The newly-discovered shape-recovering liquids defy long-held expectations derived from the laws of thermodynamics, according to a team of physicists at the University of Massachusetts Amherst.
This image shows emulsion droplets stabilized by silica nanoparticles with remaining nickel nanoparticles on the droplet surface. Image credit: Raykh et al., doi: 10.1038/s41567-025-02865-1.
“Imagine your favorite Italian salad dressing,” said University of Massachusetts Amherst Professor Thomas Russell.
“It’s made up of oil, water and spices, and before you pour it onto your salad, you shake it up so that all the ingredients mix.”
“It’s those spices, those small bits of something else, that allow water and oil, which are normally mutually exclusive, to mix, a process called emulsification and which is described by the laws of thermodynamics.”
“Emulsification underlies a vast range of technologies and applications far beyond condiments,” said Anthony Raykh, a graduate student at the University of Massachusetts Amherst.
“One day, I was in the lab mixing up a batch of this scientific salad dressing to see what I could create — only instead of spices, I was using magnetized particles of nickel, because you can engineer all sorts of interesting materials with useful properties when a fluid contains magnetic particles.”
“I made a mixture, shook it up — and, in a complete surprise, the mixture formed this beautiful, pristine urn-shape.”
“No matter how many times or how hard I shook, the urn shape always returned.”
Using additional lab experiments and simulations, the researchers determined that magnetism, strong magnetism, explains the inexplicable phenomenon they had discovered.
“When you look very closely at the individual nanoparticles of magnetized nickel that form the boundary between the water and oil, you can get extremely detailed information on how different forms assemble,” said Professor David Hoagland, also from the University of Massachusetts Amherst.
“In this case, the particles are magnetized strongly enough that their assembly interferes with the process of emulsification, which the laws of thermodynamics describe.”
Typically, particles added to an oil-and-water mixture decrease the tension at the interface between the two liquids, allowing them to mix.
But in a twist, particles that are magnetized strongly enough actually increase the interfacial tension, bending the boundary between oil and water into a graceful curve.
“When you see something that shouldn’t be possible, you have to investigate,” Professor Russell said.
“While there’s no application for our discovery yet, we’re excited to see how this never-before-seen state can influence the field of soft-matter physics,” Raykh added.
The team’s work appears in the journal Nature Physics.
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A. Raykh et al. Shape-recovering liquids. Nat. Phys, published online April 4, 2025; doi: 10.1038/s41567-025-02865-1
