Engineering Squishy Robots to Tackle Tricky Places

MIT engineers are developing 'phase-changing' materials for robots to squeeze into small spaces.

Professor Anette Hosoi and her team created technology made of foam and wax to deform the robots. Other members of the team include Hosoi's former graduate student Nadia Cheng and researchers at the Max Planck Institute for Dynamics and Self-Organization. The materials make it a viable and cheaper alternative to conventional, solid robots. Its unique composition enables it to shift between hard and soft states.

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Another study determined the material could be used in building a surgical robot. That robot would be able to travel through the human body without damaging other organs. Remember the Magic School Bus episode where Ms. Frizzle take the kids on a field trip into the human body? These robots could offer a less-exciting alternative to that episode.

Robots have already been successfully tested with the material integrated. Currently, the robots can squeeze through small holes and re-expand on the other side, much in the same way that octopi do.

However, one particularly interesting fact the researchers noticed soft-structure robots are hard to control. The motions are incredibly unpredictable compared to rigid robots. Thus, the researchers decided to develop a robotic structure which can transfer between solid and hard states.

“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 Hosoi.

How it Works

Surprisingly, the soft/rigid structure technology is simple. A foam layer is submerged in hot wax and squeezed to absorb the material. The foam provides a soft, pliable internal structure while the wax provides both solid and pliable characteristics depending on the temperature. Wax remains solid at cooler temperatures, but with a little heat, it becomes soft and able to squeeze through tight areas.

Currently, the temperature is altered by running a long wire through the structure. The wire acts a resistor which in turn produces heat.

The wax can also be heated to the point where it reaches a liquid state, healing any damage in the process.

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

The low-manufacturing costs means these robots could embark on dangerous missions. They could be used for search and rescue missions which would require them to sift through heavy and jagged rubble.

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The shape-changing materials could help research efforts all around the world. These robots are incredibly maneuverable, cheap to produce and highly effective.

“This work is a great demonstration of how thermally controlled rigidity-tuning could potentially be used in soft robotics.” concludes Carmel Majidi, an assistant professor of mechanical engineering at the Robotics Institute at Carnegie Mellon University, a non-affiliated member of the project.