The usual materials used in manufacturing robots are hard such as metals and plastics, which allow little or no variations in shape and size. But researchers have been trying to create 'squishy robots' for years that can shift shape and adapt to their environment.

Scientists at the Massachusetts Institute of Technology (MIT) in the US led by Anette Hosoi, who is a professor of mechanical engineering and applied mathematics, have developed a material that is made from wax and foam which can switch between soft and hard states. The project is part of the Chemical Robots program of the Defence Advanced Research Projects Agency (DARPA).

The challenge was to create a very flexible and soft material that can harden when required. As Hosoi explains at MIT News: "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".

In order to achieve this, Hosoi and her team coated a foam lattice structure with wax. They chose these materials as foam can squeeze into a small size and then also go back to its original shape whereas wax can go from hard to soft when exposed to moderate heating. They then ran a wire through the foam structure and applied electric current to melt the wax. Once the current turned off, the wax got rigid again. Then the team formed 3D-printed another lattice structure, which they found easier to analyze.

If used to build robots, the new material may have many fascinating applications. Helen Knight explains that it can be used to make surgical robots that could enter the body without any damage to the vital organs. Other possible applications are rescue missions as these 'squishy robots' would be able to squeeze through debris.