Researchers used Einstein’s relativity theory to guide microscopic robots through complex paths without onboard electronics.
Physicists at the University of Pennsylvania have developed a way to steer microscopic swimming robots using patterned light and principles from Einstein’s theory of relativity. The tiny machines successfully navigated a maze by following light patterns that mimicked the curved space around black holes.
The technology solves a major problem in microrobot design. Small machines cannot carry bulky sensors or processors, making precise navigation nearly impossible. The new method uses external light to guide the robots, keeping them small enough to work inside the human body.
Lead study author Marc Miskin, an assistant professor of electrical and systems engineering at the University of Pennsylvania, led the research team. They created what they call “artificial space-time” to direct the robots the same way gravity directs spacecraft and light across the universe.
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The robots are about 100 microns wide, roughly the thickness of a human hair. Each electrokinetic swimming robot has tiny solar cells with electrodes on both ends. When light hits the solar cells, they power the electrodes, creating an electric field that pushes the robot through liquid.
The team faced the challenge of guiding these machines through a maze without hitting walls. They turned to Einstein’s general relativity for answers. The theory describes how gravity bends space-time around massive objects, making light appear to curve when it passes near stars or black holes.
“We showed that the way EK robots behave in patterned light fields is identical to the paths light follows in general relativity,” Miskin told Live Science. “Amazingly, you can use the robots as a gravity analog since the correspondence is exact.”
The researchers built a virtual model of the maze using relativity equations. They turned complex paths into simple straight lines in curved space. Then they converted the model back into a two-dimensional light map. Dark areas attracted the robots, while bright areas pushed them away. The target point became the darkest spot, acting like a fake black hole.
The team published their findings in November 2025 in the journal npj Robotics. No matter where the robots started, they followed the light patterns naturally and avoided walls as if sliding downhill in warped space.
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Miskin sees this research as a bridge between physics and practical technology. Relativity and light are well understood, but robotics feels concrete and mechanical. The experiments give researchers new tools for both fields.
The maze study is an early step. Practical applications may arrive in the next 10 years. Miskin’s team wants to explore using these robots for medical checks after root canals, confirming tumor removal during cancer treatment, or helping assemble tiny computer chips.
“The microworld is a fascinating place; I wouldn’t be surprised if these ideas are just the tip of the iceberg,” Miskin said.
