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Microscopic robots controlled by standard signals

Technology News |
By Ally Winning

The robots, which are roughly the same size as microorganisms like paramecium, provide a template for building even more complex versions that utilize silicon-based intelligence. They can be mass produced, say the researchers, and may someday travel through human tissue and blood.

The new robots – which are about 5 microns thick, 40 microns wide, and range from 40 to 70 microns in length – represent a new class of voltage-controllable electrochemical actuators that operate at low voltages (200 microvolts), low power (10 nanowatts), and are completely compatible with silicon processing, say the researchers. Each bot consists of a simple circuit made from silicon photovoltaics – which essentially functions as the torso and brain – and four electrochemical actuators that function as legs.

“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,” says Paul McEuen, the John A. Newman Professor of Physical Science and who co-chairs the Nanoscale Science and Microsystems Engineering (NEXT Nano) Task Force. “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.”

To construct the legs, the researchers used atomic layer deposition and lithography and 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, say the researchers, enables the material to bend sharply without breaking. To help control the 3D limb motion, the researchers 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 robots are controlled by the researchers 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,” says professor of physics Itai Cohen. “This is really just the first shot across the bow that, hey, we can do electronic integration on a tiny robot.”

Because they are made with standard lithographic processes, the robots can be fabricated in parallel. About 1 million bots fit on a four-inch silicon wafer.

Looking ahead, the researchers say they are 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,” says Marc Miskin, an assistant professor at the University of Pennsylvania and the lead author of a study on the research. “I think machines like these are going to take us into all kinds of amazing worlds that are too small to see.”

For more, see “Electronically integrated, mass-manufactured, microscopic robots.”

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