Gears are a familiar part of our daily lives, helping machines of every size run smoothly—from cars and clocks to wind turbines and robots.
But for decades, scientists have been trying to shrink gears to microscopic sizes to build tiny engines that could work inside chips or even inside the human body.
Until now, the challenge was that no one could make the drive trains—the mechanical systems that transfer motion—small enough to power gears smaller than a tenth of a millimeter.
Researchers at the University of Gothenburg have finally broken this barrier with a radically different approach.
Instead of relying on traditional mechanical parts, they have figured out how to drive gears using light itself.
Their breakthrough, published in Nature Communications, could pave the way for the smallest motors ever created—small enough to fit within the width of a human hair.
The team built their gears out of silicon using standard lithography techniques, the same processes used to manufacture microchips.
But what makes these gears special is that their surfaces are patterned with optical metamaterials—tiny structures that interact with light in very precise ways.
When a laser beam is directed at the metamaterial surface, the light makes the gear spin. By changing the intensity of the laser, researchers can control the gear’s speed, and by adjusting the polarization of the light, they can even reverse its direction.
In the lab, the researchers demonstrated entire gear trains—systems where one gear drives another—powered entirely by laser light.
These gear trains could convert spinning motion into back-and-forth movement or operate microscopic mirrors that deflect light.
“We have built a gear train in which a light-driven gear sets the entire chain in motion,” explains lead author Gan Wang, a physicist at the University of Gothenburg. “This is a fundamentally new way of thinking about mechanics on a microscale.”
Because the gears are powered by light rather than direct physical contact, they avoid the limitations of mechanical couplings and can be made far smaller than ever before.
They can also be integrated directly onto microchips, opening possibilities for advanced lab-on-a-chip technologies, optical systems, and tiny machines that manipulate particles or fluids.
The gears themselves measure just 16 to 20 micrometers in diameter—roughly the size of a human cell.
That puts medical applications within reach. “We can imagine using the new micromotors as pumps inside the human body, for example to regulate flows,” says Wang. “I am also looking at how they could act as valves that open and close.”
The prospect of light-driven machines working inside chips or even living bodies marks a major step forward in nanotechnology.
What once seemed impossible—motors smaller than the width of a hair—may soon power the next generation of medicine and technology.
Source: KSR.
