Microscopic Robots Powered by Light Could Aid Medical Diagnostics

Using novel nanofabrication techniques, researchers from the University of Pennsylvania and Cornell University have built micro-robots made from silicon and powered by solar cells. One million functional microscopic robots can be produced from a 4-in. silicon wafer.

Researchers have created tiny, functional, remote-powered, walking robots, developing a multistep nanofabrication technique that turns a 4-in. specialized silicon wafer into a million microscopic robots in just weeks. Each one of a robot’s four legs is just under 100 atoms thick, but they propel the tiny robots, powered by laser light hitting the robots’ solar panels. Robots are built massively in parallel using nanofabrication technology: Each wafer holds 1 million machines. Courtesy of Marc Miskin.

The robots’ bodies are formed from a superthin rectangular skeleton of glass topped with a thin layer of silicon, into which the researchers have etched electronics control components and either two or four silicon solar cells. Each of a robot’s four legs is formed from a bilayer of platinum and titanium (or alternately, graphene). The platinum is applied using atomic layer deposition. The platinum-titanium layer is then cut into each leg.

Robots can explore their environment by walking, traveling at speeds comparable to crawling cells. Courtesy of 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, causing the limb to bend. The robot’s gait is generated when each solar cell causes the alternate contraction or relaxing of the front or back legs. The legs of the robots impose low power requirements yet can carry loads ten thousand times their own weight. Actuation only requires 200 mV signals, facilitating straightforward integration with silicon microelectronics, the researchers said.

The teams at Penn and Cornell are now at work on smart versions of the cellular-sized robots that could include onboard sensors, clocks, and controllers. Because the current laser power source will limit amrobot’s control to a fingernail-width into tissue, the researchers are investigating new energy sources, including ultrasound and magnetic fields, that would enable these robots to journey into the human body for missions such as drug delivery or mapping the brain.

The cell-sized robots can explore their environment, be manufactured en masse, and carry the full power of silicon-based information technology. They are able to survive harsh environments and tiny enough to be injected through a hypodermic needle. “We found out you can inject them using a syringe and they survive — they’re still intact and functional,” said professor Marc Miskin.

The research was presented at the American Physical Society March Meeting 2019 in Boston, Mass.

Releasing 10,000 robots massively in parallel (real time). Courtesy of Marc Miskin.