Wax Robots
July 15, 2014

Wax Robots

Terminator 2 is one of my favorite science fiction movies. It has great action and a not-so-terrible plot, which is all I can really ask for in an action movie – seriously, Expendables, you cannot even give me that? – plus a very interesting villain. I mean, sure, the T-1000 is not exactly the most in-depth movie villain, but he is interesting. Composed entirely of liquid metal and thus able to alter its form at will, including comprising weapons out of its own body and regenerating form damage, this was a machine unlike any other machine I had ever seen. Until then, robots were always things like the Terminator itself – the Arnold one – or Robocop. The idea of a soft-form robot was entirely new to my young mind, and I found it both intimidating and fascinating all at once. Unlike the T-101, which was little more than a hunter/killer robot, the T-1000 seemed almost alien. As with many other science fiction movies, it made me wonder if we would ever truly have the technology to be able to create something like that.

Of course, we still have yet to reach that level of technology. Still, we are making strides. Working with Boston Dynamics, Anette Hosoi, a professor of mechanical engineering and applied mathematics at MIT, Nadia Cheng, a former graduate student of Hosoi’s, and a team of researchers at the Max Planck Institute for Dynamics and Self-Organization and Stony Brook University has developed a phase-changing material built from wax and foam that is able to alter its own structure, changing from rigid to soft on command. Build as a part of the Chemical Robots program of the Defense Advanced Research Projects Agency, or DARPA, this material was inspired by the way octopuses are able to squeeze through tight spaces, narrowing their bodies and then expanding them again, and wanted to see if they could design a robot that could do the same thing. After all, having a soft body would be useful for traversing through narrow spaces but a rigid form is also needed for any level of manipulation of its environment (such as lifting or moving things) you want the robot to be able to perform.

For the material, foam was used because of its ability to be squeezed down into a fraction of its normal size only to return to its original shape when relieved of pressure. The team then used a wax coating because wax is able to change from a hard outer shell to a softer, more pliable form when heat is applied. This was done by running a wire along each of the struts in the design, applying a current to heat up and melt areas of the wax when desired. Turning off the current and allowing the structure to cool would allow it to cool and then harden once more. In building the material, the research team put polyurethane foam into a bath of melted wax, squeezing the foam so that it soaked up as much wax as possible.

Not only is this an incredibly inexpensive design, after all it is just low-cost polyurethane foam and wax, these wax robots are also self-repairing. The wax surface can crack by too much pressure, but a simply heating and cooling repairs any damage it might have suffered.

Here’s a video of this incredible substance.

Robots made of this incredible material could have many wonderful applications in medicine, allowing movement through the body without causing any unwanted damage, as well as search-and-rescue where rescue teams need to find someone trapped under rubble. Sure, its not quite the T-1000, but honestly that is probably for the best.

Image Credit: Annette Hosoi / Nadia Chang / MIT

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