Researchers create a million microscopic robots

Researchers from the University of Pennsylvania and Cornell University have harnessed the latest nanofabrication techniques to create bug-shaped robots that are wirelessly powered, able to walk, able to survive harsh environments and tiny enough to be injected through an ordinary hypodermic needle.

Marc Miskin, an assistant professor of electrical and systems engineering at the University of Pennsylvania, and his colleagues have spent the past several years developing a multistep nanofabrication technique that turns a 10 cm specialised silicon wafer into a million microscopic robots in just weeks. Miskin presented his research at the American Physical Society March Meeting, held in Boston from 4–8 March.

The robots’ bodies, each measuring just 70 µm long (about the width of a very thin human hair), are formed from a superthin rectangular skeleton of glass topped with a thin layer of silicon into which the researchers etch its electronics control components and either two or four silicon solar cells — the rudimentary equivalent of a brain and organs. As noted by Miskin, “We’re taking technology developed by the semiconductor industry and using it to make tiny robots.”

Each of a robot’s four legs is formed from a bilayer of platinum and titanium (or alternatively, graphene). The platinum is applied using atomic layer deposition, which Miskin described as “like painting with atoms”. The platinum-titanium layer is then cut into each robot’s four 100-atom-thick legs.

“The legs are super strong,” Miskin said. “Each robot carries a body that’s 1000 times thicker and weighs roughly 8000 times more than each leg.”

Montage: the robots can explore their environment by walking, travelling at speeds comparable to crawling cells. Image credit: Marc Miskin.

The researchers shine a laser on one of a robot’s solar cells to power it. This causes the platinum in the leg to expand, while the titanium remains rigid in turn, causing the limb to bend. The robot’s gait is generated because each solar cell causes the alternate contraction or relaxing of the front or back legs.

The researchers first saw a robot’s leg twitch several days before Christmas 2017, in what Miskin described as “the first proof of concept”. They are now at work on smart versions of the robots with onboard sensors, clocks and controllers.

Miskin is also aware that the current laser power source would limit the robot’s control to a fingernail-width into tissue. He is now thinking about new energy sources, including ultrasound and magnetic fields, that would enable the robot to make incredible journeys into the human body for missions such as drug delivery or mapping the brain.

“We found out you can inject them using a syringe and they survive,” he said. “They’re still intact and functional, which is pretty cool.”

Top image caption: The robots are built massively in parallel using nanofabrication technology: each wafer holds 1 million machines. Image credit: Marc Miskin.

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