Researchers have developed a method to control microscopic swimming robots using light patterns and the principles of Einstein’s theory of relativity. The technology is a potential first step toward deploying tiny robots in applications ranging from medicine to manufacturing.
One of the great challenges of development micro robots for practical applications, create those capable of navigating without the inclusion of large sensors and other electronics, which would make the machines too large to operate at the desired scale (such as inside a human body). In an effort to overcome this problem, physicists at the University of Pennsylvania created “artificial spacetime” to direct machines to travel in the same way that spacecraft or light do when traversing the universe.
The challenge was to guide the microscopic machines with enough precision that they could reach a specific point in space, without being hindered by the labyrinth’s walls. That’s where relativity came in. According to Einstein’s theory of general relativity, gravity bends space-time around objects with mass. Light and objects follow “straight” geodesics – the shortest paths – that look bent around masses. A good example of this is gravitational lensing: Although light travels in a straight line across the cosmos, it may appear bent and enlarged when they pass through the gravitational well of a massive object, such as a large galaxy cluster.
“We showed that the way EK robots behave in patterned light fields is identical to the paths light follows in general relativity,” lead study author Marc Miskinan assistant professor of electrical and systems engineering at the University of Pennsylvania, told LiveScience in an email. “Incredibly, you can use the robots as a gravity analog since the correspondence is exact. Alternatively, you can flip general relativity ideas to use them to guide robots: in the same way that gravity pulls objects together, you can guide robots to a specific location.”
Artificial space-time
To mimic the effect, the team modeled the maze as curved virtual space using relativity equations. Paths to the goal inside the maze became simple straight lines in the model. They then converted the model back to a 2D light map. Dark spots naturally attracted the robots, while lighter spots repelled them. The end point of the maze was the darkest point (kind of faux black hole), with obstacles that are more strongly illuminated.
Regardless of where they were first placed, the EK robots naturally followed these geodesics, avoiding walls automatically, as if they were sliding down in warped space. The team published their findings in November 2025 in the journal npj Robotics.
For Miskin, the study is a bridge between the worlds of physics and technology, “rather than a competition between them,” he said. “On the one hand, relativity and light are very well understood; connecting reactive control to them invites new ways of thinking and established tools for robotics. On the other hand, general relativity and optics are also very abstract (think bending of spacetime), while robotics is mechanistic and concrete (it’s very easy to understand why the robot does what it does). In addition to showing how new types of optics give robots according to known optics. a little more” insight into general relativity, especially in to explore the impact of “flat spacetimes” in 2D space, Miskin added.
While the maze study is a very early step, Miskin said practical applications could emerge within the next 10 years.
“Some use cases we’re interested in exploring include checking up teeth after a root canal, a kind of dental biopsy to make sure everything was removed, eliminating tumors after doing local measurements to confirm that cells are cancerous, or even, outside of bio, assembling microchips with tiny robotic helpers,” Miskin said. “The microworld is a fascinating place; I wouldn’t be surprised if these ideas are just the tip of the iceberg.”
