Engineers make tunable, shape-changing metamaterial inspired by vintage toys | Science & Technology

Inside a push puppet, there are connecting cords that, when pulled taught, will make the toy stand stiff. But by loosening these cords, the “limbs” of the toy will go limp. Using the same cord tension-based principle that controls a puppet, researchers have developed a new type of metamaterial, a material engineered to possess properties with promising advanced capabilities.

Published in Materials Horizons, the UCLA study demonstrates the new lightweight metamaterial, which is outfitted with either motor-driven or self-actuating cords that are threaded through interlocking cone-tipped beads. When activated, the cords are pulled tight, causing the nesting chain of bead particles to jam and straighten into a line, making the material turn stiff while maintaining its overall structure.

The study also unveiled the material’s versatile qualities that could lead to its eventual incorporation into soft robotics or other reconfigurable structures:

• The level of tension in the cords can “tune” the resulting structure’s stiffness — a fully taut state offers the strongest and stiffest level, but incremental changes in the cords’ tension allow the structure to flex while still offering strength. The key is the precision geometry of the nesting cones and the friction between them.
• Structures that use the design can collapse and stiffen over and over again, making them useful for long-lasting designs that require repeated movements. The material also offers easier transportation and storage when in its undeployed, limp state.
• After deployment, the material exhibits pronounced tunability, becoming more than…