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Self-healing thread changes from firm to flexible with just a bit of voltage

With a bit of voltage, a new fiber can go from firm to flexible in just a few seconds. The thread may not seem like much as first glance, but its versatility make it a promising new component for a number of applications, from rehabilitation to robotics.

Developed by researchers at École Polytechnique Fédérale de Lausanne (EPFL), the thread consists of a metal core encased in a silicon pipe. Heat causes the core to melt and the thread assumes the properties of the silicon layer, bending and flexing as needed within about 10 seconds. When the thread is cooled again, the metal core solidifies and holds its new shape.

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These properties also make the thread self-healing, as any dent or fracture in the metal core can be fixed by simply the melting and solidifying it again.

“Threads can be knitted, knotted, wrapped, and woven,” EPFL scientist Alice Tonazzini told Digital Trends. “They are versatile and allow easy integration in pre-existing bodies.”

As such, the fiber has a number of promising applications.

A Composite Thread that Varies in Rigidity

“The thread can be used to create the structure of robots that are expected to display multiple functionalities and adaptive behaviors,” Tonazzini explained. “An example is a robot whose skeleton become extremely soft and deformable on demand, for example for squeezing into a hole. Another example is a reconfigurable robot that can be easily morphed into different shapes that are preserved after cooling, thus enabling different locomotion modes.”

Within healthcare, the thread may be used in rehabilitation and surgery, as the basis for easily removable and reusable casts or surgical tools.

“It adapts to the anatomy of the patient when soft while having a protective and load-bearing capability when stiff,” Tonazzini said.

“In surgical tools and endoscopes, the thread can provide a tunable interaction with human tissues,” she added. “When soft, it will passively and safely adapt to cavities to be explored; when rigid, it will provide stiffness and stability to perform surgical operations.”

Tonazzini and her team recently published their work in Advanced Materials.