"Sometimes you want a robot, or machine, to be stiff," said Prof Shepherd. "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."
The material is said to combine a soft alloy called Field's metal with a porous silicone foam. In addition to its low melting point of 62°C, Field's metal was chosen because, unlike similar alloys, it contains no lead. The combination of stiff metal and soft foam means it can be stiff when called for, and elastic when a change of shape is required. The material is also claimed to be able to self-heal following damage.
To make the material 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 2mm; that can be tuned to create a stiffer or a more flexible material.
In testing of its strength and elasticity, the material is said to have shown an ability to deform when heated above 62°C, regain rigidity when cooled, then return to its original shape and strength when reheated.