Microscopic robot takes first steps

Microscopic robots have the potential to explore worlds too small to see with the human eye. But making tiny machines that combine moving parts with onboard electronics has been a significant challenge. Researchers at Cornell University have now borrowed techniques from the semiconductor manufacturing industry to make the first walking robots the size of microbes.

The new water-wading robots use actuators that rely on electrolytes in solution to overcome drag and walk around (Nature 2020, DOI: 10.1038/s41586-020-2626-9).

The researchers fabricated micron-scale robots using the same technology used to make the electronics in cell phones and computers. They equipped the tiny machines with leg-like actuators powered by photovoltaic cells. The actuators are composed of an ultrathin layer of platinum—only a dozen atoms thick—that’s patterned with an inert graphene cap. When the actuator is charged, anions adsorb to the exposed metal surface and cause the material to bend along origami-inspired folds. The researchers made a million of these robots, which are about 70 microns across, on a 100 mm silicon wafer.

The researchers freed the robots from the wafer into solution on a microscope slide. They used a laser to direct the robot to walk across the slide, alternating pulses to each set of legs.

The new robots don’t have processing circuits yet, and they’re still limited in maneuverability. But the integration of functional actuators with silicon-based electronics means that “now we have the opportunity to build microscopic robots that have smarts,” says Marc Miskin, an electrical engineer at the University of Pennsylvania, who led the study while still at Cornell. His team is exploring ways to incorporate microsensors and solar cells that could eventually lead to autonomous microbots.

Michael Strano, a chemical engineer at the Massachusetts Institute of Technology, who was not involved in the study, says he’s impressed by the sophisticated fabrication of the robots. “Putting legs onto a silicon chip and then getting it to walk is a major feat,” he says.