t need to manually design hinges, string paths, or actuation mechanisms—the system handles all of it.

This lowers the barrier to entry and enables designers, engineers, and researchers to focus on form and function rather than mechanical complexity.

Broader Context: Deployable Structures in Engineering

Deployable structures have long been used in aerospace engineering, temporary architecture, and robotics. However, most existing systems rely on manual assembly, complex mechanisms, or irreversible folding patterns.

This MIT approach stands out because it combines geometric intelligence, material behavior, and algorithmic optimization into a single, user-friendly pipeline. Instead of adding mechanical complexity, it removes it.

What Comes Next

Looking ahead, the researchers aim to explore self-deploying systems that do not require human or robotic intervention. They also plan to tackle engineering challenges related to hinge durability, string thickness, and structural strength for larger architectural installations.

If successful, this work could redefine how we think about deployable objects—making complex structures as easy to deploy as pulling a drawstring.

Research Paper:
https://doi.org/10.1145/3763357