A student experimenting with liquids and magnetic substances in the laboratory might have inadvertently discovered an “anomaly” in the principles of thermodynamics, as stated by the researchers behind a recent study inspired by their findings. This discovery involves a peculiar "shape-restoring fluid" that adopts the form of a Greek vase regardless of how vigorously it is agitated.
Some liquids simply refuse to combine: consider the simple case of oil and water. When you attempt to mix these two familiar substances, the lighter oil will rise above the water due to the differences in their internal bonding forces.
In water (H0), the part of the molecule associated with oxygen carries a partial negative charge , and the hydrogen end carries a partial positive charge. This leads to molecules attracting each other weakly, thus forming (under suitable temperature conditions) our beloved liquid. On the other hand, oils lack such charged polar ends. Consequently, oils are not drawn to water and resist mixing with it; achieving this mixture would require breaking several intermolecular bonds. water's hydrogen bonds .
Nevertheless, it is achievable to blend oil and water together through the use of a surfactant.
"When a detergent molecule comes into contact with a nonpolar substance like oil, it inserts its nonpolar section among the nonpolar molecules within the oil," as stated in "Exploring Our Fluid Earth" from the University of Hawai'i. explains As its nonpolar region bonds with the oil, its charged part turns outward and latches onto water molecules instead. Once numerous detergent molecules bind to an oily globule, they encase it, forming a microscopic sphere where the oil core is enveloped by detergents. Such spheres can be readily swept away into the aqueous solution.
Certainly, it’s not only soaps that act as surfactants. For example, in mayonnaise, the surfactant is lecithin derived from the egg yolk .
"Think of your preferred Italian salad dressing," said Thomas Russell, Silvio O. Conte Distinguished Professor of Polymer Science and Engineering at UMass Amherst and one of the paper's lead authors. statement It consists of oil, water, and spices. Before drizzling it over your salad, you should shake it well to blend all the components.
In this illustration, the surfactants act as the spices, enabling the two substances to briefly blend together. This phenomenon is referred to as emulsification , and is thoroughly explained by the principles of thermodynamics.
This is where things get intriguing. Graduate student Anthony Raykh from UMass Amherst decided to experiment with various immiscible fluids. In his experiments, he opted for magnetized nickel particles because they allow for the creation of numerous novel substances with valuable characteristics, as stated by Raykh. After vigorously agitating these liquids, an unexpected outcome occurred: the blend unexpectedly took on a perfect, delicate vase-like form.
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Regardless of how much Raykh agitated the blend, the fluids always reverted to that strange formation.
"I wondered, 'What is happening here?' So, I paced back and forth through the hallways of the Polymer Science and Engineering Department, stopping at my professors' offices to ask if they had any insights," Raykh recounted.
Neither of the professors understood what was happening, but two of them became interested and reached out to their counterparts at Tufts and Syracuse Universities to develop simulations.
"When confronted with something impossible, one must investigate," Russell stated.
To put it briefly, what made it intriguing was that the surfactant ought to have enabled the two liquids to blend together. This aligns with the principles of thermodynamics as described in textbooks. we obey in this house ) the liquid should be a mixture, rather than what appears to be an hourglass figure in its lowest energy state.
Upon examining the interactions attentively, the group discovered that the magnetized nickel effectively heightened the strain between the two components. liquids , instead of decreasing it as is typical.
When you examine the individual nanoparticles of magnetized nickel at the interface between water and oil," said David Hoagland, a professor of polymer science and engineering at UMass Amherst, "you can obtain highly detailed insights into how various structures organize themselves. Here, these particles are so strongly magnetized that they disrupt the emulsification process, an effect governed by the principles of thermodynamics.
As stated by the team, the unusual form it takes is determined by the vessel itself.
Instead of fostering emulsification, interfacially active magnetic particles completely prevent emulsification because they create persistent irregularities at the liquid boundaries through magnetic particle interactions within the plane. These interactions have substantial, appealing, and oriented energies (which depend on how the particles are positioned relative to each other). As a result, this stabilization happens alongside an enhancement in the surface tension,” the researchers explain in their study.
The magnetic interaction’s dipolar anisotropy leads to a chain-like arrangement of particles at the interface, forming pathways substantial enough for easy movement of liquids across touching droplets. This configuration supports rapid equilibrium and re-equilibrium processes within structured liquid surfaces. This was illustrated by the formation of an urn-like phase inside a cylinder. Changes were observed solely due to the wetting characteristics of both the liquid surface and the container walls.
The discovery doesn't have practical applications at the moment; however, Raykh remains optimistic that this previously unobserved state might be explored further, contributing to advancements in soft-matter physics.
The study has been published in Nature Physics .