This Motor Fits Inside a Human Hair. It’s Driven by a Laser

The Roadblock to Miniaturization

Creating increasingly smaller devices and structures has been a distinct field of science for a long time. However, for over three decades, researchers focused on miniaturization could not overcome one hurdle: building motors smaller than one-tenth of a millimeter. Recently, Swedish scientists managed to solve this problem by creating a miniature motor driven by laser light. They published their findings in the journal Nature Communications.

Gears Fail at the Microscale

What previously hindered such radical miniaturization? The gears and cogs that make up conventional engines require physical contact with each other, as well as appropriately constructed axles and bearings.

In normal-sized machinery, this is not an issue, but achieving adequate precision for motors smaller than a millimeter proved impossible. The gears did not rotate as they should, and the entire system quickly failed. Therefore, physicists from the University of Gothenburg decided to completely abandon conventional mechanics and use… light instead.

Silicon as a Building Material

The key to the breakthrough was the use of optical metamaterials. These are microscopic structures created from repeating elements. Crucially, the distance between these elements is smaller than the wavelength of light. This allows the structures to capture and control the light.

The researchers created gears from a silicon-based optical metamaterial. The diameter of each gear was just 16 micrometers—less than one-tenth of a millimeter. Human hair is thicker than this. This size is almost as small as some cells in the human body.

A Miniature light-powered motor

Breaching the previously unattainable size barrier is only one element of this groundbreaking discovery. Not only is the entire engine microscopically small, but you can also power it with light. When a laser beam hits the metamaterial, the gear begins to rotate. The light intensity controls the speed, and changing the polarization even allows the direction of movement to be reversed.

Small as a Cell, Powerful as a Futurist’s Dream

The ability to power these microscopic machines with light opens up completely new perspectives. The laser does not require constant contact with the mechanism and is easy to control—consequently, the micromotor can theoretically be scaled very easily.

Modern medicine stands to gain the most from this discovery. Gan Wang, the lead author of the study, multiplies the examples: “We can use the new micromotors as pumps inside the human body, for example, to regulate various flows. I am also investigating how they can function as valves that open and close.”

The light-powered motor Serving Medicine

Thanks to laser-controlled micromotors, one could precisely dose medication directly into diseased tissue. These machines could function as pumps regulating pressure in the eye or valves controlling the flow of bodily fluids. The small size offers unlimited possibilities. Additionally, the invention is made of silicon, just like modern microchips. This allows for easy integration with processors and even manufacturing during the same process. This light-powered motor could revolutionize drug delivery.

Read this article in Polish: Ten silnik mieści się w ludzkim włosie. Napędza go światło lasera