Portuguese 
English 
Spanish 
7 min of reading 
0 comments 
After almost 40 years in storage, the three-sided zipper created by William Freeman gained a new version at MIT, made with 3D printing, capable of transforming flexible objects into rigid structures and facilitating the assembly of tents, medical splints, robots, and rescue equipment.
After almost 40 years in storage since William Freeman’s first patent, the three-sided zipper has returned to the center of an MIT project with a 3D-printed version, capable of transforming flexible structures into rigid ones and facilitating the assembly of tents, bags, medical equipment, robots, and artistic installations.
The new approach was developed by researchers at MIT’s Computer Science and Artificial Intelligence Laboratory, CSAIL, based on an idea presented in 1985 to the Innovative Design Fund. At the time, the fund published an advertisement in Scientific American offering up to US$10,000 to support smart prototypes for clothing, decor, and textiles.
William Freeman, PhD, then an electrical engineer at Polaroid and now an MIT professor, responded to the advertisement with a project different from the conventional zipper. Instead of merely closing pants or jackets, the mechanism would function as a switch between rigid and flexible states.
-
In just 3 years, India transformed a dry and rocky area into the world’s largest “green battery,” with two artificial lakes that make the water rise and fall to store solar and wind energy as if the entire terrain became a natural battery.
-
Brazil injects R$ 800 million into phase 2 of Sirius, the largest scientific machine ever built in the country, a particle accelerator that uses light to see inside materials and boost energy, health, and technology.
-
China tows a 24,100-ton floating “wind island” out to sea, secures the structure with 9 giant anchors, and erects a 270-meter turbine to withstand 20-meter waves 70 km off the coast.
-
China launched new satellites to test technology that can bring internet directly to mobile phones, without a tower in the way: the Long March-2D rocket took off from Xichang, in Sichuan, with the mission to validate satellite-to-phone broadband.
The proposal targeted objects like chairs, tents, and bags, which could be transported more easily and assembled more simply. The concept was rejected, but Freeman patented the prototype and kept it stored in his garage, with the expectation that it might be useful in the future.
Three-sided zipper born as an alternative for foldable structures
Freeman’s original design resembled a common zipper but with a triangular shape. On each side, there was a strip used to connect narrow wooden teeth, creating a structure that could be locked by a slider encompassing the entire device.
When this slider was moved upwards, the three strips were held in place, straightened, and formed a triangular tube. The idea allowed an object to transition from a flexible configuration to a rigid structure more quickly and reversibly.
Decades later, CSAIL researchers decided to revive the concept to create items with adjustable rigidity. The goal was to overcome limitations of previous attempts, which were not easily reversible or required manual assembly to change the shape of objects.
The team developed an automated design tool and an adaptable fastener called the “Y-zipper.” The system allows for customizing three-sided zipper models and automatically producing them on a 3D printer using plastic.
These devices can be attached to existing objects or incorporated into new products. Tested or foreseen applications include camping equipment, medical devices, robots, and artistic installations that need to alternate between flexibility and rigidity.
Jiaji Li, an MIT postdoctoral researcher, CSAIL researcher, and one of the main authors of the open-access paper on the project, states that a common zipper is efficient for closing flat objects, such as jackets. Freeman’s envisioned mechanism, however, paves the way for transforming more complex items with current manufacturing technology.
Software allows zipper customization before 3D printing
In the software developed by CSAIL, users can define how the fastener will look when closed. Customization includes the length of each strip, as well as the direction and angle of curvature.
The tool also offers four motion primitives to determine the appearance of the closed zipper. The options are straight, curved, spiral, and twisted, each with a different visual and structural behavior.
The straight shape creates a structure more like a rod. The curved resembles an arch, the spiral approaches a spring, and the twisted presents an appearance similar to screws.
The Y-zipper changes shape in the real world as it is opened or closed. When open, it can resemble a squid with three spread tentacles; when closed, it becomes a more compact and resistant structure.
This transition is one of the project’s main features. The team developed a process to build objects that can be quickly transformed from flexible to rigid, with functionality foreseen for real-world use situations.
The paper presenting the project was published in the Proceedings of the 2026 CHI Conference on Human Factors in Computing Systems. The publication describes the creation of the mechanism, the design software, and the tests conducted to evaluate resistance, flexibility, and durability.
Tent assembly can drop from six minutes to one minute and 20 seconds
One of the applications demonstrated by CSAIL involves camping equipment. Setting up a tent by one person can take up to six minutes, but with the Y-zipper, the process can be reduced to one minute and 20 seconds.
In this example, each arm of the device is attached to one side of the tent. The system supports the structure from above and locks the cover into place as the zipper is closed.
The advantage lies in the rapid transition between the flexible state, used for transport, and the rigid state, necessary to keep the object assembled. The same logic can be applied to other items that need to combine ease of movement with structural firmness.
The team also explored the use of the Y-zipper in wearable devices for medical scenarios. The mechanism was wrapped around a wrist splint, allowing the user to loosen it during the day and close it at night.
This alternation helps make the device more comfortable without eliminating its protective function. At night, the structure can be closed to prevent further injuries; during the day, it can be adjusted to reduce discomfort.
The proposal shows how an apparently rigid object can adapt to the patient’s needs. The same principle of adjustable rigidity can expand the use of medical equipment that requires support but also needs to allow for comfort and mobility.
Y-zipper can move robots and create dynamic installations
The system can also be used in motor-driven technologies. After manufacturing, a motor can be attached to the Y-zipper to automate closing and pave the way for objects that change shape at the touch of a button.
Among the examples is an adaptable quadruped robot. The robot could alter the size of its legs, shrinking them to form taller limbs or unzipping when it needed to be closer to the ground.
These quick adjustments could help robots explore uneven terrain. The material cites environments such as canyons and forests, where changes in height and posture can be useful for traversing obstacles.
Another application involves dynamic art installations. The team created a long, winding flower that bloomed by means of a static motor responsible for closing the device with the zipper.
In this case, the mechanism functions as part of the work itself. The movement does not depend on constant manual assembly, as the motor drives the transition between shapes.
The combination of digital fabrication, adjustable rigidity, and motorized actuation expands the use of the Y-zipper for objects that need to transform repeatedly. The proposal unites design, robotics, and flexible structures in a single system.
Tests measured strength, flexibility, and durability
Despite the creative potential, researchers still needed to understand if the Y-zipper would withstand daily use. To do this, the team conducted a series of strength tests with materials used in 3D printing.
Scientists evaluated polylactic acid, known as PLA, and thermoplastic polyurethane, called TPU. Both are common plastics in 3D printers but showed different behaviors in the experiments.
With a machine that bent the Y-zippers, researchers identified that PLA supported heavier loads. TPU, on the other hand, showed greater malleability, an important characteristic for applications requiring more flexibility.
In another test, an actuator continuously opened and closed the Y-zipper. The goal was to measure how long the mechanism would take to break under intense repetitive use.
The device broke after about 18,000 opening and closing cycles. 3D simulations indicated that the system’s durability is linked to its elastic structure, capable of distributing the tension caused by heavy loads.
Even with these results, Li envisions an even more resistant version of the three-sided zipper. The use of materials like metal appears as a possibility to increase durability in more demanding applications.
Next versions can scale up and reach new uses
The team also sees room to expand the size of Y-zippers in larger-scale projects. This expansion, however, still faces a limitation in the current 3D printing platform.
Some applications remain unexplored. Among them is space exploration, where the Y-zipper’s tentacles could be integrated into a spacecraft to collect samples from nearby rocks.
The system could also be incorporated into rapid assembly structures. In natural disasters and rescue operations, such zippers could help teams set up shelters or medical tents more quickly.
Guanyun Wang, an assistant professor at Zhejiang University who was not involved in the study, evaluated the proposal as a way to reimagine a common zipper to handle 3D morphological transitions. The researcher also highlighted the mechanism’s ability to reduce the distance between flexible and rigid states.
For Wang, the approach offers a scalable and innovative manufacturing path for the future of embodied intelligence design. Almost four decades after Freeman’s patent, the three-sided zipper ceases to be a stored prototype and becomes part of a new generation of adjustable structures.
Be the first to react!