Researchers have discovered a "shape-recovering liquid" that appears to defy the laws of thermodynamics. The liquid, which is made up of oil, water and magnetized particles,consistently separates into a form resembling a Grecian urn.
This discovery began when Anthony Raykh, a polymer science and engineering graduate student at the University of Massachusetts Amherst, was studying a mixture of oil, water and nickel particles in a vial. He shook the vial to create an emulsion — or a blend of liquids that don't mix. But instead of separating into a clear top and bottom, the mixture formed the shape of a Grecian urn. Even after shaking the vial over and over, it kept returning to this shape.
"That's really odd," study co-author Thomas Russell, a professor of polymer science and engineering at University of Massachusetts Amherst, told Live Science. It's strange, he explained, because typically when a mixture of liquids that don't blend return to equilibrium before emulsion, they want to minimize the interfacial area, or the boundary between the two liquids. This tendency to minimize the interfacial area is governed by the laws of thermodynamics, which describe how temperature, heat, work and energy are related in physical systems.
In typical emulsions of oil and water, the liquids form spherical droplets, which have minimal surface area. In comparison, the Grecian urn shape has a higher surface area. This higher surface area, which seems to contradict the laws of nature, puzzled the researchers.
After investigating this odd behavior, they found that interactions between the nickel particles "sort of took over" to create what appeared to be a violation of the laws of thermodynamics, Russell said. The particles created magnetic dipoles, a phenomenon where their magnetic poles attract each other, creating a field of "chains" on the liquid's surface. This interaction interferes with how the emulsion separates.
While Russell said researchers have previously examined the segregation of particles in oil-water mixtures — as Raykh had been doing — nobody else had conducted the same experiment. So, no other researchers had observed or reported the higher interfacial energy seen with the Grecian urn shape.
While at first glance this mixture seems to defy the laws of thermodynamics, Russell clarified that it's just a strange case of them. The scientists realized that the particles' magnetic interference played a role, as its influence created a higher interfacial energy, which resulted in the higher surface area-shape. And in general, the laws of thermodynamics apply to systems overall, not to the interactions between individual particles, Russell said.
The researchers published their findings on April 4 in the journal Nature Physics.
