In
1985, the Innovative Design Fund placed an ad in Scientific American offering
up to $10,000 to support clever prototypes for clothing, home decor, and
textiles. William Freeman Ph.D., then an electrical engineer at Polaroid and
now an MIT professor, saw it and submitted a novel idea: a three-sided zipper.
Instead of fastening pants, it'd be like a switch that seamlessly flipped
chairs, tents, and purses between soft and rigid states, making them easier to
pack and put together.
Freeman's blueprint was much like a
regular zipper, except triangular. On each side, he nailed a belt to connect
narrow wooden "teeth" together. A slider wrapping around the device
could be moved up to fasten the three strips into place, straightening them
into a triangular tube. His proposal was rejected, but Freeman patented his
prototype and stored it in his garage in the hopes it might come in handy one
day.
Nearly 40 years later, MIT Computer
Science and Artificial Intelligence Laboratory (CSAIL) researchers wanted to
revive the project to create items with "tunable stiffness." Prior
attempts to adjust that weren't easily reversible or required manual assembly,
so CSAIL built an automated design tool and adaptable fastener called the
"Y-zipper." The scientists' software program helps users customize
three-sided zippers, which it then builds on its own in a 3D printer using
plastics. These devices can be attached or embedded into camping equipment,
medical gear, robots, and art installations for more convenient assembly.
"A regular zipper is great for
closing up flat objects, like a jacket, but Freeman ideated something more
dynamic. Using current fabrication technology, his mechanism can transform more
complex items," says MIT postdoc and CSAIL researcher Jiaji Li, who is a
lead author on an open-access paper presenting the project. "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."
The paper is published in the journal Proceedings of the 2026 CHI Conference on Human Factors in Computing Systems.
Credit: Jiaji Li
Why zippers?
Users can customize how the
fasteners look when they're zipped up in CSAIL's software program; they can
select the length of each strip, as well as the direction and angle at which
they'll bend. They can also choose from one of four motion "primitives"
to select how the zipper will appear when it's zipped up: straight, bent
(similar to an arch), coiled (resembling a spring), or twisted (looks like
screws).
The Y-zipper that results will
appear to shape-shift in the real world. When unzipped, it can look like a
squid with three sprawling tentacles, and when you close it up, it becomes a
more compact structure (like a rod, for instance). This flexibility could be
useful when you're traveling—take pitching a tent, for example. The process can
take up to six minutes to do alone, but with the Y-zipper's help, it can be
done in one minute and 20 seconds. You simply attach each arm to a side of the
tent, supporting the structure from the top so that the zipper seemingly pops
the canopy into place.
This seamless transition could also
unlock more flexible wearables, often useful in medical scenarios. The team
wrapped the Y-zipper around a wrist cast, so that a user could loosen it during
the day, and zip it up at night to prevent further injuries. In turn, a
seemingly stiff device can be made more comfortable, adjusting to a patient's
needs.
The system can also aid users in
crafting technology that moves at the push of a button. One can attach a motor
to the Y-zipper after fabrication to automate the zipping process, which helps
build things like an adaptive robotic quadruped. The robot could potentially
change the size of its legs, tightening up into taller limbs and unzipping when
it needs to be lower to the ground. Eventually, such rapid adjustments could
help the robot explore the uneven terrain of places like canyons or forests.
Actuated Y-zippers can also build
dynamic art installations—for example, the team created a long, winding flower
that "bloomed" thanks to a static motor zipping up the device.
Mastering the material
While Li and his colleagues saw the
creative potential of the Y-zipper, it wasn't yet clear how durable it would
be. Could they sustain daily use?
The team ran a series of stress
tests to find out. First, they evaluated the strength and flexibility of
polylactic acid (PLA) and thermoplastic polyurethane (TPU), two plastics
commonly used in 3D printing. Using a machine that bent the Y-zippers down, they
found that PLA could handle heavier loads, while TPU was more pliable.
In another experiment, CSAIL
researchers used an actuator to continuously open and close the Y-zipper to see
how long it'd take to snap. Some 18,000 cycles of zipping and unzipping later,
they finally broke. Y-zipper's secret to durability, according to 3D
simulations, is its elastic structure, which helps distribute the stress of
heavy loads.
Despite these findings, Li
envisions an even more durable three-sided zipper using stronger materials,
like metal. The team may also make the zippers bigger for larger-scale
projects, but that's not yet possible with their current 3D printing platform.
Jiaji also notes that some
applications remain unexplored, like space exploration, wherein Y-zipper's
tentacles could be built into a spacecraft to grab nearby rock samples.
Likewise, the zippers could be embedded into structures that can be assembled
rapidly, helping relief workers quickly set up shelters or medical tents during
natural disasters and rescues.
"Reimagining an everyday
zipper to tackle 3D morphological transitions is a brilliant approach to
dynamic assembly," says Zhejiang University assistant professor Guanyun
Wang, who wasn't involved in the paper. "More importantly, it effectively
bridges the gap between soft and rigid states, offering a highly scalable and
innovative fabrication approach that will greatly benefit the future design of
embodied intelligence."
The researchers' work was presented at the ACM's Computer-Human Interaction (CHI) conference on Human Factors in Computing Systems in April.
Source: After a 40-year wait, technology finally enables three-sided zipper design
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