A team of scientists from Cornell University and the University of Pennsylvania has developed a new class of microscopic robots that incorporate semiconductor components, allowing them to be controlled — and made to walk — with standard electronic signals.
Miskin et al built microsopic robots that consist of a simple circuit made from silicon photovoltaics and four electrochemical actuators; when laser light is shined on the photovoltaics, the robots walk. Image credit: Miskin et al, doi: 10.1038/s41586-020-2626-9.
The new walking robots are about 5 microns thick, 40 microns wide and between 40 and 70 microns in length.
Each consists of a simple circuit made from silicon photovoltaics that essentially functions as the torso and brain and four electrochemical actuators that function as legs.
The robots operate with low voltage (200 millivolts) and low power (10 nanowatts), and remain strong and robust for their size.
“In the context of the robot’s brains, there’s a sense in which we’re just taking existing semiconductor technology and making it small and releasable,” said co-lead author Professor Paul McEuen, of Cornell University.
“But the legs did not exist before. There were no small, electrically activatable actuators that you could use. So we had to invent those and then combine them with the electronics.”
The robots developed by Miskin et al are roughly the same size as microorganisms like Paramecium. Image credit: Miskin et al, doi: 10.1038/s41586-020-2626-9.
Using atomic layer deposition and lithography, Professor McEuen and colleagues constructed the legs from strips of platinum only a few dozen atoms thick, capped on one side by a thin layer of inert titanium.
Upon applying a positive electric charge to the platinum, negatively charged ions adsorb onto the exposed surface from the surrounding solution to neutralize the charge.
These ions force the exposed platinum to expand, making the strip bend.
The ultra-thinness of the strips enables the material to bend sharply without breaking.
To help control the 3D limb motion, the scientists patterned rigid polymer panels on top of the strips.
The gaps between the panels function like a knee or ankle, allowing the legs to bend in a controlled manner and thus generate motion.
The authors control the robots by flashing laser pulses at different photovoltaics, each of which charges up a separate set of legs.
By toggling the laser back and forth between the front and back photovoltaics, the robot walks.
“While these robots are primitive in their function — they’re not very fast, they don’t have a lot of computational capability — the innovations that we made to make them compatible with standard microchip fabrication open the door to making these microscopic robots smart, fast and mass producible,” said co-lead author Professor Itai Cohen, also from Cornell University.
“This is really just the first shot across the bow that, hey, we can do electronic integration on a tiny robot.”
The team is exploring ways to soup up the robots with more complicated electronics and onboard computation — improvements that could one day result in swarms of microscopic robots crawling through and restructuring materials, or suturing blood vessels, or being dispatched en masse to probe large swaths of the human brain.
“Controlling a tiny robot is maybe as close as you can come to shrinking yourself down,” said lead author Dr. Marc Miskin, from the University of Pennsylvania.
“I think machines like these are going to take us into all kinds of amazing worlds that are too small to see.”
The team’s work was published in the journal Nature.
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M.Z. Miskin et al. 2020. Electronically integrated, mass-manufactured, microscopic robots. Nature 584, 557-561; doi: 10.1038/s41586-020-2626-9
This article is based on a press-release provided by Cornell University.
