Researchers from QingDao University of Science and Technology have created a proof-of-concept optical tractor beam that can pull macroscopic objects via laser light.
In the study, the research team essentially amplified the force with which light can pull objects. They accomplished this by developing a composite structure made of graphene-silicon dioxide that, when irradiated with a laser, creates a reverse temperature difference—in other words, the side facing away from the laser warms up. This causes the gas molecules on their back side to receive more energy, pushing the object toward the laser’s source. When conducted in a rarified gas environment, the force was strong enough to move macroscopic objects.
Contactless manipulation of objects via light has already advanced to practical application, in instances like optical tweezers that hold individual cells and even atoms in place. However, these techniques have been limited to microscopic objects. But the results of this new study show that this may soon change.
“We found that the pulling force was more than three orders of magnitude larger than the light pressure,” said researcher Lei Wang. “In addition, the laser pulling is repeatable, and the force can be tuned by changing the laser power.”
Though the technology is promising, it is currently only a proof-of-concept. The scientists have identified several ways of improving it, such as developing a “systematic theoretical model” to predict the pulling force when accounting for parameters such as the object’s geometry, surrounding media, and more. The team would also like to adapt it to work for a wider range of air pressures, rather than just rarified gas environments.