MIT revives a 1985 patent into the "Y-zipper," a 3D-printed shape-shifting fastener

In 1985, electrical engineer William Freeman — now an MIT professor — sketched a triangular, three-sided zipper meant to flip objects between soft and rigid states. The idea was rejected by the design fund he pitched, so he patented it and left the wooden prototype in his garage. Nearly four decades later, MIT CSAIL researchers dusted it off and rebuilt it as the “Y-zipper”: a fastener with tunable stiffness, paired with software that lets users specify strip length, bend direction, and one of four motion shapes (straight, bent, coiled, twisted), then auto-generates a 3D-printable design.

The practical hook is reversible assembly. Zipped, a Y-zipper collapses into a compact rod; unzipped, it sprawls into flexible arms. The team used it to pop a tent into shape in under 90 seconds versus roughly six minutes by hand, to build an adjustable wrist cast that loosens by day and stiffens at night, and to drive motorized structures like a quadruped robot that can lengthen or shorten its legs. Durability testing showed the printed parts survived about 18,000 open-close cycles before failing, with PLA handling heavier loads and TPU bending more freely; simulations credit the elastic geometry for spreading stress.

The work, published open-access and presented at ACM CHI in April, is more a fabrication and HCI advance than a security or software story, but it’s a clean example of digital design tools turning a dormant mechanical patent into automated, reconfigurable hardware. The researchers see room to scale up with metal or larger printers, and float uses from disaster-relief shelters to spacecraft sample grabbers.