Light-Driven Gears Break Size Barrier for Micromotors

Gears are fundamental components in everything from watches and cars to robots and wind turbines. For decades, scientists have tried to shrink them down to the microscale to build tiny engines. However, progress stalled at around 0.1 millimetres because traditional mechanical drive trains could not be made any smaller.

Now, researchers at the University of Gothenburg and collaborators have overcome this limitation by using light instead of mechanical drive trains to power gears.

In their new study, the team demonstrates that microscopic machines can be driven by optical metamaterials nanoscale patterns that capture and control light. Using lithography, they fabricated silicon gears directly onto a microchip, with diameters as small as a few dozen micrometres. When a laser shines on the metamaterial, the gear spins. Its speed depends on the laser’s intensity, and its direction can be reversed by changing the polarization of the light

This marks a step toward creating light-powered micromotors. “We have built a gear train in which a light-driven gear sets the entire chain in motion,” says Gan Wang, first author of the study and a researcher in soft matter physics at the University of Gothenburg. “The gears can also convert rotation into linear motion, perform periodic movements, and even control microscopic mirrors to steer light.”

Because the gears are integrated directly onto chips and controlled by laser light—without physical contact—they can be scaled into more complex microsystems. “This is a fundamentally new way of thinking about mechanics on a microscale. By replacing bulky couplings with light, we can finally overcome the size barrier,” Wang adds.

The gears measure just 16–20 micrometres—comparable to the size of a human cell—opening the door to biomedical applications. For instance, the micromotors could act as pumps to regulate fluid flows inside the body or serve as tiny valves.

The full study is published in Nature Communications: “Microscopic Geared Metamachines.”

Source: https://www.gu.se/en/news/light-powered-motor-fits-inside-a-strand-of-hair