The tiny robots start with thin, flat wafers of silicon, gold, and plastic.
It’s the heat from the electric current that causes them to flex along excavated grooves, flexing themselves into grippers, little boxes, even bee-sized paper cranes, and moving in more intricate ways like most microbots.
This is engineering inspired by origami, the Japanese art of paper folding, and the potential applications, according to University of Michigan engineering professor Evgeny Filippov, run the gamut from plumbing to high-tech surveillance.
“You can get these robots with a small sensing range, so maybe if you have a leak in your pipes, you flush it down your drain and it will figure out where the leak is,” said Filipov, a civil engineer by training. “You could have little reconnaissance drones.”
Or machines that you can swallow to help find canker sores, machines that can inspect hard-to-reach places inside buildings, and machines that can be packaged to test materials on a large scale.
They weren’t there yet. But Filipov and his collaborators have developed a more efficient way to make tiny, three-dimensional robots. This comes from origami.
Origami is the Japanese art of paper folding, although it likely has its roots in China, where paper was invented in the early second century. The practice of paper folding spread in Japan hundreds of years later, first as part of Shinto religious rituals and later as an art form.
The most important rules of origami in its modern version are no cutting and no gluing.
Engineers and mathematicians are finally starting to take an interest. They were doing origami conferences in the late 80’s.
But a program created a decade ago by the Air Force Research Laboratory and the National Science Foundation, called Origami Design for Engineering Innovation Self-Assembly Systems Integration, kickstarted origami research in the United States.
University of Michigan professor and students create origami-inspired structures
“Origami is getting more and more complex,” said Larry Howell, a professor of mechanical engineering at Brigham Young University, whose lab has used origami principles to design foldable solar arrays for spacecraft, fast-deploying ballistic shields, and even medical devices. [origami artists] We were able to accomplish and get certain types of movements that we would not have been able to do with our traditional engineering approaches.”
Filippov came to origami-based engineering as a civil engineering graduate student after realizing that the methods he was using to study how buildings and bridges behave during earthquakes were also useful for understanding origami-based structures.
“What it allows us to do is look at the structure from an outside perspective and understand where it is stiff, and why is it rigid or flexible?” He said.
Other work in his lab focuses on ways in which bending and folding can add strength and stiffness to flat surfaces.
“This is called the hyperbolic origami equivalent,” he said, holding a piece of paper that had been bent to the edges and bent in the middle like a butterfly rendered in a strange geometric shape. “When you take a piece of paper, usually, it’s very hard to form surfaces like this.”
But, when you do, the result is a structure that keeps its shape in more than one position.
“Imagine you have something that you want to deploy and then undo and you want it to remain stable both in that undo state, and then when you pull it back and you don’t want it to move too much between those,” he said. “You can use the same ideas.”
The idea is to create structures that can be stored and transported flat but spring to three-dimensional life when it’s time to use them.
Maria Redotti, one of the doctoral students in his lab, is working on the problem of how the transposition of structures from one form to another can happen practically in the field.
“Now I can move the structure to any point along the track,” she said, showing the spring struts. “For the most part, I have to apply a much smaller force now, and it stays where I put it. So you can imagine how useful that would be as a big deployable bridge.”
Other students are already working on deployable bridges, collapsible boats, collapsible traffic cones, woven roofs, and other applications of the production process used to make microbots.
Filippov’s work on small devices was funded by the Defense Advanced Research Projects Agency, better known as DARPA, the organization responsible at least in part for the existence of the internet, GPS technology, and self-driving cars.
There are still problems to solve, said Ken Oldham, a professor of mechanical engineering at UM who works on microsystems dynamics and control and a collaborator on the project, largely related to integrating energy sources into machines.
“The battery cannot necessarily be made by the same process as other batteries,” he said.
But most small robots are very expensive and the ability to start with a flat sheet of material that then bends and shapes itself into “as large a robot or complete system as possible… helps point you toward a more useful technology.”
Filippov sees the potential to manufacture them one day in the “hundreds of thousands”.
“If you want to monitor things spatially, that would be a very efficient way to do that, so for sensing and inspection, of course, militaries are interested in using surveillance and things like that,” he said.
He envisions them one day—”and maybe 20, maybe 50 years from now”—working together like swarms of bees.
“If we could really look at that scale of what bees are capable of doing, you have about 40,000 to 80,000 bees in a colony. They interact. They work together. They take material out of the field, they gather it together, they collect it, they bring it into their home, they make food.” That would be really cool. To have hundreds of thousands of these robots working together to do something bigger.”
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