New hybrid material can morph shape and self-heal

Cornell University engineering professor Rob Shepherd and his team have come up with a new hybrid material that can bring a futuristic concept to reality.

The metal-foam compound developed by the team is able to change shape when required and has the ability to self-heal following damage when heat is applied. The idea blends the rigidity and load-bearing capacity of humans with the ability to dramatically alter shape, like an octopus.

“It’s sort of like us – we have a skeleton, plus soft muscles and skin,” Shepherd said. “Unfortunately, that skeleton limits our ability to change shape – unlike an octopus, which does not have a skeleton.”

The material combines a soft alloy called Field’s metal with a porous silicone foam.  The Field’s metal was chosen because it contains no lead and has a low melting point of 144 degrees Fahrenheit.

The elastomer foam is dipped into the molten metal, then placed in a vacuum so that the air in the foam’s pores is removed and replaced by the alloy. The foam had pore sizes of about 2 millimeters; that can be tuned to create a stiffer or a more flexible material. When heated above 144 degrees, the material showed an ability to deform, regain rigidity when cooled, then return to its original shape and strength when reheated.

“Sometimes you want a robot, or any machine, to be stiff,” said Shepherd, whose group recently published a paper on electroluminescent skin, which also has applications in soft robotics.

“But when you make them stiff, they can’t morph their shape very well. And to give a soft robot both capabilities, to be able to morph their structure but also to be stiff and bear load, that’s what this material does.”

Check out this video of the material displaying shape memory and ability to self-heal through reheating.

www.engineering.cornell.edu