May 31, 2014
MIT Researchers Work Towards Printable Robots That Self-Assemble When Heated
Brett Smith for redOrbit.com - Your Universe Online
Two research papers presented at the IEEE International Conference on Robotics and Automation in Hong Kong this week described the latest evolution in the on-going pursuit of printable robots.
The first paper identifies a system that can take digital specifications of a 3D shape and generate two-dimensional patterns that might allow some plastic to replicate itself via self-folding.
The second paper describes how to build electrical components from self-folding materials. The scientists present designs for this system that would become resistors, inductors, and capacitors, along with sensors and actuators, which allow for robotic movements.
"We have this big dream of the hardware compiler, where you can specify, 'I want a robot that will play with my cat,' or 'I want a robot that will clean the floor,' and from this high-level specification, you actually generate a working device," Daniela Rus, an electrical engineering professor at MIT, said in a recent MIT statement.
"So far, we have tackled some subproblems in the space, and one of the subproblems is this end-to-end system where you have a picture, and at the other end, you have an object that realizes that picture,” Rus said. “And the same mathematical models and principles that we use in this pipeline we also use to create these folded electronics."
The new system builds on previous efforts by accurately manipulating the angles at which a heated page folds. The team created the folding sheet by sandwiching a sheet of polyvinyl chloride (PVC) in between two sheets of firm polyester perforated with slits of distinct widths. When the sandwich is heated, the PVC contracts, and the slits close. The PVC is effectively shaped where edges of the polyester film press up against one another.
Now, if a narrow slit in the top polyester film sits above a different wider slit parallel to it in the bottom film, when the PVC contracts, the edges of the top slit will push against one another, but there will still be a space between the edges of the bottom slit. The whole sheet will then flex downward until the bottom edges also meet. The resulting angle is a result of the difference in the widths of the top and bottom cuts.
Rus said that determining the differences in widths between slits is a highly-complex process, more complex that simply folding sheets of paper into various shapes.
"You're doing this really complicated global control that moves every edge in the system at the same time," the MIT engineer said. "You want to design those edges in such a way that the result of composing all these motions, which actually interfere with each other, leads to the correct geometric structure."
The second paper describes how a similar concept could be used to design foldable electronic components. A sensor designed by the team resembles an accordion and each of the accordion folds contains an individual resistor. When the folds are compacted together, the total resistance of the tiny device changes proportionally.