To this point, the one thing that saved us from being overtaken by sentient robots is the fact that a) they don’t exist and b) they’re easily identified as robots. That second bit might be changing, though: Scientists at MIT have developed what they’ve dubbed “squishy robots:” Robotics that can alter their shape and even repair damage on their own.

One can’t help but wonder how far science is from Terminator 2‘s T-1000. Fortunately, the researchers say the possible benefits include remote controlled surgery, since the flexible robots could move within the body without damaging organs. Or, picture a super-maneuverable robot squeezing through rubble to locate survivors in disaster situations.

Perhaps unsurprisingly, the project began as part of the Chemical Robots program of the Defense Advanced Research Projects Agency (DARPA), who were interested in robots that could maneuver, octopus-style, through tight spaces. Of course, this is challenging: Soft objects are not only more difficult to control than rigid ones, they’re also less capable of delivering a meaningful amount of force.

“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,” says Anette Hosoi, a professor of mechanical engineering and applied mathematics at MIT.

To meet both requirements, the team settled on a foam structure sheathed in wax. It’s shockingly simple, and done with materials purchased at a craft store: Soak the foam skeleton in melted wax, allow it to absorb, and you have the basic model. Run a current through it to heat up the wax, and the robot becomes flexible. Allow it to cool, and it’s rigid again. That same principle allows it to be “self-healing.”

“This material is self-healing,” Hosoi says. “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.”

For a more durable (but still simple) robot, something like solder could be used to replace the wax outer layer. 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.