In 1985, the Novel Design Fund placed announcement offering up to $10,000 to support imaginative prototypes of clothing, home furnishings and textiles. Dr. William Freeman ’92, then an electrical engineer at Polaroid and now a professor at MIT, saw this and came up with a novel idea: the three-way zipper. Instead of zipping up your pants, it would be like a switch that seamlessly switches chairs, tents, and handbags between pliable and stiff states, making them easier to pack and fold.
Freeman’s design was very similar to a regular zipper, except that it was triangular. He nailed a strip on both sides to connect the narrow wooden “teeth” together. The slider surrounding the device can be moved up to secure the three straps in place, straightening them into a triangular tube. His proposal was rejected, but Freeman patented his prototype and kept it in his garage in the hope that it might come in handy one day.
Nearly 40 years later, researchers at the MIT Computer Science and Artificial Intelligence Laboratory (CSAIL) wanted to revive the project to create objects with “adjustable stiffness.” Previous attempts at adjustments that were not easily reversible or required manual installation, so CSAIL created an automated design tool and an adaptable fastener called the “Y-lock”. The software developed by the researchers helps users customize three-way zippers, which they then build themselves on a 3D printer using plastics. These devices can be attached or embedded in camping equipment, medical equipment, robots and art installations for more convenient installation.
“A regular zipper is great for fastening flat items like a jacket, but Freeman came up with an idea for something more dynamic. Using current manufacturing technology, its mechanism can transform more complex items,” says Jiaji Li, a researcher at MIT and CSAIL, lead author of an open-access paper introducing the project. “We have developed a process to create objects that can be quickly changed from flexible to rigid and you can be sure they will work in the real world.”
Y-lock: 3D printing pliant and unyielding transitions with one click
Why zippers?
Users can customize the appearance of fasteners when fastened in CSAIL software; they can choose the length of each strip, as well as the direction and angle at which they will bend. They can also select one of four movement “primitives” to choose how the zipper will look when it is closed: straight, bent (like a bow), coiled (like a spring), or twisted (looks like screws).
The resulting Y-lock will appear to “shape-shift” in the real world. When unzipped, it may look like a squid with three spreading tentacles, and when closed, it becomes a more compact structure (like a rod, for example). This flexibility can be useful when traveling – for example, when pitching a tent. The process itself can take up to six minutes, but with a Y-lock it can be done in one minute and 20 seconds. Simply attach each arm to the side of the tent, supporting the structure from above so that the zipper seemingly slides the canopy into place.
This silky transition could also enable more pliant wearable devices, often useful in medical applications. The team wrapped a Y-lock around the wrist cast so the user could loosen it during the day and tighten it at night to prevent further injury. In turn, a seemingly unyielding device can be made more comfortable by adapting to the patient’s needs.
The system can also aid users create technology that works at the touch of a button. Once manufactured, a motor can be attached to the Y-lock to automate the fastening process, helping to build things like an adaptive robotic quadruped. The robot could potentially change the size of its legs, tapering into taller limbs and unzipping when it needed to lower them lower to the ground. Ultimately, such quick adjustments could aid the robot explore the rugged terrain of places such as canyons and forests. Actuated Y-locks can also be used to create energetic art installations – for example, the team created a long, winding flower that “bloomed” thanks to a unchanging motor zipping the device.
Mastering the material
Although Li and his colleagues saw the artistic potential of the Y-lock, it was not yet clear how hard-wearing it would be. Will they withstand everyday exploit?
Li and Freeman wrote the paper with Tianjin University doctoral student Xiang Chang and MIT CSAIL colleagues: doctoral student Maxine Perroni-Scharf; undergraduate student Dingning Cao; recent visiting researchers Mingming Li (Zhejiang University), Jeremy Mrzyglocki (Technical University of Munich), and Takumi Yamamoto (Keio University); and MIT Associate Professor Stefanie Mueller, who is CSAIL’s principal investigator and lead author of this paper. Their research was supported in part by a postdoctoral fellowship at Zhejiang University and the MIT-GIST program.
The researchers’ work was presented in April at the ACM Human Factors in Computing Systems (CHI) Conference on Human Factors in Computing Systems.