Cornell University has just announced what may be the smallest origami bird ever folded. While a typical origami animal is the product of the skillful hands of an artist, the Cornell bird has been bent by the strategic application of small electrical voltages. It had to be: the material the bird is made of is only 30 atoms thick.
Creative expression is not the aim of the university’s little bird – its construction foreshadows the principles and techniques that will lead to new generations of nanoscale mobile robots that “can enable the design of intelligent materials and interaction with the world of molecular biology “. said Dean Culver of the Army Research Laboratory of the United States Army Combat Capability Development Command, which supported the research.
According to Cornell Paul McEuen“We humans, our defining characteristic is that we have learned to build complex systems and machines on a human scale, and on huge scales as well. But what we haven’t learned to do is build machines on a small scale. And it’s a step in this fundamental, fundamental evolution of what humans can do, to learn how to build machines as small as cells. “
The main author of the article describing the little bird is a postdoctoral researcher Qingkun Liu. The paper, “Micrometer-Sized Electrically Programmable Shape Memory Actuators for Low-Power Microrobotics,” is the cover of the March 17 issue of the journal Science Robotics.
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The project is the result of a collaboration between physicist McEeuen and physicist Itai cohen, both from Cornell College of Arts and Sciences. This has already resulted in a (very) small herd of nanoscale machines and devices.
Cohen explains, “We want to have robots that are microscopic but have brains. So that means you have to have appendages driven by complementary metal-oxide-semiconductor (CMOS) transistors, basically a computer chip on a robot that is 100 microns per side.
The idea is that these tiny workhorses – a metaphor, there are no nanoscale origami horses yet – are released from a wafer, folded into the desired form factor, and then continued on. activities. Additional folding would give them movement as they worked, change shape to move their limbs, and manipulate microscopic objects. Researchers predict that these nanobots will eventually be able to achieve functionality similar to their big brothers.
The project combines materials science with chemistry, since folding is carried out with the strategic deployment of electrochemical reactions. Liu explains, “At this small scale, it’s not like traditional mechanical engineering, but rather chemistry, materials science and mechanical engineering, all mixed together.
“The hard part,” Cohen says, “is making the materials that respond to CMOS circuits. And that’s what Qingkun and his colleagues did with this shape memory actuator that you can drive with tension and make it keep a curved shape.
The robots are built from a nanometer thick layer of platinum covered with a film of titanium oxide. Rigid silicon oxide glass panels are attached to the platinum. A positive voltage creates oxidation, forcing the oxygen atoms in the platinum joints between the glass panels and forcing the platinum atoms out. This causes the platinum to expand, which bends the entire glass-platinum structure at a desired angle.
Because the oxygen atoms build up to form a barrier, a curvature is maintained even after the charge is turned off. To undo a fold, a negative charge can be applied which removes oxygen atoms from the seam, allowing it to relax and unfold.
All of this happens very quickly – a machine can fall back in just 100 milliseconds. The process is also repeatable. The team reports that a bot can flatten and fold back thousands of times, and all it takes is a single volt of electricity.
None of this really takes away what one might consider art. Figuring out how and where to apply tension to achieve the desired shape is not an easy thing to do. McEuen says, “A pretty remarkable thing is that these tiny tiny layers are only about 30 atoms thick, compared to a sheet of paper, which could be 100,000 atoms thick. So it’s a huge engineering challenge to figure out how to make something like this have the kind of functionality that we want.
Still, the group is getting pretty good at microscopic robotics and have already received the award. Guinness world record to assemble the smallest walking robot ever. The four-legged little man is 40 microns wide and between 40 and 70 microns long. They are aiming for a new record with their 60 micron wide origami bird.
According to Cohen, “These are major advancements over today’s advanced devices. We are truly in a class of our own.