CSAIL’s three-sided zipper: 3D-printed fasteners for tents and

CSAIL researchers led by associate professor Stefanie Mueller have rebuilt a three-sided zipper into an adaptable fastener that can be designed in software and 3D-printed in plastic. The system, inspired by a mid-1980s patent from William Freeman, produces three flexible arms that zip together to form objects that switch from flexible to rigid.

What is the three-sided zipper and where did it come from?

The three-sided zipper is a fastener with three interlocking, flexible arms that can form different rigid shapes when zipped together. The team credits an abandoned prototype and a patent filed in the mid-1980s by William Freeman, PhD ’92, now an MIT professor, as the original idea they reworked into a configurable system.

How can people design and print these fasteners?

Users use software developed by the CSAIL team to customize strip length, and the direction and angle at which the strips will bend, then 3D-print the parts in plastic. The software also lets users choose whether the zipped device will appear straight, bent, coiled, or twisted, producing parts tailored to the intended geometry.

What can the zipper do in practice?

The researchers demonstrated applications across camping, medical devices and robotics: a tent that uses the zipper can be set up in 80 seconds, a wrist cast incorporating the fastener can be tightened and loosened as desired, and a motor can be added so a robot’s leg heights could change with the push of a button. The paper presenting the project lists these examples to show the fastener’s range of use.

Who built the project and what do they say?

The work was led by associate professor Stefanie Mueller at CSAIL, with MIT postdoc Jiaji Li as a lead author on the paper presenting the project. "A regular zipper is great for closing up flat objects, like a jacket, but Freeman ideated something more dynamic," Li says. She adds, "We’ve developed a process that builds objects you can rapidly shift from flexible to rigid, and you can be confident they’ll work in the real world."

Why it matters

The design turns a familiar fastening concept into a configurable structural element, letting the same basic mechanism serve quick-deploy consumer gear, adjustable medical supports and reconfigurable robot parts. That narrows the gap between digital design and physical behavior: users choose geometry in software, print in plastic, and get parts that change stiffness through the zipper action.

What to watch

Look for the CSAIL team’s paper and follow-up demos showing durability and load-bearing limits for larger structures, and for examples of motorized assemblies that exploit the zipper to change shape under control.