Push puppet toys, which collapse and stand upright by manipulating internal cords, served as the inspiration for this new material. In these toys, pulling cords tightens them, making the toy stiff, while loosening them causes the limbs to collapse. The UCLA researchers applied this principle to develop a metamaterial that can change its shape and stiffness in a controlled manner.
The metamaterial, detailed in a study published in 'Materials Horizons', is constructed from interlocking cone-tipped beads with cords that are either motor-driven or self-actuating. When the cords are tightened, the beads jam together, causing the material to stiffen while maintaining its structural integrity.
The study highlights the metamaterial's versatility, offering several potential applications:
+ Tunable Stiffness: The stiffness of the material can be adjusted by varying the tension in the cords. When fully tightened, the material becomes extremely rigid, while adjusting the tension allows it to flex while retaining strength. This is achieved through the precise geometry of the nesting cones and the friction between them.
+ Reusability and Storage: The material can repeatedly collapse and stiffen, making it suitable for designs requiring repeated movements. It is also easily stored and transported in its limp, undeployed state.
+ Enhanced Performance: Upon deployment, the material can become more than 35 times stiffer, with a 50% change in its damping capability.
+ Self-Actuation Potential: The material could be designed to self-actuate, using artificial tendons to change shape without the need for human intervention.
"Our metamaterial enables new capabilities, showing great potential for its incorporation into robotics, reconfigurable structures and space engineering," said Wenzhong Yan, corresponding author and postdoctoral scholar at UCLA's Samueli School of Engineering. "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."
"The general concept of contracting-cord metamaterials opens up intriguing possibilities on how to build mechanical intelligence into robots and other devices," Yan added.
The researchers suggest that this material could be used in self-assembling shelters, which might feature shells around a collapsible framework, or as compact shock absorbers with programmable damping for vehicles navigating rough terrains.
"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 Mehta, who is also a faculty member in UCLA's Department of Mechanical and Aerospace Engineering.
The study delves into the mechanical properties of these contracting-cord systems, including optimal bead alignment, self-assembly, and tunability, advancing the understanding of such metamaterials.
Research Report:Self-deployable contracting-cord metamaterials with tunable mechanical properties
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