Light is known to have the ability to move microscopic objects as demonstrated in the Nobel Prize-winning research of Arthur Ashkin on the discovery of optical tweezers and their application to biological research. He shares the 2018 Nobel Prize in Physics award with Gérard Mourou and Donna Strickland.
But now, researchers from the Chalmers University of Technology have succeeded in creating microscopic metavehicles that are powered by light. Unlike the optical tweezers that use highly focused laser beam to control tiny particles, this innovation showed that even an unfocused light can maneuver microscopic particles in complex and precise ways, and can even transport other objects.
How Does Light Maneuver the Microscopic Metavehicles?
In the research, titled "Microscopic Metavehicles Powered and Steered by Embedded Optical Metasurfaces" published in Nature Nanotechnology, researchers described how they created their tiny vehicles.
Lead researcher Professor Mikael Käll and his former Ph.D. student Daniel Andrén created the metavehicles by coating microscopic particles with metasurfaces, New Atlas reported. Researchers defined metasurfaces as ultra-thin arrangements of nanoparticles that are carefully designed and organized to direct light in unusual ways.
After coating them, the team placed the metavehicles in a shallow dish of water and used a loosely focused laser to direct light onto the tiny vehicles. Through a mechanical process, the metavehicles could be moved by varying the intensity and polarization of the light. Researchers noted that the heat generated by the light did not affect the process
They also found that they can control the speed and direction of the metavehicles when navigating them in different and complex patterns, such as creating figures of eight.
They explained that it demonstrates Newton's third law of motion: for every action, there is an equal and opposite reaction. When light hits the metasurface, it is deflected into another direction while the metasurface is also pushed to another direction. The team compared it to playing pool when two balls hit each other but bounce off in different directions.
Metavehicles Can Trasport Other Objects As Well
According to Science Daily, the team also experimented on transporting small particles around the tank. They used the metavehicles to push microscopic objects, proving that they can easily transport even a microscopic polystyrene bead, a yeast particle, and even a dust particle that is 15 times larger than the metavehicles on a water surface.
As of now, the team has not identified yet any practical use for their discovery. But they believe that the fundamental nature of the metavehicles could mean that they would have future uses.
Käll explains that the exploration of using light in moving objects is interesting although they are not yet fully understood. Nonetheless, its applications that drive studies such as theirs could lead to the exploration of different possibilities. For now, it shows its promising potential application, like moving particles through cell solutions.
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