New material paves way for morphing robots

The inventors of a simple material that can liquefy in order to repair itself claim it could lead to shape-shifting robots.

The engineers at the Massachusetts Institute of Technology (MIT) who are behind the wax and foam phase-changing material say it could be used to create deformable surgical robots for operating inside the body without damaging any organs.

They said that other robots built from the material, which can switch between hard and soft states, could change their shape to squeeze through tight spaces, for example on search and rescue missions.

The challenge was in creating a material that could be soft but also exert a reasonable amount of force on its surroundings, said lead researcher Prof Anette Hosoi.

‘You can’t just create a bowl of Jell-O, because if the Jell-O has to manipulate an object, it would simply deform without applying significant pressure to the thing it was trying to move,’ she said in a statement.

To create the material, the researchers placed low-cost polyurethane foam in a bath of melted wax then squeezed the foam to encourage it to soak up the wax, which could be replaced by a stronger material such as solder.

To study the material’s properties in more detail, the team then 3D printed a second version of the foam lattice structure, allowing them to carefully control the position each of the struts and pores.

Running a wire along each of the coated foam struts and applying a current to heat up and melt the surround wax would cause the material’s hard outer shell to become a soft, pliable surface.

This would also repair any damage sustained, said Hosoi. ‘This material is self-healing. So if you push it too far and fracture the coating, you can heat it and then cool it, and the structure returns to its original configuration.’

A 3D-printed soft, flexible scaffold that is coated in wax and is being compressed in a temperature-controlled chamber. Heating a composite whose wax coating has broken can enable the wax to soften and

Hosoi is now investigating the use of other unconventional materials for robotics, such as magnetorheological and electrorheological fluids. These materials consist of a liquid with particles suspended inside, and can be made to switch from a soft to a rigid state with the application of a magnetic or electric field.

The MIT team worked with researchers from the Max Planck Institute for Dynamics and Self-Organization and Stony Brook University, as well as robotics firm Boston Dynamics (now owned by Google) as part of the Chemical Robots program of the government’s Defense Advanced Research Projects Agency (DARPA).

The material is described in a paper in the journal Macromolecular Materials and Engineering.