If you want to build a fully functional nanosized robot, you need to incorporate a host of capabilities, from complicated electronic circuits and photovoltaics to sensors and antennas.
But just as importantly, if you want your robot to move, you need it to be able to bend.
Cornell researchers have created micron-sized shape memory actuators that enable atomically thin two-dimensional materials to fold themselves into 3D configurations. All they require is a quick jolt of voltage. And once the material is bent, it holds its shape -- even after the voltage is removed.
As a demonstration, the team created what is potentially the world's smallest self-folding origami bird. And it's not a lark.
The group's paper, "Micrometer-sized electrically programmable shape memory actuators for low-power microrobotics," published in Science Robotics and was featured on the cover. The paper's lead author is postdoctoral researcher Qingkun Liu.
The project is led by Itai Cohen, professor of physics, and Paul McEuen, the John A. Newman Professor of Physical Science.
McEuen and Cohen's ongoing collaboration has so far generated a throng of nanoscale machines and components, each seemingly faster, smarter and more elegant than the last.
"We want to have robots that are microscopic but have brains on board. So that means you need to have appendages that are driven by complementary metal-oxide-semiconductor (CMOS) transistors, basically a computer chip on a robot that's 100 microns on a side," Cohen said.
Imagine a million fabricated microscopic robots releasing from a wafer that fold themselves into shape, crawl free, and go about their tasks, even assembling into more complicated structures. That's the vision.
"The hard part is making the materials that respond to the CMOS circuits," Cohen said. "And this is what Qingkun and his colleagues have done with this shape memory actuator that you can drive with voltage and make it hold a bent shape."
The machines fold themselves fast, within 100 milliseconds. They can also flatten and refold themselves thousands of times. And they only need a single volt to be powered to life.
The team has already been recognized by Guinness World Records for creating the smallest walking robot. Now, they hope to capture another record with a new self-folding origami bird that is only 60 microns wide.
The team is currently working to integrate their shape memory actuators with circuits to make walking robots with foldable legs as well as sheet-like robots that move by undulating forward. These innovations may someday lead to nano-Roomba-type robots that can clean bacterial infection from human tissue, micro-factories that can transform manufacturing, and robotic surgical instruments that are ten times smaller than current devices, according to Cohen.
Support was provided by the U.S. Army Combat Capabilities Development Command's Army Research Laboratory, the National Science Foundation, the Cornell Center for Materials Research, the Air Force Office of Scientific Research, and the Kavli Institute at Cornell for Nanoscale Science. Part of the work was performed at the Cornell NanoScale Science and Technology Facility.
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