Soon, Terminator style shape-shifting robots

A Terminator-style shape-shifting robot that can morph into a liquid state to squeeze through tight spaces and repair itself when harmed may soon become a reality.

Scientists have developed a new phase-changing material built from wax and foam that could allow even low-cost robots to switch between hard and soft states.

In the movie 'Terminator 2' the T-1000 robot changes into a liquid form to pass through tight spaces or to repair itself when damaged.

The material — developed by Anette Hosoi, from the Massachusetts Institute of Technology (MIT), and colleagues - could be used to build deformable surgical robots.

The robots could move through the body to reach a particular point without damaging any of the organs or vessels along the way. Robots built from the material could also be used in search-and-rescue operations to squeeze through rubble looking for survivors, Hosoi said.

Working with robotics company Boston Dynamics, researchers began developing the material as part of the Chemical Robots programme of the Defence Advanced Research Projects Agency (DARPA).

Controlling a very soft structure is extremely difficult: It is much harder to predict how the material will move, and what shapes it will form, than it is with a rigid robot.

So the researchers decided that the only way to build a deformable robot would be to develop a material that can switch between a soft and hard state, Hosoi said.

"If you're trying to squeeze under a door, for example, you should opt for a soft state, but if you want to pick up a hammer or open a window, you need at least part of the machine to be rigid," she said.

To build a material capable of shifting between squishy and rigid states, researchers coated a foam structure in wax.

They chose foam because it can be squeezed into a small fraction of its normal size, but once released will bounce back to its original shape.

The wax coating can change from a hard outer shell to a soft, pliable surface with moderate heating.

This could be done by running a wire along each of the coated foam struts and then applying a current to heat up and melt the surrounding wax. Turning off the current again would allow the material to cool down and return to its rigid state. In addition to switching the material to its soft state, heating the wax in this way would also repair any damage sustained, Hosoi said.

"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," said Hosoi.

The research was published in the journal Macromolecular Materials and Engineering.