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The new material being squashed under the weight of a wrench. Courtesy of the researchers.
A new, 3D printed, phase-changing material has been developed by researchers from Massachusetts Institute of Technology (MIT) which could have a major impact on the robotics industry. Built from wax and foam, the material can switch between its hard and soft states, meaning robots that are able to squeeze through small spaces and even repair themselves are now being hypothesized.
Developed by Anette Hosoi, a professor of mechanical engineering and applied mathematics at MIT, the material could be used to give robots the ability to deform into different shapes. Hosoi believes they could therefore be utilised in a variety of different applications, such as search-and-rescue operations to find people in wreckages. Another area of interest would be for surgical robots that could squeeze into blood vessels and traverse the body without harming the patient.
The material was developed as part of the Chemical Robots program set out by the Defense Advanced Research Projects Agency (DARPA). Hosoi worked in conjunction with Boston Dynamics based in Massachusetts and DARPA wanted a robot to be developed that was "squishy" and able to fit through tight gaps and then expand again once it has squeezed through, similar to an octopus.
However, it is one thing to create a material that is able to deform through small spaces, but in order for a robot to perform tasks that require exertion, the material must have the ability to become rigid, in order to apply pressure.
In addition to this, the manipulation of soft materials can be tricky especially when trying to predict how the material will move and what it can form.
You can’t just create a bowl of Jell-O, because if the Jell-O has to manipulate an object, it would simply deform without applying significant pressure to the thing it was trying to move.
Anette Hosoi - Professor of Mechanical Engineering and Applied Mathematics
The researchers then decided to try and develop a material that switches between these two desirable states; soft when needing to pass through gaps, and hard when needing to perform tasks.
Wax On, Wax Off
The MIT team considered what materials display similar characteristics to the desired new material. This led them onto using foam. When foam is squeezed, upon release of the force it will spring back to its original shape.
Squishy Robots
Video from YouTube - Massachusetts Institute for Technology (MIT)
The researchers coated this foam with wax. Upon heating, wax is able to change from being hard to soft and so was identified as a good starting point to develop the phase-changing material. If a wire is run along the coated foam struts and then a current applied to it, the resulting heat would be sufficient to melt the wax coating.
When the current is switched off, the material would then cool down and the wax would resoldify and become rigid once more. Not only would the foam return to its original shape, but any damage sustained to it can also be reversed.
The process to produce the material is surprisingly simple. A piece of polyurethane foam is placed into a bath of warm wax and then squeezed to encourage it to soak up the wax.
A 3D printer was used to further study the material and its properties. This allowed control of the foam lattice structure as well its struts and pores.
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
Nadia Cheng - Former Graduate Student, Part of the MIT Research Team
Upon testing, it became clear that the 3D printed material was more amenable to analysis than the polyurethane foam. It was also suggested by Professor Hosoi that stronger materials than wax could be used, such as solder.
I'll Be Back?
Magnetorheological and electrorheological fluids are the next materials under investigation by Hosoi and her research team. Consisting of liquids with particles suspended within them, these materials can be switched between a soft and rigid state via the application of a magnetic or electric field.
So for those of you who had nightmares following the 1991 movie, Terminator 2: Judgement Day of the terrifying T-1000 robot, I'm afraid to say that this development may be a step closer to creating robots just like the Skynet villain.