The hypnotising patterns in these swirling soap films aren’t spontaneous: they’re being controlled by the invisible hand of electricity.
By applying an electric field to the suspended liquid, it starts to rotate. Changing the direction of the electric field can alter the direction of flow, and the field’s strength affects the speed of rotation.
“The rotating film is like a motor,” says Reza Shirsavar from the University of Zanjan in Iran and his colleagues, who created the set-up.
Their soap film was made from water, glycerine and detergent, a common recipe used in bubble-blowing mixtures. The rainbow of colours arises from the varying thickness of the soap film on the water.
But beyond stirring up your bubble bath, the technique could be applied to other types of films containing polar molecules. Liquid crystal films, for example, or compounds used to manufacture industrial chemicals, could be controlled in the same way.
Shirsavar’s team says the system could be used as a micro pump, perhaps even controlling the ebb and flow of fluids inside living systems.
The video was presented last week at the annual meeting of the American Physical Society Division of Fluid Dynamics in San Francisco, California.
