Common push puppet toys, often shaped like animals or popular characters, can move or collapse with a simple button press at the bottom of their base. Recently, a group of engineers from UCLA has developed a new type of tunable dynamic material that replicates how push puppets operate. This innovation has potential applications in soft robotics, adaptable architecture, and space engineering.
Common push puppet toys in the shapes of animals and popular figures can move or collapse with the push of a button at the bottom of the toys’ base. Now, a team of UCLA engineers has created a new class of tunable dynamic material that mimics the inner workings of push puppets, with applications for soft robotics, reconfigurable architectures and space engineering.
Within a push puppet, there are cords that, when tightened, keep the toy upright. When these cords are loosened, the puppet’s “limbs” become floppy. By applying this cord tension mechanism, researchers have come up with an innovative type of metamaterial—specialized materials designed to have unique capabilities.
According to a study published in Materials Horizons, this new lightweight metamaterial features motor-driven or self-activating cords that are threaded through interlocking cone-tipped beads. When these cords are activated, they tighten, causing the bead chain to jam and align in a straight line, which makes the material rigid while keeping its overall shape intact.
The research also highlighted this material’s adaptable properties, which could enable its use in soft robotics and other reconfigurable structures:
- The cord tension allows for “tuning” the stiffness of the material. When the cords are completely taut, the structure is at its strongest, but slight adjustments in tension can allow the material to bend while still being robust. This adaptability is due to the precise shape of the nesting cones and their friction.
- Structures made with this design can repeatedly collapse and stiffen, making them ideal for long-term use in designs requiring continuous movement. Additionally, the material is easier to transport and store in its flaccid, undeployed state.
- Post-deployment, the material shows remarkable adjustability, becoming over 35 times stiffer and altering its damping properties by 50%.
- This metamaterial could also be created to trigger its own activation, utilizing artificial tendons to change shape without needing human intervention.
“Our metamaterial opens up new possibilities, showcasing its potential for use in robotics, flexible structures, and space technology,” explained Wenzhong Yan, the corresponding author and a postdoctoral scholar at UCLA’s Samueli School of Engineering. “A self-deployable soft robot utilizing this material could adapt its limb stiffness for varying terrains, enhancing its movement while maintaining its overall shape. Additionally, a sturdy metamaterial could assist a robot in lifting, pushing, or pulling objects.”
“The concept of contracting-cord metamaterials paves the way for fascinating advancements in integrating mechanical intelligence into robots and other devices,” Yan added.
A brief 12-second video showcasing the metamaterial is accessible here, via the UCLA Samueli YouTube Channel.
The senior authors of the study include Ankur Mehta, an associate professor of electrical and computer engineering at UCLA and director of the Laboratory for Embedded Machines and Ubiquitous Robots, with Yan being a team member, and Jonathan Hopkins, a professor of mechanical and aerospace engineering who heads UCLA’s Flexible Research Group.
The research team believes potential uses for this material could extend to self-assembling shelters featuring shells that contain collapsible scaffolding, as well as compact shock absorbers with programmable damping for vehicles navigating rough terrain.
“In the future, there is significant potential to explore customization and capability enhancement by modifying the size and shape of the beads and their connections,” Mehta stated, who also holds a faculty position in mechanical and aerospace engineering at UCLA.
While previous studies have looked into contracting cords, this research has focused on the mechanical attributes of the system, such as optimal bead shapes for alignment, self-assembly, and their ability to maintain structural integrity.
Other contributors to the study include graduate students Talmage Jones and Ryan Lee from UCLA’s mechanical engineering program, who are part of Hopkins’ lab, and Christopher Jawetz, a Georgia Institute of Technology graduate who contributed to the research during his undergraduate studies in aerospace engineering at UCLA.
This research was supported by the Office of Naval Research and the Defense Advanced Research Projects Agency, with additional backing from the Air Force Office of Scientific Research and resources from UCLA’s Office of Advanced Research Computing.
