Researchers from the University of Würzburg have developed tiny robots, smaller than one micrometer, that are propelled by photon repulsion and capable of manipulating bacteria in a liquid environment.
Tiny robots, about 50 times smaller than the diameter of a human hair, are opening up new possibilities for working directly in the microscopic world. In a new study, researchers at the Julius Maximilian University in Würzburg, Germany, have succeeded in demonstrating light-powered nanorobots that can locate bacteria, collect them, transport them from one place to another, and release them at specific points.
The development is intended to address one of the central problems in the study of tiny biological systems: how to precisely control very small living bodies, such as single cells or bacteria, within a liquid environment. Until now, such manipulation required complex systems, and was severely limited in size, precision, and maneuverability. The new nanorobots offer a different way: using light as both an energy source and a means of steering.
The study, published in Nature Communications, was led by a team led by Prof. Bert Hecht from the University of Würzburg. The researchers relied on a particularly subtle physical principle: photon repulsion. When light is absorbed and emitted in a certain direction, each photon creates a tiny repulsive force. In ordinary objects, this force is almost insignificant, but when it comes to devices with a very small mass, even such a weak push can quickly move them and cause them to accelerate.
A robot powered by photons
In previous stages, the team developed tiny devices called microdrones. They included up to four plasmonic nanoantennas, which absorb light with certain properties and emit it in a specific direction. The directed emission creates the repulsive force that propels the device. In the current study, the researchers were able to shrink the robots even further, to a size of less than one micrometer, that is, less than one thousandth of a millimeter.
The key breakthrough was in simplifying the steering mechanism. Instead of a complex control system, the researchers exploited a natural property of the nanometer antenna wires inside the robot. The wires tend to align according to the polarization of the light that hits them. When you change the polarization of the light, the robot's direction also changes. This allows you to control the direction of its movement, while the propulsion itself continues to be based on photon repulsion.
Jin Qin, the lead experimental investigator on the study, explained that it is essentially a light-driven nanorobot that can detect and collect bacteria. He said that simplifying the design allowed the robots to reach a size where they can operate directly in the microbial world, almost like microscopic cleaning devices.
Bacteria collection and manipulation in a liquid environment
The new nanorobots are not only tiny, but also very agile. They can make sharp 90-degree turns at high speed, so they can scan large sample areas systematically and efficiently. They can then attract bacteria to them, carry them, transport them to another location, and release them in a controlled manner.
The researchers describe this as a kind of "cleaning" of a microscopic environment under laboratory conditions. This is not a tiny vacuum cleaner in the familiar sense, but a system that allows bacteria to be collected from a sample and transferred to specific points. Such a capability could aid research in microbiology, biomedicine, and fields where cells and bacteria need to be separated, concentrated, or arranged with high precision.
Even when the robots were carrying relatively large amounts of bacteria, they remained controllable. They moved slightly slower, but they continued to maneuver and change direction. This finding is important because it shows that the robots are not just operating under ideal conditions, but are capable of doing real work even when carrying biological payloads.
Prof. Hecht said the research demonstrates how light can be used not only to observe the microscopic world, but also to actively shape it. He said the idea of tiny "microbe cleaners" sounds futuristic, but the research already demonstrates the physical principles that make it possible.
The applications are still research-based, but the direction is clear: light-driven nanorobots could become a new tool in the study of bacteria, cells, and biological materials. In the future, they could help perform more precise experiments, separate bacterial populations, transport cells or particles, and perhaps even develop new methods for controlling complex microscopic environments.
Scientific source: Jin Qin, Carsten Büchner, Xiaofei Wu and Bert Hecht, “A nanoscale robotic cleaner”, Nature Communications, March 27, 2026. DOI: 10.1038/s41467-026-70685-9
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