Microrobotics researchers have been working for decades, in a seemingly futile attempt, to keep up with the miniaturization that has been achieved in the field of microelectronics. Although rudimentary microscopic robots have been developed, they have failed to take full advantage of conventional silicon electronics and so are limited in their functionality. Specifically, no one has developed an actuator at micrometer resolutions that can work with semiconductor processing and be triggered using conventional electronic signals.
Now, researchers from Cornell University are reporting in the journal Nature that they have successfully created millions of sub-hundred-micrometer walking robots that operate using conventional electronics. These are so small, about the size of paramecium, that hundreds of them can pass through a hypodermic needle at the same time.
The robots feature four electrochemical actuators as legs that connect to silicon photovoltaics that serve as the processing center.
“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 Paul McEuen, one of the scientists that led the project. “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 make the robots, the researchers used extremely thin platinum strips which had a layer of titanium on one side. When a positive electric charge is applied to the platinum, negative ions from the nearby environment show up to balance out the charge. The same ions cause the platinum to expand and flex the leg. Polymer chunks on the metal strips allow for the creation of bending points, emulating the knees or ankles.
Each robot has tiny photovoltaic panels that can be targeted by an external laser to give the robot commands. In this case, the team was able to trigger the movement of individual legs of the robots and therefore the direction and speed of their locomotion.
“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 Itai Cohen, another leader of this research. “This is really just the first shot across the bow that, hey, we can do electronic integration on a tiny robot.”
Remarkably, a single 4-inch silicon wafer can be used to manufacture about one million of the new robots using existing lithography processes. Though they’re still pretty simple devices, these robots are simply a proof that it should be possible to build ever more complex microscopic robots that may one day be used in the human body.
Here’s a Nature video explaining the workings of the new robots:
Study in Nature: Electronically integrated, mass-manufactured, microscopic robots