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