MIT revives 1985 zipper patent with 3D-printed Y-zipper that stiffens on demand

Researchers at MIT CSAIL have developed Y-zipper, a 3D-printed three-sided fastening system that transitions between flexible and rigid states via a single sliding motion. The project revives a 1985 patent by MIT professor William Freeman, which was unrealized due to fabrication limitations. The Y-zipper interlocks three flexible strips into a rigid triangular tube; when unzipped, it behaves like a bundle of ribbons. A digital design tool allows users to generate custom geometries using motion primitives like straight, bend, coil, and screw. The mechanism is fabricated from PLA and TPU as flat strips that self-assemble when zipped. Applications include a wearable wrist brace for TFCC rehabilitation, an adaptive quadruped robot with extendable legs, and a tent with 1.5-meter zipper poles that can be erected by one person in 80 seconds. The team also developed motorized actuation for autonomous assembly. Durability tests showed the zipper withstood over 18,000 open-close cycles before failure. The research is available online.