New 35x stiffer push-puppet-inspired material for self-deployable space robots

Scientists at UCLA Samueli School of Engineering have developed a new lightweight metamaterial that mimics the functionality of push puppets. This material could benefit soft robotics, reconfigurable structures, and space engineering.

“Recent advances,” the study authors state, “in active materials and fabrication techniques have enabled cyclically self-deployable metamaterials with an expanded functionality space.”

However, making a metamaterial that has tunable mechanical properties after self-deployment has posed the field a considerable challenge and the seeds for ingenuity turned out to exist inside a toy.

A children’s toy held the key to ingenuity

Push puppets, often in the shape of animals, are shapeshifters because of internal cords that make the structure collapse or stand up straight. As they demonstrated in a video, the metamaterial retains its shape after breaking down and takes the weight of a ball without falling apart because of the beads that comprise its structure.

As per UCLA , they thread either motor-driven (robotics) or self-actuating cords (like the toy) through the interlocking cone-tipped beads. Similarly to a push puppet, when these cords are tight, this “nesting chain of bead particles” jam together and straighten out into a line.

“The general concept of contracting-cord metamaterials opens up intriguing possibilities on how to build mechanical intelligence into robots and other devices,” corresponding author and UCLA Samueli School of Engineering postdoctoral scholar Wenhong Yan said in an official announcement.

A feat of geometry even, the design hinges upon the shape of the cones and the friction between them. The metamaterial offers a range of stiffness capacities as the cords make the material flexible, also, and it doesn’t lose its strength. For a self-assembling shelter, for example, or scaffolding, the material can continue to be built and broken down for such activities that require reuse. Furthermore, the material can fall flat, which makes it ideal for storage.

After deployment, as this has been the area of difficulty, “the material exhibits pronounced tunability, becoming more than 35 times stiffer and changing its damping capability by 50 percent.” Finally, it can be fully functional without the need of a human hand.

What’s next for the groundbreaking new metamaterial

As Wenhong Yan explained to UCLA, “built with this material , a self-deployable soft robot, for example, could calibrate its limbs’ stiffness to accommodate different terrains for optimal movement while retaining its body structure . The sturdy metamaterial could also help a robot lift, push or pull objects.”

For vehicles, UCLA stated, moving through rough terrain, the metamaterial can absorb shock, which is what “dampening” refers to, and that functionality is programmable.

“Looking ahead, there’s a vast space to explore in tailoring and customizing capabilities by altering the size and shape of the beads, as well as how they are connected,” said Ankur Mehta, a senior author on the paper.

As per UCLA , the Office of Naval Research and the Defense Advanced Research Projects Agency funded this project with additional support from the Air Force Office of Scientific Research, as well as computing and storage services from the UCLA Office of Advanced Research Computing.

The study was published in the journal Materials Horizons .