Bending liquid by ... light

French and American scientists have found a way to bend and adjust the direction of the liquid only by the force of light. They used a laser beam to produce a surprisingly long, steady stream of fluid, narrower than a human hair. When changing the direction of the laser beam at another angle, it pushes the liquid into a hump.

This is the first time a laser beam has been used to force fluid to flow. The discovery could lead to advances in biomedical science by opening up a new way to control fluid flow through narrow conduits.

Wendy Zhang, a professor at the University of Chicago, accidentally witnessed the discovery while visiting colleagues at the University of Bordeaux. Zhang was invited to a lab where former scientist Jean-Pierre Delville observed a strange phenomenon after finishing the experiment in order to understand the behavior of the liquid under a weak laser beam.

Delville increases the intensity of the laser beam to see what might happen.

"He intensified and then saw this strange thing," Zhang said.

Zhang brought the idea back to Chicago and together with a former student, Robert Schroll, they embarked on a hypothesis about what had happened. "I think this is special because I know when the liquid is dissolved, and this time it's not like that," Zhang said.

Although heat can cause fluid to move, Zhang and his colleagues find that this is not the case in this case. Instead, it is the light pressure generated by the new light photons that force the fluid to move.

This pressure is so slight that it is often difficult to recognize, but the liquid used in the experiment in Bordeaux has an astounding surface, even to the extent that light can distort it.

"Basically it is soap," Zhang said. The liquid in the experiment was a mixture of water and oil that, when mixed together, exhibited unusual properties under certain conditions.

However, scientists need to carry out further research to confirm whether this finding can be extended for use in life.

T. An