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How to Turn Surgical Robots into Shapeshifters

A group of U.S. and German researchers think they've come upon a materials innovation that could enable deformable surgical robots--and perhaps other types of exotic medical devices.

Anette Hosoi, a professor of mechanical engineering and applied mathematics at MIT, and her former graduate student Nadia Cheng, worked alongside researchers at the Max Planck Institute for Dynamics and Self-Organization and Stony Brook University to experiment with phase-changing material built from wax and foam, according to MIT News.

The innovation was actually pretty simple: polyurethane foam placed in a bath of melted wax.

"A lot of materials innovation can be very expensive, but in this case you could just buy really low-cost polyurethane foam and some wax from a craft store," Cheng told MIT News.

The research team's work is described in a recent paper in the journal Macromolecular Materials and Engineering. They envision the material could be used in robots capable of moving inside the human body without damaging organs or blood vessels along the way. Another use involves robots capable to squeezing in between rubble in search and rescue operations.

MIT Squishy Robots
MIT researchers have been working on 3-D printed scaffolds that can morph from being rigid, left, to being soft and compliant, right. (Photo courtesy of MIT News)

Working with Waltham, MA-based robotics company Boston Dynamics, the researchers started developing the material as part of the Chemical Robots program of the Defense Advanced Research Projects Agency (DARPA).

Hosoi, Cheng, and others decided the foam was optimal because it can be squeezed to fraction of its normal size, but bounce back. The wax meanwhile can transform from hard to soft and pliable through moderate heating. This is possible by applying an electrical current via a wire run along each of the coated foam struts.

Turn off the current, and the wax returns to its rigid state. Better yet, the melting does away with any previous damage to the wax.

"This material is self-healing," Hosoi said. "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."

Hosoi, Cheng, and colleagues found they could further enhance their shape-shifting material through using a 3-D printer to carefully control the position of each of the struts and pores in a foam lattice structure. Hosoi also suspects the wax could be replaced by a stronger material such as solder.

Refresh your medical device industry knowledge at MEDevice San Diego, September 10-11, 2014.

The MIT team is also exploring unconventional materials for robotics, such as magnetorheological and electrorheological fluids that consist of a liquid with particles suspended inside. Such materials can switch from a soft to a rigid state when a magnetic or electric field is applied.

Chris Newmarker is senior editor of MPMN and Qmed. Follow him on Twitter at @newmarker.

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