Science in movies is always iffy, but that doesn’t stop it from inspiring real-world scientists. Duke’s Mohamed Noor teaches biology courses based on “Star Trek,” while Cold Spring Harbor’s Aspyn Palatnick developed his own genetic analyzer reminiscent of the movie’s infamous tricorder. And when Michigan State University entomologists discovered more than 3 dozen new species of ambrosia beetles, they knew just who to name them after—iconic female science fiction characters.
In new research, engineers at NTU Singapore and CalTech have added to the list of movie-inspired creations, designing a new type of 3D-printed chain mail fabric that is generally flexible but can stiffen on demand, like Christian Bale’s gliding cape in “Batman Begins.”
The innovation could pave the way for next-generation smart fabrics that can harden to protect a user against an impact or when additional load-bearing capacity is needed, including bullet- and stab-proof vests, medical support systems for the elderly and even protective exoskeletons for sports or construction sites.
The principle behind the nylon fabric is called “jamming transition,” in which aggregates of solid particles switch from a fluid-like soft state to a solid-like rigid state with a slight increase in packing density. What the scientists determined in their most recent research, published in Nature, is that the shape of the particle plays a role.
The authors designed and printed numerous structured particles as hollow octahedrons—a shape with eight equal triangular faces—in the form of rings, ovals, squares, cubes and pyramids. They then modeled how much each structure would bend in response to the amount of applied stress. The results indicated to the team that, by customizing the particle shape, there’s a trade-off between how much weight the particles will have versus how much the fabric can bend—and how to balance the two factors.
To control the stiffness of the fabric, the researchers wrapped the fabric in a flexible plastic envelope vacuum-packed it.
“The vacuum pressure increased the packing density of the fabric, causing each particle to have more contact with its neighbors, resulting, for the octahedron-based fabric, in a structure that is 25 times more rigid,” explains the research team.
For example, the team dropped a 30-gram steel ball onto the fabric at 3 meters per second. When relaxed, the fabric deformed by 26 mm; but when stiffened, the impact deformed the fabric by only 3 mm. In another experiment that formed the fabric into a flat structure, the team demonstrated that it could hold more than 50x its own weight once vacuum-packed.
While the scientists initially started working with nylon fabric, they have already begun testing other source material. When they 3D-printed the material using aluminum, it demonstrated the same flexibility when soft as nylon, but was much stiffer when rigid due to aluminum’s higher strength.
First author Wang Yifan, an associate professor at NTU, said the aluminum-derived materials could be used in the future for larger-scale industrial applications requiring higher load capacity, such as bridges or buildings.
Beyond source material, Yifan said the research team is also exploring additional methods of stiffening the octahedrons, such as through magnetism, electricity or temperature.
Photo: When stiffened, the new chain mail fabric developed by the research team can withstand up to 50 times its own weight. Credit: NTU Singapore and CalTech