Microscopic metavehicles are pushed and steered by light
Although solar-powered devices are now fairly common, Swedish scientists have created something a little different. They've built tiny "metavehicles" that are mechanically propelled and guided via waves of light.
Led by Prof. Mikael Käll and former PhD student Daniel Andrén, a team at the Chalmers University of Technology constructed the vehicles by coating microscopic particles with what are known as "meta-surfaces." The latter are described by the university as "carefully designed and ordered nanoparticles, tailored to direct light in interesting and unusual ways."
After the completed metavehicles were placed in a shallow dish of water, the scientists utilized a loosely focused laser to direct a plane wave of light onto them. It was found that by varying the intensity and polarization of the light, it was possible not only to propel the vehicles, but also to control their speed and to steer them – it was even possible to remotely guide them through patterns such as a figure 8.
"According to Newton’s third law, for every action there is an equal and opposite reaction – this means that when the light hits the meta-surface, and is deflected in a new direction, the meta-surface is also pushed away in the other direction," says Käll. "Imagine playing pool, when two balls hit each other and bounce off in different directions. In this case, the photons and the meta surface are like those two pool balls."
The team also managed to use the metavehicles to transport other objects – such as a microscopic polystyrene bead, a yeast particle and a dust particle – by pushing them along in front of themselves. It is therefore hoped that the technology may someday be utilized in applications such as moving micro-particles through solutions inside of or adjacent to cells.
A paper on the research was recently published in the journal Nature Nanotechnology. You can see some of the metavehicles in action, in the video below.