Dynamic materials change mechanical properties

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Researchers at Case Western Reserve University in Cleveland Ohio have designed a polymer nanocomposite material that can exhibit reversible changes in mechanical properties, such as stiffness and strength, in response to a specific stimulus. 

Biomimicry Story

The tissue of some species can transition from hard to soft and back again in a matter of seconds. Once transitioned, no energy is required to keep the material in either state. This unique ability is achieved through the rearrangement of microfibers within the material itself, creating an ordered micro-structure as a hard material and a disordered micro-structure as a soft material. This type of tissue is called Mutable Collagenous Tissue, or MCT. For example, the sea cucumber has skin that can change from stiff to nearly liquid as part of the animal's defense-and-escape behavior. Once the sea cucumber has made itself rigid it can maintain that strength for as long as it needs until the threat is over. Its relative the starfish uses MCT to pry open clams. The starfish simply wraps around the clam, makes itself rigid, and locks its shape, creating a constant pull on the clam – without exerting energy. The clam has to keep burning energy to keep itself closed, and it eventually tires, rewarding the starfish with a tasty meal. Inspired by such versatile and dynamic natural materials, Jeffrey R. Capadona and his reserch team at Case Western Reserve University designed a new adaptive material using a solid polymer that transitions from the stiffness of a CD case to that of a rubber band. Initially, the team is using this for brain surgery where the material needs to be stiff during the procedure to implant it, but needs to be soft and pliable once it's in place.   

Challenges Solved

Potential applications for these and other adaptive materials are huge, from novel attachment systems to building materials. Imagine a flexible material that could be squeezed into place and then "set"; emergency medical braces that wrap around a broken limb, then stiffen; or even responsive building elements that change shape when they get wet or hot.

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