Researchers Create Shape-shifting Materials

August 18, 2016 - Imagine a screwdriver that can morph into a wrench or wood chisel as needed, or vehicles that can change shape on demand. These are just a few applications possible with a new approach to materials design under development in the laboratory of Lorenzo Valdevit, UC Irvine Samueli School associate professor.

The shape-reconfigurable material is based on a modular system of bi-stable units with hinges that allow individual building blocks to be combined and recombined in different ways to create multi-stable structures. The living hinges allow the triangular units to snap into open or closed configurations. (A living hinge is a thin flexible connection with the same material as the two pieces it connects.)

By carefully tailoring the location of the hinges and the assembly of the modular blocks, one can design architected materials that morph between two or more desired shapes with great precision, while maintaining strength and providing energy absorption. This technique can be applied to a variety of constituent materials, including polymers, metals, ceramics and composites. Because the failure strain of the hinge material ultimately is critical to material selection, ongoing research is investigating how the hinge performance can be improved at the nanoscale. “Reducing the feature size in these materials is shown to be a possible solution for creating hinges that will undergo snapping without plastic deformation,” says the team in a paper published recently online in Advanced Materials.

One of the key benefits of this methodology, researchers say, is the reversibility between different stable states. This implies that the original or deformed configurations of the material can be infinitely recovered with no compromise in efficiency, integrity or structure life.

“This property of matter could pave the way for manufacturing of highly adaptable components that are fully reconfigurable based on functionality,” according to the paper. “1-D, 2-D and 3-D architected materials can be designed, enabling complex shape-morphing patterns.”

“Our work basically introduces a series of 2-D and 3-D designs with specific geometrical features for production of novel shape reconfigurable materials,” said Babak Hagparpanah, postdoctoral research and the paper’s first author. “These materials are modular… and the introduced designs are much stronger than any previously conceived multi-stable materials.”

Within several days after the paper was published, the team was contacted by the journal Nature, which highlighted their findings in its own publication.

“What I find fascinating about this research is that you can achieve unique mechanical properties simply by controlling the shape of a periodic cellular solid; complexity comes from geometry, not from the properties of the base material. This new design approach can open the door to so many new functionalities, all while working with existing materials,” said Valdevit.

-- Anna Lynn Spitzer


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